Advertisement for orthosearch.org.uk
Orthopaedic Proceedings Logo

Receive monthly Table of Contents alerts from Orthopaedic Proceedings

Comprehensive article alerts can be set up and managed through your account settings

View my account settings

Visit Orthopaedic Proceedings at:

Loading...

Loading...

Volume 98-B, Issue SUPP_1 January 2016 The International Society for Technology in Arthroplasty (ISTA), 27th Annual Congress. PART 1.

Ali Abdulkarim Andrew Moriarity Peter Coffey Eoin Sheehan

Introduction

The role of diathermy in orthopaedic surgical practice has increased since its introduction. It is widely used for underlying tissue dissection, cutting, and haemostasis. Previous studies have compared electrosurgical and scalpel incisions in terms of wound infection, wound-related pain, and blood loss. There are well documented hazards associated with diathermy use including burns injury, electrocution, hypoxic stress, inhalation of diathermy plume, and gene mutation. No single study to date has focused on the potential for diathermy tips to cause wound contamination and infection. We sought to identify whether diathermy tips could be possible sources of infection in orthopaedic procedures.

Objectives

To determine the prevalence of bacterial contamination of diathermy tips during orthopaedic surgery and to assess any correlation with surgical site infections.


Ali Abdulkarim Andrew Moriarity Eoin Sheehan

Introduction

Surgical gloves function as a mechanical barrier that reduces transmission of body fluids and pathogens from hospital personnel to patients and vice versa. The effectiveness of this barrier is dependent upon the integrity of the glove. Infectious agents have been shown to pass through unnoticed glove microperforations which have been correlated to the duration of wear. Varying factors may influence the integrity of the glove such as the material, duration of use, activities and fit. Studies have recommended changing gloves 90 minutes into a general surgical operation, however there are no known EBM recommendations in orthopaedic surgery.

Objectives

The aim of our study was to determine whether the intrinsic properties of sterile surgical gloves can be compromised when exposed to common orthopaedic materials in the operating theatre.


Ali Abdulkarim KE Krause Eoin Sheehan

Introduction

Tourniquets have been used for many years during total knee arthroplasty as a means of achieving a bloodless field for better visualization and cement-bond inter-digitation. Controversy has surrounded the necessity for a tourniquet in past years. There are many advantages and disadvantages to using a tourniquet, and one prominent disadvantage is a purported increase in post-operative pain and limitations in range of motion.

Objective

This study examined the literature for assessment of pain and analgesia usage in post-operative patient who have either received no tourniquet during surgery or received variations in both timing and pressure. Secondary outcomes included were functional in nature, namely range of motion and post-operative hospital stay.


Mitsugu Todo Abdul Halim Abdullah Yasuharu Nakashima Yukihide Iwamoto

Bone remodeling effects is a significant issue in predicting long term stability of hip arthroplasty. It has been frequently observed around the femoral components especially with the implantation of prosthesis stem. Presence of the stiffer materials into the femur has altering the stress distribution and induces changes in the architecture of the bone. Phenomenon of bone resorption and bone thickening are the common reaction in total hip arthroplasty (THA) which leading to stem loosening and instability. The objectives of this study are (i) to develop inhomogeneous model of lower limbs with hip osteoarthritis and THA and (ii) to predict the bone resorption behavior of lower limbs for both cases.

Biomechanical evaluations of lower limbs are established using the finite element method in predicting bone remodeling process. Lower limbs CT-based data of 79 years old female with hip osteoarthritis (OA) are used in constructing three dimensional inhomogenous models. The FE model of lower limbs was consisted of sacrum, left and right ilium and both femur shaft. Bond between cartilage, acetabulum and femoral head, sacrum and ilium were assumed to be rigidly connected. The inhomogeneous material properties of the bone are determined from the Hounsfield unit of the CT image using commercial biomedical software. A load case of 60kg body weight was considered and fixed at the distal cut of femoral shaft. For THA lower limbs model, the left femur which suffering for hip OA was cut off and implanted with prosthesis stem. THA implant is designed to be Titanium alloy and Alumina for stem and femoral ball, respectively.

Distribution of young modulus of cross-sectional inhomogeneous model is presented in Fig. 2 while model of THA lower limbs also shown in Fig. 2. Higher values of young modulus at the outer part indicate hard or cortical bone. Prediction of bone resorption is discussed with the respect of bone mineral density (BMD). Changes in BMD at initial age to 5 years projection were simulated for hip OA and THA lower limbs models.

The results show different pattern of stress distribution and bone mineral density between hip OA lower limbs and THA lower limbs. Stress is defined to be dominant at prosthesis stem while femur experienced less stress and leading to bone resorption. Projection for 5 years follow up shows that the density around the greater tronchanter appears to decrease significantly.


Mitsugu Todo Abdul Halim Abdullah Yasuharu Nakashima Yukihide Iwamoto

Effectiveness and long term stability of hip resurfacing and total hip arthroplasty for osteoarthritis patients are still debated nowadays. Several clinical and biomechanical issues have to be considered, including pain relief, return to function, femoral neck fractures, impingement and prosthesis loosening. Normally, patients with hip arthroplasties are facing gait adaptation and at risk of fall. Sudden impact loading and twisting during sideway falls may lead to femoral fractures and joint failures. The purposes of this study are (i) to investigate the stress behavior of hip resurfacing and total hip arthroplasty, and (ii) to predict pattern of femoral fractures during sideway falls and twisting configurations.

Computed tomography (CT) based images of a 54-year old male were used in developing a 3D femoral model. The femur model was designed to be inhomogeneous material as defined by Hounsfield Unit of the CT images. CAD data of hip arthroplasties were imported and aligned to represent RHA and THA femur modelas shown in Fig.1. Prosthesis stem is modeled as Ti-6Al-4V material while femoral ball as Alumina properties. Meanwhile, RHA implant is assigned as Co-Cr-Mo material. Four types of loading and boundary conditions were assigned to demonstrate different falling (FC) and twisting (TC) configurations (see Fig.2). Finite element analysis combined with a damage mechanics model was then performed to predict bone fractures in both arthroplasty models. Different loading magnitudes up to 4BW were applied to extrapolate the fracture patterns.

Prediction of femoral fracture for RHA and THA femurs are discussed in corresponding to maximum principal stress and damage formation criterion. The load bearing strain was set to 3000micron, the physiological bone loading that leads to bone formation. The test strength was wet to 80% of the yield strength determined from the CT images. Different locations of fracture are predicted in each configuration due to different loading direction and boundary conditions as shown in Fig.3. For falling configurations, fractures were projected at trochanteric region for intact and RHA femur, while THA femurs experience fracture at inner proximal region of bone. Differs to twisting configurations, both arthroplasties were predicted to fracture at the distal end of femurs.


Satomi Abe Hitoshi Nochi Takuya Ruike Yusuke Sasaki Hiroshi Ito

Introduction

Malrotation of a femoral component is a cause of patellofemoral maltracking after total knee arthroplasty (TKA). We have developed a balanced gap technique in posterior stabilized total knee arthroplasty (PS-TKA) using an original tensor instrument. One of characteristics of this instrument is the ability to measure gaps even if there is a bone defect, because it has two paddles, and we can attach block augmentations. In addition it can measure the gap after a reduction of the patella with an offset mechanism. In the balanced gap technique, the femoral component rotation is decided by a tibial cut surface and ligaments balance using the tensor device. This study investigated retrospectively whether rotational alignment of femoral component rotation influenced patellofemoral joint congruency in PS- TKA.

Material and Methods

We evaluated the radiographs of 52 knees of 42 patients, who underwent TKA (NexGen LPS-Flex, fixed surface, Zimmer) by one surgeon (S.A.) for osteoarthritis or rheumatoid arthritis. All procedures were performed through a medial parapatellar approach and a balanced gap technique using a developed versatile tensor device. We measured lateral patella tilt and lateral patella shift at post-op. 6 months. To assess the rotational alignment of femoral component rotation, condylar twist angle (CTA) was measured, and to assess the postoperative flexion gap balance, a condylar lift-off angle (LOA) was measured using the epicondylar view radiographs.


Aditya Aggarwal Nagmani Singh Sudesh Pebam

Introduction

Bilateral total knee arthroplasty (TKA) results in substantial perioperative blood loss with increased morbidity. Tranexamic acid (TXA) administration in either intravenous or topical form has been found to be effective in reducing perioperative blood loss. The objective of the present study was to compare the efficacy of topical versus intravenous TXA in reducing perioperative blood loss.

Methods

Prospective, randomized, double-blinded clinical trial was carried out on 70 patients undergoing bilateral TKA, who were divided into two groups. Group I received equivalent dose of TXA intravenously 30 minutes prior to deflation of tourniquet of first knee and another dose repeated after 2 hours. Group 2 received topical TXA in the dose of 15mg/kg dissolved in100 ml of normal saline which was applied into the joint for 10 minutes at the end of implant insertion. Outcome measures were total blood loss as (calculated from the difference between preoperative and postoperative day3 haemoglobin (Hb) or Hb prior to transfusion), total drain output and amount of blood transfusion.


Aditya Aggarwal Sreekanth R Rajoli Vivekanand Jha Mahesh Prakash

INTRODUCTION

There is no effective therapy available today that alters the pathobiologic course of osteoarthritis. Recent advances have shown Mesenchymal stem cells to be a potential disease modifying treatment. Considering the tissue differentiation property and vast paracrine effects of MSCs we proposed the present study to find out the safety and efficacy of Mesenchymal stem cells in osteoarthritis of knee joint.

METHODS

12 patients with grade 1and2 bilateral osteoarthritis knee (Ahlbacks radiological grading) were selected. 8–10 ml of bone marrow was aspirated under strict aseptic precautions from the iliac spine. After the stem cell culture and expansion for 4–6 weeks the MSC suspension in 10xPBS was injected directly into the 24 knees by lateral approach. The outcome was evaluated by modified VAS score, WOMAC score, KOOS and MRI measurement of knee articular cartilage integrity by the modified WORMS score.


Luciano Agnello Linda Pomeroy Ali Bajwa Richard Villar

Background

Hip replacement surgery is an effective treatment, however quantitative outcome does not necessarily delineate the true picture. It is important to triangulate data methods in order to ascertain important contextual factors that may influence patient perception.

Aims

The aim of the current study was to explore the patient perception on resurfacing hip arthroplasty (RHA) and mini-hip arthroplasty (MHA) in a unique cohort where each patient has received a resurfacing on one side and a mini-hip on the contralateral side using both quantitative and qualitative measures (Fig. 1).


Takashi Aki Takehiko Sugita Atsushi Takahashi Naohisa Miyatake Eiji Itoi

Introduction

The popliteus tendon is a component of the posterolateral corner of the knee, which controls the external rotation of the tibia. In our clinical practice, the femoral footprint of the popliteus tendon is occasionally excised as the bone is resected during total knee arthroplasty (TKA). Although the excision of the popliteus tendon femoral footprint could result in excessive external rotation of the tibia and may have adverse effects on the long-term outcomes of TKA, little attention has been paid to the popliteus tendon femoral footprint during TKA. The purpose of the present study is to assess the frequency of the excision and its associated risk factors.

Methods

One hundred eleven knees of 90 patients with varus knee osteoarthritis who underwent primary TKA were included in the present study. There were 13 males and 77 females, and their average age was 74 years. The NexGen knee replacement system (Zimmer, Warsaw, IN, USA) was used in all cases. The excision of the popliteus tendon femoral footprint was intraoperatively evaluated, and the patients were divided into three groups depending on the status of the femoral footprint, i.e., the preserved, partially excised, and completely excised groups. The thickness of the distal femoral osteotomy, femoral component size, and background data including height, body weight, gender, and age were compared among these groups. Analysis of variance followed by Student–Newman–Keuls test were used to compare the continuous values and ordinal scales. Gender was compared using Fisher's exact test and residual analysis. Statistical significance was set at p < 0.05.


Hesham Al-Khateeb Tahir Mahmud Steven MacDonald James P McAuley

Objectives

Porous metal surfaces have been a popular option for acetabular component fixation in total hip arthroplasty (THA). New THA component designs are introduced periodically with the expectation of better wear properties and survivorship. Since its approval for use in 2002 there have been few clinical outcome studies published on the Pinnacle acetabular cup system. We hypothesised that the hemispherical porous coated Pinnacle acetabular cup system with a range of cup options and bearing surfaces would give us predictably good fixation and survivorship at five years post implantation.

Materials and Methods

A total of 1391 Pinnacle acetabular cups (De Puy, a Johnson & Johnson company, Warsaw IN) were implanted between the period March 2003 to August 2011 by four senior surgeons. There were a total of 29 patients requiring revision surgery. Of these revisions, 23 were excluded from the final analysis. Sixteen were for early infection requiring debridement of the hip joint and exchange of the modular liner and femoral head. Five patients sustained femoral peri-prosthetic fractures requiring further surgery with retention of the acetabular component in all cases. Of the remaining 8 revision cases, only 6 had more than two years follow-up. All patients had pre and post-operative Harris hip scores, WOMAC and SF-12 scores. All patients were assessed with serial radiographs immediately post-operatively, 3 months, 1 year, 2 years, every 2 years thereafter. Component migration and revisions (excluding infection and peri-prosthetic fractures) are reported as failures. Post-operative radiographs were evaluated for component migration. Kaplan-Meier survivorship curves were drawn to show survivorship for cup type and bearing type.


Hesham Al-Khateeb Tahir Mahmud Douglas Naudie Richard W McCalden

INTRODUCTION

The development of new bearing surfaces for total joint replacement is constantly evolving. Oxidized zirconium (Oxinium) has been introduced for use in both total hip arthroplasty (THA) and total knee arthroplasty (TKA). The aetiology of wear is multifactorial and includes adhesive, abrasive, third-body and fatigue wear mechanisms. Oxinium femoral components have demonstrated clear improvements in wear characteristics in-vitro. The purpose of this prospective study was to evaluate the mid-term (minimum 5 year) clinical and radiographic results and survivorship of the Genesis II™ knee implant system using an Oxinium femoral component.

METHODS

Between January 2001 and December 2008, 382 Genesis II Oxinium (Smith & Nephew) primary total knee arthroplasties (TKA) (313 patients) were implanted at our institution. A comparison with a cohort of 317 patients (382 knees) who received a Genesis II knee implant using a ‘conventional’ cobalt-chrome (Co-Cr) femoral component was performed during the same time period. Prospective data was collected on all patients including demographics (age, BMI, diagnosis) as well as pre and postoperative clinical outcome scores (SF-12, WOMAC, and knee society clinical rating scores (KSCRS). Radiological analysis for evidence of osteolysis and loosening was performed in all patients. Comparisons were performed to determine differences between the Oxinium and Cobalt Chrome cohorts. Kaplan-Meier survival analysis was performed to show cumulative survival over time. Failure was defined as femoral component revision due to any cause.


Hesham Al-Khateeb James Howard Douglas Naudie Richard W McCalden Steven MacDonald

Introduction

Total knee arthroplasty (TKA) has proven clinical success with reported longterm survivorship of 92% in the elderly population. Concerns regarding increased loosening rates and potential need for multiple revision surgeries in patients younger than 60 years have traditionally discouraged TKA in younger patients. The purpose of this study was to review the longterm clinical and radiographic results of patients under the age of 45 yrs who underwent a total knee replacement.

Materials and Methods

A retrospective review of our institutional database was performed between January 1996 and December 2004 The criteria for inclusion in the study were as follows: age 45 years or younger at index arthroplasty, cemented condylar prosthesis, and a minimum follow-up of 9 years. A total of 39 consecutive primary cemented condylar knee arthroplasties in patients with end stage arthritis were performed in 36 patients who were 45 years or younger. The median length of followup was 13.6 years. There were 18 men and 21 women. The mean age was 40.6 years (range, 28–44). There were 23 right, 16 left, and 3 bilateral procedures. The mean body mass index was 31.2 kg/m2

Clinical and radiological evaluations were performed before surgery and at 6 weeks, 3 months, 1 year and every 2 years subsequently. Knee scores were calculated using the Knee Society Clinical Rating Scores (KSCRS), SF-12 and WOMAC scores to assess pre, and post-operative function. Postoperative anteroposterior and lateral views were assessed for femoral and tibial component position, alignment, and presence or progression of radiolucent lines at the bone-cement and prosthesis-cement interfaces

Statistical analysis was performed using the 2-sample test or Wilcoxon rank sum test for comparison of continuous variables. Kaplan-Meier analysis of implant survival was performed with failure defined as femoral component revision due to any cause.


Hesham Al-Khateeb Matthew Teeter Douglas Naudie Richard W McCalden

Introduction

The development of new bearing surfaces for total joint replacement is constantly evolving. Oxidized zirconium (Oxinium) has been introduced for use in total hip arthroplasty (THA) and total knee arthroplasty (TKA). One of the most common causes of failure of THA is aseptic loosening secondary to polyethylene wear debris. The aetiology of wear is multifactorial and includes adhesive, abrasive, third-body and fatigue wear mechanisms. Oxidized zirconium is a relatively new material that features an oxidized ceramic surface chemically bonded to a hard metallic substrate. This material possesses the reduced polyethylene wear characteristics of a ceramic, without the increased risk of implant fracture While short-term results of oxidized zirconium in THA have been reported, there have been no reports on retrieved highly cross linked PE articulating with Oxinium headsObjectives:

Objectives

The purpose of this study was to compare matched pairs of retrieved highly cross-linked polyethylene (XLPE) acetabular liners with OxZr and CoCr articulation. The liners were examined for evidence of wear damage, including articular surface damage, impingement, screw-hole creep, and rim cracks


Alessandro Carcangiu Carmelo D'arrigo Alberto Maria Bonifazi Stefania De Sanctis Raffaella Alonzo Andrea Setini Andrea Ferretti

Background

Limb length discrepancy after total hip replacement is one of the possible complications of suboptimal positioning of the implant and cause of patients dissatisfaction.

Computer assisted navigation become affirmed in last years for total hip replacement surgery and it is also used for the evaluation of the intra-operative limb length discrepancy.

The purpose of this study is to verify the reliability of a navigation system with a dedicated software in intraoperative evaluation of limb lengthening and offset as compared with manual technique.

Methods

Forty patients who underwent a Total Hip Arthroplasty in our institution were entrolled in this study. Twenty patients were evaluated with pre operative manual planning (group A) and treated with hand positioning of femoral stem. Twenty Patient were evaluated with preoperative manual planning and treated with Computer assisted navigation of Stem (group B).

Mean operating time and blood loss were analyzed. Radiological and clinical follow up was made at 1, 3, 6 and 12 months postoperative to assess any mismatch of implant, complications and clinical results that was measured with Harris Hip Score.


Christopher Anderson Martin Roche Gregory Golladay Leah Elson

INTRODUCTION

Achieving balance in TKA is critical in assuring favorable outcomes. But, in order to achieve quantifiably balanced loading values, is it more advantageous to make bony corrections or release soft-tissue? The answer to this question will be paramount in evaluating the most appropriate surgical techniques for use with new dynamic technology, thereby maximizing favorable clinical outcomes. Therefore, the purpose of this investigation was to evaluate a possible quantitative loading threshold, using intraoperative sensors, which may dictate surgical correction of bone versus soft-tissue release.

METHODS

A retrospective analysis of 122 multicenter patients, in receipt of sensor-assisted primary TKA, was conducted. 40 lbs. was used as a threshold, above which bone was corrected; below which soft-tissue was corrected. All patients were categorized in to the following groups: Group A – candidates for bony correction, but received soft-tissue correction; Group B – candidates for soft-tissue/receiving soft-tissue; Group C – candidates for bony correction/receiving bony correction.


Wataru Ando Kengo Yamamoto Masaharu Aihara Tsuyoshi Koyama Yoshichika Hashimoto Takashi Tsujimoto Kenji Ohzono

Metal on metal total hip arthroplasty (MoM THA) provides the potential improvement in articular wear. However, several adverse events including pseudotumor had been reported. Magnetic resonance imaging (MRI) was considered to be the proposal tool for detection of pseudotumor after MoM THA. In this study, we performed the screening of pseudotumor after MoM THA using the MRI.

We studied 43 patients with M2a Magnum® (Biomet) and 34 patients with M2a Taper® (Biomet) of MoM THA from December 2009 to December 2011 with follow-up of 2.5 years (2.0–4.0 years) after surgery. MRI assessments were performed at a mean of 2.1 years postoperatively. Pseudotumor findings were graded using Anderson classification (Skeletal Radiol, 2011: 40; 303). Age, sex, height, weight, Harris Hip Score, EQ5D satisfaction score, UCLA activity score, and blood metal ion levels were evaluated.

The prevalence of pseudotumor was 27.2%; 56 normal (Type A), 13 mild (C1), 8 moderate (C2) and none were graded severe (C3). Weight and BMI in the mild group was significantly higher than those in normal. There was no significant difference in age, sex and height among these groups. With regard to Harris Hip score, pain and ROM score in moderate group was significantly lower than that in normal and mild group. EQ5D satisfaction score and UCLA activity score showed not significant differences among groups. 3.01±3.32 μg/L of blood cobalt ion levels in the moderate groups was significantly higher than 0.97±0.64 μg/L in normal group. Blood cobalt ion levels of 1 mild and 2 moderate were over the threshold of 7 μg/L. These patients were implanted with M2a Taper, not M2a Magnum. 14% of the prevalence in the patients with M2a Magnum was significantly lower than 41% in the patients with M2a Taper. No revision surgeries were required.

The patients with no pseudotumor did not show the increase of blood metal ion. Contrarily, several patients showed the increase of blood metal ion in case of detecting pseudotumor. MRI assessments were useful for screening of pseudotumor after MoM THA and blood metal ion should be investigated for patients with mild and moderate pseudotumor in MoM THA.


Laurent Angibaud Ralph A Liebelt Bo Gao Scott Gulbransen Xeve Silver

Introduction

Clinical outcomes for total knee arthroplasty (TKA) are especially sensitive to lower extremity alignment and implant positioning.1 The use of computer-assisted orthopaedic surgery (CAOS) can improve overall TKA accuracy.2 This study assessed the accuracy of an image-free CAOS guidance system (Exactech GPS, Blue-Ortho, Grenoble, FR) in both a synthetic leg with a normal mechanical axis and legs with abnormal mechanical axis.

Materials and methods

A high-resolution 3D scanner (Comet L3D, Steinbichler, Plymouth, MI) was used to scan varus-deformed (n=12), neutral (n=12), and valgus-deformed (n=4) knee inserts (Mita M-00566, M-00598, M-00567; respectively, Medical Models, Bristol, UK) and collect pre-identified anatomical landmarks prior to using the models to simulate knee surgery. The image-free CAOS guidance system was then used to acquire the same landmarks. After adjusting the position and orientation of the cutting block to match the targets, bone resections were performed, and the knee models were re-scanned. The 3D scans made before and after the cuts were overlaid and the resection parameters calculated using the pre-identified anatomical landmark data and advanced software (UG NX, Siemens PLM, Plano, TX). Data sets obtained from the 3D scanner (see Figure 1A) were compared with data sets from the guidance system (see Figure 1B). Given the accuracy of the 3D scanner (<50μm), its measurements were used as the baseline for assessing CAOS system error.


Laurent Angibaud Ralph A Liebelt Bo Gao Xeve Silver

Introduction

From pre-operative planning to final implant cementation, total knee arthroplasty (TKA) preparation is a succession of many individual steps, each presenting potential sources of error that can result in devices being implanted outside the targeted range of alignment. This study assessed alignment discrepancy occurring during different TKA steps using an image-free computer-assisted orthopaedic surgery (CAOS) guidance system (Exactech GPS, Blue-Ortho, Grenoble, FR) in normal and abnormal mechanical axis.

Materials and methods

We used a commercially available artificial leg (MITA trainer leg M-00058, Medical Models, Bristol, UK) able to receive (neutral / varus / valgus) knee inserts simulating the proximal tibia and distal femur. A pre-surgical profile was established to define resection parameters for the proximal tibial and distal femoral cuts (Figure 1A). Data from the guidance system were collected at three separate steps: (1) cutting block adjusted but not pinned to the bone (Figure 1B), (2) cutting block adjusted and pinned to the bone (Figure 1C), and (3) after the cuts were checked (Figure 1D). These data were then compared to the resection target parameters to track potential dispersions occurring during the process.

Due to the amount of data (i.e., four studied resection parameters per bone, three operative steps, and three knee model types), the authors introduced an “error index”, which was a unitless indication of overall error magnitude obtained by averaging the absolute values of all linear and angular measurement errors. Due to knee model dimensions (∼55 mm), the authors equally considered linear and angular measurement values (i.e., 1 mm equivalent to 1°).


Laurent Angibaud Ralph A Liebelt Bo Gao Xeve Silver

Introduction

An emerging consensus in the surgical specialties is that skill acquisition should be more emphasized during surgical training.1 This study was an attempt to evaluate the effects of repetitive practices using an image-free computer-assisted orthopaedic surgery (CAOS) guidance system (Exactech GPS, Blue-Ortho, Grenoble, FR) on both technical and cognitive skills.

Materials and methods

A senior knee replacement surgeon with limited previous experience with the CAOS system performed a series of consecutive simulated knee surgeries using a commercially available artificial leg (MITA trainer leg M-00058, Medical Models, Bristol, UK).

In order to assess the effects repetitive practice has on technical skills, we evaluated two indexes:

Error index: A unitless indication of overall error magnitude obtained by averaging the absolute values of all linear and angular measurement differences between targeted and checked cuts.

Time index: An indication of the time required to acquire landmarks, adjust the custom blocks, and make cuts.

In order to assess the effect repetitive practice has on cognitive skills, we evaluated the number of times the surgeon elected to deviate from pre-surgical planning or re-acquire landmarks.

We evaluated these parameters for three chronological and consecutive groups of simulated surgeries: Group A (knee models #1 to #10), Group B (knee models #11 to #20), and Group C (knee models #21 to #28).


Hideyuki Aoki

Correct rotational alignment of the femoral component is one of the most important elements in successful total knee arthroplasty. The surgical epicondylar axis is a well-known reliable landmark for a total knee arthorplasy. However, sometimes it is difficult for surgeon to define where a sulcus is, thus, hard to define a surgical epicondylar axis during a surgery. This Study evaluated the new reference of axis “Lateral Condylar Axis (LCA)” for the distal femur. The LCA is defined by the angle between the surgical epicondyalr axis and the Lateral Condylar Axis. To evaluate the consistency of this angle through ages, genders and femoral-tibia angle, this study also measured the angles between the surgical epicondylar and the anteroposterior asix and the surgical epicondylar and the posterior condaylar axis. By evaluating out the correlations and comparing the figure between measurements using the Student test, this study suggests that the Lateral Condylar Axis is a reliable landmark to properly rotate the femoral component and is easier to define during a surgery. The 59 knees out of 41 patients data was measured in 2011 – 2012.


Masato Aratake Naoto Mitsugi Naoya Taki Hirohiko Ota Kentaro Shinohara Yohei Sasaki Tomoyuki Saito

Introduction

Selection of an optimum thickness of polyethylene insert in total knee arthroplasty (TKA) is important for the good stability and range of motion (ROM). The purpose of this study is to investigate the amount of change of ROM as the thickness of trial insert increase.

Material and Method

The study included 86 patients with 115 knees undergoing TKA from October 2012 to February 2014. There were 17 men and 69 women with an average age of 75±8 (58–92) years. The implants posterior stabilized knee (Scorpio NRG, Stryker) was used and all prostheses were fixed with cement. The ROM was measured by the goniometer under the general anesthesia at the time of operation in increments of 1°. Preoperative flexion angle was measured by passively flexing the patient's hip 90 degrees and allowing the weight of the leg to flex the knee joint (Lee et al 1998). Extension angle was measured by holding the heel and raising the leg by another examiner. During TKA, flexion and extension angle was measured in a similar manner when each insert trial (8, 10, 12, and 15mm) was inserted. After the wound closure and removing the draping, ROM was measured again. Statistical analysis of range of motion was performed using a paired t-test to determine significance


Ron Arbel Nehemia Blumberg Eran Linder-Ganz

The purpose of this study was to evaluate short-term clinical and MRI outcome of a polycarbonate-urethane meniscus implant for the treatment of medial compartment pain in middle aged patients.

In the younger population, (<40 yrs.) surgical options e.g., allograft transplants and artificial scaffolds are available and have been shown to be effective. For middle aged patients, the clinical benefit from surgical intervention of a degenerated meniscus has only been reported in a fraction of the patients. However, these patients are still too young for more aggressive treatments such as unicompartmental or total knee arthroplasty.

The meniscus implant is a non-degradable polymer-based spacer which is inserted into the medial compartment of the knee between the tibia and femur by a mini-arthrotomy, without requiring attachment or bone resection. It was hypothesized that the implant could relieve pain by restoring the pressure distribution function. This paper presents the first experience of 3 Israeli sites (out of 7 sites participating in the study).

Thirty patients aged 36 to 70 years were treated with the implant after signing an informed consent and meeting the criteria defined in the Ethics Committee approved protocol. All of the patients reported medial knee pain which was associated with either a severely degenerated meniscus (∼25%) or post-meniscectomy knee pain (∼75%). Patients with evidence of grade IV medial articular cartilage loss or instability were excluded from the study. Primary clinical outcome was measured by the KOOS scale over 12 months, with secondary outcomes measured by IKDC subjective, EQ-5D and VAS questionnaires for pain. Serial MRI scans were taken at 6 weeks and 12 months of follow-up to evaluate the condition of the articular cartilage.

The patients included in this study showed a considerable clinical improvement after the procedure. Significant pain relief was indicated by both KOOS pain subscale and VAS scores after 6 months follow up, and patient activity levels were also found to be higher following implantation. The first MRI findings from this study were considered to be promising since no signs of deterioration of the surrounding cartilage or of the device were observed. So far, one case of implant dislocation and two cases of infection have occurred among the 35 patients.

This study was designed to evaluate and obtain reasonable assurance of the safety, effectiveness, and risk/benfit ratio of a novel implant in the treatment of a challenging patient cohort. The short-term outcomes are promising.


Jean-Noel Argenson Sebastien Parratte Xavier Flecher Jean-Manuel Aubaniac

Treatment of osteoarthritis of the knee remains a challenging problem since the evolution of the disease may be different in each compartment of the knee, as well as the state of the ligaments. Total knee arthroplasty may provide a reliable long-lasting option but do not preserve the bone stock. In another hand, compartmental arthroplasty is a bone and ligament sparing solution to manage limited osteoarthritis of the knee affecting the medial, lateral or the patello-femoral compartment.1, 2, 3

Patient's selection and surgical indication are based on the physical examination and on the radiological analysis including full-length x-rays and stress x-rays. Clinical experience has shown the need for high flexion in patients who have both high flexibility and a desire to perform deep flexion.

Additionally the shape differences related to anatomy or the patient expectations after the surgery may also affect the surgeon decision. 4

The limited incision into the extensor mechanism allows a quicker recovery which represents a functional improvement for the patient additionally to the cosmetic result. A dedicated physiotherapy starting on the following day allowing weight bearing exercises protected by crutches and focusing on early mobilization and range of motion combined to a multimodal pain management approach is critical despite the type of individualized solution chosen for the patient knee. 5

Since bony landmarks may be different form a patient to another one as well as anatomical shapes, several tools have been developed in order to provide the surgeons an assisted tool during the surgery adapted to each knee, this include navigation, patient specific instrumentation and robotic surgery.


Jean-Noel Argenson Xavier Flecher Sebastien Parratte Jean-Manuel Aubaniac

Improving the adaptation between the implant and the patient bone during total hip arthroplasty (THA) may improve the survival of the implant. This requires a perfect understanding of the tridimensional characteristics of the patient hip. The perfect evaluation of the tridimensional anatomy of the patient hip can be done pre-operatively using X-rays and CT-scan. All patients underwent a standard x-rays evaluation in the same center according to the same protocol. Pre-operatively, the frontal analysis of the hip geometry was performed and the optimal center of rotation, CCD angle, neck length and lever arm was analyzed to choose the optimal solution for proper balance of the hip in order to obtain adequate range of motion, appropriate leg length, and correct tension of the abductors muscles. Standard or lateralized monoblock stems can be valid or modular neck shape can be choosen among 9 available shape. These 9 frontal shapes are available in standard, anteverted or retroverted shapes, leading to 27 potential neck combinations. In case of important hip deformation, a custom implant can be used in order to balance the extra-medullar geometry without compromising the intra-medullary adaptation of the stem.

We prospectively included 209 hips treated in our institution with total hip arthroplasty performed using a supine Watson-Jones approach and the same anatomic stem. The mean patient age was 68 years and the mean BMI 26 Kg/m². Intra-operatively the sagittal anatomy of the hip was analyzed and standard, ante or retro modular necks were tested for the frontal shape defined pre-operatively.

According to the pre-operative frontal planning, non-standard necks were required in 24 % of the cases to restore the anatomy of the hip. Intra-operatively, a sagittal correction using anteverted neck was required in 5% of the cases and retroverted necks in 18% of the cases. Harris hip score improved from 56 to 95 points at min. 5 year follow-up. No leg length discrepancy greater than 1 cm was observed. Restoration of the lever arm (mean 39.3 mm, range 30 to 49 mm) and of the neck length (55.2, range 43 to 68 mm) was adapted for 95% compared to the non operate opposite side. Disturbed anatomy like in DDH or post-traumatic cases may require additional solutions to balance the hip such combined osteotomy or customized stem and neck.


Christina Arnholt Sevi Kocagoz Daniel MacDonald Jeremy Gilbert Javad Parvizi Arthur L Malkani Gregg Roger Klein Matthew Kraay Clare Rimnac Steven Kurtz

Introduction

The release of metal debris and ions has raised concerns in joint arthroplasty. In THA metal debris and ions can be generated by wear of metal-on-metal bearing surfaces and corrosion at modular taper interfaces, currently understood to be mechanically assisted crevice corrosion (MACC) [1]. More recently, inflammatory-cell induced corrosion (ICIC) has been identified as a possible source of metal debris and/or ions [2]. Although MACC has been shown to occur at modular junctions in TKA, little is known about the prevalence of other sources. The purpose of this study was to determine the sources of metallic debris and ion release in long-term implanted (in vivo > 15y) TKA femoral components. Specific attention was paid to instances of ICIC as well as damage at the implant-bone interface.

Methods

1873 retrieved TKA components were collected from 2002–2013 as part of a multi-center, IRB-approved retrieval program. Of these, 52 CoCr femoral condyles were identified as long term TKA (Average: 17.9±2.8y). These components were predominantly revised for loosening, PE wear and instability. 40/52 of the components were primary surgeries. Components were examined using optical microscopy to confirm the presence of 5 damage mechanisms (polyethylene failure, MACC corrosion of modular tapers, corrosion damage between cement and backside, third-body wear, and ICIC). Third-body wear was evaluated using a semi-quantitative scoring method based on the percentage of damaged area. A score of 1 had minimal damage and a score of 4 corresponded to severe damage. Polyethylene components were scored using the Hood method and CoCr components were scored similarly to quantify metal wear. The total area damaged by ICIC was quantified using photogrammetry. Images were taken using a digital SLR with a calibrated ruler in the same focal plane. Using known pixel dimensions, the ICIC damaged area was calculated.


Full Access
Bakul Arora Nilen Shah

Background

Subvastus approach for Total Knee Arthropalsty (TKA) allows a faster recovery. It is traditionally not utilized for revision surgeries because of difficulty in exposure of the knee and eversion of the patella. It is considered to have limited indications. We hypothesized that revision TKA should not really pose a problem as the exposure gained is adequate with added advantage of preserving the extensor mechanism, thereby allowing faster functional recovery. We present an analysis of the use of subvastus approach for revision TKAs.

Materials and methods

50 patients (50 knees) 37 females + 13 males with mean age 68 years underwent revision total knee arthroplasty (TKA) by subvastus approach between January 2006 to January 2013. All patients were prospectively evaluated by pre- and postoperative Knee Society and function score. The average follow-up was 24 months (range from 1 to 3 years) with minimum 1 year follow-up. The indications for revisions were aseptic loosening (20 knees), infection (12 knees), instability (12 knees) and peri-prosthetic fractures (6 knees). Constrained condylar prosthesis (43 knees), hinged prosthesis (6 knees) and custom made prosthesis (1 knee) were fixed using the subvastus approach. Infected knees underwent one or two staged revisions.


Bakul Arora Nilen Shah

Background

A grossly deformed knee is believed to be an indication for PS -TKA. However, the role CR-TKA in such knees is unclear in the literature. Considering the obvious advantages of CR, we analysed the mid term follow up of CR knees in gross deformities.

Materials and Methods

1590 patients (1740 knees) underwent TKA between January 2011 to December 2012, out of which 570 knees had gross deformity (varus > 15°, FFD > 10°, valgus > 10°, recurvatum > 10). CR-TKA was performed for 540 knees and were included in our study. Subvastus approach was used for all knees. Average age being 68 years, mean BMI being 32 and average weight 70 kgs. Intraoperatively, POLO test was used to ensure PCL stability, further confirmed by direct palpation. Femoral roll-back was found adequate.


Shigeki Asada

The alignment of the knee following total knee arthroplasty (TKA), especially tibial alignment, is a major factor determining the long-term survival of the prosthesis. A disadvantage of using extramedullary alignment guides of the tibia for TKA is the difficulty in correctly identifying the ankle center, and surgeons cannot construct the tibial mechanical axis correctly without the correct location of the ankle center. Although numerous studies have reported bony and soft tissue landmarks for determining the ankle center, a consensus has yet to be reached regarding this matter. This problem is complicated by rotational mismatch between the knee and ankle joint. Because it is difficult to frontalize the knee and ankle joints simultaneously on the same frontal plane. When using extramedullary alignment guides of the tibia, the guides should be applied to the tibia while keeping the knees frontal. The purpose of this study was to determine the position of the ankle center, which is useful for setting extramedullary alignment guides, by using CT data of osteoarthritic knees.

CT data of fifty patients (fifty knees) with varus osteoarthritic knees for primary TKA were retrospectively analyzed. Tibial anteroposterior (AP) axis and transmalleolar axis (TMA) were used as reference axes of the knee and ankle joint, respectively. When using above these reference axes, the offset distance from the bimalleolar center was measured as the position of the ankle center. The angular errors were defined as the varus angle of the proximal tibial cut caused by this offset distance when the position of the ankle center was regarded as the bimalleolar center.

The position of the ankle center was 1.5 ± 1.2 mm and 2.3 ± 1.5 mm medial to the bimalleolar center with reference to tibial AP axis and TMA, respectively. There was a significant difference between the position of the ankle center with respect to the tibial AP axis and with respect to the TMA (p < 0.01). The mean angular error with respect to the tibial AP axis was 0.3 ± 0.2 °, and the value with respect to TMA was 0.4 ± 0.2 °. The maximum varus angular error along tibial AP axis was less than 0.7 degrees.

The positions of the ankle center differed according to the reference axis. Since the angular error was small enough, the bimalleolar center along the tibial AP axis could be used as the ankle center in TKA patients with osteoarthritis knees.


Tamon Asano Michiaki Takagi Atsushi Narita Yuya Takakubo Akemi Suzuki Kan Sasaki Hiroharu Oki

Background

A navigation system is useful tool to evaluate the intraoperative knee kinematics. Rheumatoid arthritis (RA) patients often need to have TKA operation, however, there are few TKA kinematics studies comparing RA and Osteoarthritis (OA) patients.

Objective

The purpose of this study was to evaluate intraoperative TKA kinematics, and to describe the difference of kinematics between RA and OA patients.


Kaitlin Carroll Erik Schnaser Hollis Potter Michael B. Cross

Introduction

The current recommendation by the AAOS in the 2010 clinical practice guidelines for the use of MRI to diagnose a periprosthetic joint infection (PJI) is “inconclusive” given the lack of evidence to support its use. The purpose of this study was to determine the utility of MRI with metal reduction artifact sequencing in diagnosing a periprosthetic joint infection (PJI) after total hip arthroplasty (THA).

Methods

176 patients who underwent MRI with multi-acquisition variable resonance image combination (MAVRIC) to reduce metal artifact for a painful THA between the years of 2009–2013 were retrospectively evaluated. All MRIs were read by one of four radiologists with extensive experience in interpreting MRIs after THA. All MRIs were performed using a 1.5 Tesla magnet. Of the 176 patients examined, 16 patients were found to have a deep periprosthetic joint infection using Musculoskeletal Infection Society (MSIS) criteria after the MRI was performed. MRI reads were classified as either positive (read as “evidence of active infection” or “suspicious for infection”) or negative (read as no evidence of infection). Only one patient who had a positive MRI read was excluded because of loss to followup after the MRI was performed.


Kaitlin Carroll Jared Newman Amethia Holmes Alejandro Gonzalez Della Valle Michael B. Cross

Introduction

Stiffness after total knee arthroplasty is a common occurrence. Despite its prevalence, little is known as to which patients are at risk for poor range of motion after total knee arthroplasty. The purpose of this study was to determine the risk factors for manipulation under anesthesia (MUA) after total knee arthroplasty (TKA).

Methods

Using a single institution registry, 160 patients who underwent a manipulation under anesthesia after total knee arthroplasty between 2007 and 2013 were retrospectively evaluated. Each patient was 1:1 matched by age, gender and laterality to a control group of 160 patients who did not require MUA after TKA. Risk factors for MUA were assessed, and included medical co-morbidities, BMI, prior operations, and preoperative range of motion.


Mamadou Bah Junfen Shi Markus Heller Yanneck Suchier Fabien Lefebvre Philippe Young Leonard King Doug Dunlop Mick Boettcher Edward Draper Martin Browne

There is a large variability associated with hip stem designs, patient anatomy, bone mechanical property, surgical procedure, loading, etc. Designers and orthopaedists aim at improving the performance of hip stems and reducing their sensitivity to this variability. This study focuses on the primary stability of a cementless short stem across the spectrum of patient morphology using a total of 109 femoral reconstructions, based on segmentation of patient CT scan data. A statistical approach is proposed for assessing the variability in bone shape and density [Blanc, 2012]. For each gender, a thousand new femur geometries were generated using a subset of principal components required to capture 95% of the variance in both female and male training datasets [Bah, 2013]. A computational tool (Figure 1) is then developed that automatically selects and positions the most suitable implant (distal diameter 6–17 mm, low and high offset, 126° and 133° CCD angle) to best match each CT-based 3D femur model (75 males and 34 females), following detailed measurements of key anatomical parameters. Finite Element contact models of reconstructed hips, subjected to physiologically-based boundary constraints and peak loads of walking mode [Speirs, 2007] were simulated using a coefficient of fricition of 0.4 and an interference-fit of 50μm [Abdul-Kadir, 2008]. Results showed that the maximum and average implant micromotions across the subpopulation were 100±7μm and 7±5μm with ranges [15μm, 350μm] and [1μm, 25μm], respectively. The computed percentage of implant area with micromotions greater than reported critical values of 50μm, 100μm and 150μm never exceeded 14%, 8% and 7%, respectively. To explore the possible correlations between anatomy and implant performance, response surface models for micromotion metrics were constructed using the so-called Kriging regression methodology, based on Gaussian processes. A clear nonlinear decreasing trend was revealed between implant average micromotion and the metaphyseal canal flare indexes (MCFI) measured in the medial-lateral (ML), anterio-posterior (AP) and femoral neck-oriented directions but also the average bone density in each Gruen zone. In contrast, no clear influence of the remaining clinically important parameters (neck length and offsets, femoral anteversion and CCD angle, standard canal flares, patient BMI and weight or stem size) to implant average micromotion was found. In conclusion, the present study demonstrates that the primary stability and tolerance of the short stem to variability in patient anatomy were high, suggesting no need for patient stratification. The developed methodology, based on detailed morphological analysis, accurate implant selection and positioning, prediction of implant micromotion and primary stability, is a novel and valuable tool to support implant design and planning of femoral reconstructive surgery.


Bryan McEntire B. Sonny Bal Alan Lakshminarayanan Ryan Bock

It has been seven years since silicon nitride (Si3N4) was first proposed as a new bearing material for total hip arthroplasty [1]. Although its introduction into this application has been hampered by regulatory and clinical hurdles, it remains a strong candidate for advancing the state of care in patients undergoing joint replacement. Si3N4 has a distinctive set of properties, such as high strength and fracture toughness, inherent phase stability, low wear, scratch resistance, biocompatibility, hydrophilicity, excellent radiographic imaging, and bacterial resistance, many of which are not fully realized with other bioceramics. This combination of properties is desirable for demanding structural implants in the hip, knee and other total joints. Of foremost concern to clinicians is the wear behavior of any new or novel bearing material. Minimization of wear debris and prevention of corresponding osteolytic lesions are essential regardless of whether the artificial implant is articulating against itself, a metallic or polymeric counterpart. In this regard, Si3N4 may have a unique advantage. Other bearing couples rely solely on the presence of a biologic lubricating film to minimize erosive wear. However, Si3N4 forms a tribochemical film between the articulation surfaces consisting of silicon diimide Si(NH)2, silicic acid Si(OH)4, and ammonia groups NH3, NH4OH. Depending upon the bearing couple, this tribochemical film generally produces low friction. It is self-replenishing and resorbable, leading to the minimization of wear debris within the joint capsule. In this paper, we will review the essential physical, mechanical, and surface chemistry of Si3N4, and contrast these properties with other available bioceramics. Results from hip simulator testing of Si3N4 femoral heads on conventional and highly cross-linked polyethylene will be presented and discussed. Data will demonstrate that various Si3N4 bearing couples have wear comparable to other bioceramics. Microscopy and spectroscopic examinations of surfaces will provide a view of the surface stoichiometry and chemical stability of Si3N4 in comparison to other bioceramics. Laboratory friction tests will be reported, which show that the tribochemistry of the lubricating film generated by Si3N4 favors the use of highly cross-linked polyethylene as a counterface material. Overall results will demonstrate that silicon nitride is poised to become a new generation biomaterial for total joint arthroplasty.


Scott Banks Mohamed Imam Amanda Eifert Richard E Field

Introduction

Total knee arthroplasty (TKA) designs evolve as evidence accumulates on natural and prosthetic knee function. TKA designs based upon a medially conforming tibiofemoral articulation seek to reproduce essential aspects of normal knee stability and have enjoyed good clinical success and high patient satisfaction for over two decades. Fluoroscopic kinematic studies on several medially conforming knee designs show extremely stable knee function, but very small ranges of tibial axial rotation compared to healthy knees. The GMK Sphere TKA is a recent evolution in medially-conforming TKA designs that adopts a sagittally unconstrained lateral tibiofemoral articulation to allow more natural tibial rotation. This study was conducted to quantify motions in knees with this prosthesis to address two questions:

Does the medially conforming GMK Sphere design provide an AP-stable articulation that provides for tibiofemoral translations that are comparable to, but not larger than, translations measured in natural knees?

Does the medially conforming GMK Sphere design provide sufficient rotatory laxity to allow tibiofemoral rotations comparable to, but not larger than, rotations measured in natural knees?

Materials and Methods

Fifteen patients (9 females), mean age 65 years and mean BMI of 30 ±3, consented to participate. Sixteen knees received the GMK Sphere TKA. Mean Oxford Knee Score (OKS) improved significantly from 19±7 to 40±3 six months post surgery (P< 0.0001). On the day of the study, the mean OKS, Knee Society Score, EQ5D and Heath status scores were 40, 87, 0.83 and 85 respectively. Mean ROM from active maximum extension till maximum supine flexion was 108°±8°.

Motions in 16 knees were observed using pulsed-fluoroscopy during a range of activities. Subjects were observed in maximum flexion kneeling and lunging positions, and in stepping up/down on a 22cm step. Model-image registration methods were used to quantify three-dimensional knee motions from digitized fluoroscopic images.


Nicholas Dunbar Scott Banks

Tibial and femoral component malalignment is poorly tolerated in uni- and bi-compartmental knee replacement. Poor outcomes may still occur while using navigation or robotic-assisted bone preparation, which currently require surgeon assessment to establish a preoperative plan for implant placement. Choosing where to place partial knee replacement components is a challenging task that depends on complicated interactions between patient variability and implant design.

We developed a patient-customizable knee model that can assist surgeons by providing a quantitative measure of knee laxity. In order to build upon previous knee modeling efforts and to demonstrate the technique, three-dimensional femur and tibia bone and articular cartilage geometries were obtained from the OpenKnee finite element repository (https://simtk.org/home/openknee). Generic, patient-customizable transversely isotropic, fibril-reinforced cruciate and collateral ligament models, which allow for bone-to-ligament, cartilage-to-ligament, ligament-to-ligament interaction, were substituted into the model (Figure 1). This reduces the dependency on expensive and time-consuming MRI segmentation required to recreate soft-tissue geometries. Ligament pre-tensioning and insertion and origin sites (approximated as elliptical regions fit to the bone surface) can be tuned to match a patient's passive knee kinematics.

The model was run through a series of simulated passive flexion paths. At each degree of flexion, combinations of anterior-posterior and medial-lateral forces as well as internal-external and varus/valgus moments were applied and the resulting joint kinematics were recorded. These results represent the passive envelope of knee motion, which is used to characterize knee laxity. An optimization framework was developed to iteratively tune the cruciate ligament model to match a virtual set of passive loading conditions.

A majority of preoperative planning techniques only monitor geometric targets such as flexion and extension gaps, limb alignment, restoration of the joint line, and tibial component slope. Patient-customized knee models can be tuned to quantify post-operative knee laxity and identify the range of tolerable alignment of partial knee replacement components. Future work will employ in-vitro testing to validate the capability of the model to identify patient-specific cruciate ligament parameters.


Scott Banks

The history of knee mechanics studies and the evolution of knee arthroplasty design have been well reported through the last decade (e.g. [1],[2]). Through the early 2000's, there was near consensus on the dominant motions occurring in the healthy knee among much of the biomechanics and orthopaedic communities. However, the past decade has seen the application of improved measurement techniques to permit accurate measurement of natural knee motion during activities like walking and running. The results of these studies suggest healthy knee motion is more complex than previously thought, and therefore, design of suitable arthroplasty devices more difficult. The purpose of this paper is to briefly review the knee biomechanics literature before 2008, to present newer studies for walking and running, and to discuss the implications of these findings for the design of knee replacement implants that seek to replicate physiologic knee motions.

Many surgeons point to Brantigan and Voshell [3], an anatomic study of over one hundred specimens focusing on the ligamentous and passive stabilizers of the knee, as being an important influence in their thinking about normal knee function. M.A.R. Freeman and colleagues in London claim particular influence from this work, which motivated their extensive series of MR-based knee studies reported in 2000 [4,5,6]. These papers, perhaps more than any others, are responsible for the common impression that knee kinematics are well and simply described as having a ‘medial pivot’ pattern, where the medial condyle remains stationary on the tibial plateau while the lateral condyle translates posteriorly with knee flexion. Indeed, subsequent studies in healthy and arthritic knees during squatting and kneeling [7,8,9] and healthy and ACL-deficient knees during deep knee bends [10,11] show patterns of motion quite similar to those reported by Freeman and coworkers. These studies make a convincing case for how the healthy knee moves during squatting, kneeling and lunging activities. However, these studies are essentially silent on knee motions during ambulatory activities like walking, running and stair-climbing; activities which most agree are critically important to a high-function lifestyle.

In 2008 Koo and Andriacchi reported a motion laboratory study of walking in 46 young healthy individuals and found that the stance phase knee center of rotation was LATERAL in 100% of study participants [12]. One year later, Kozanek et al. published a bi-plane fluoroscopy study of healthy knees walking on a treadmill and corroborated the findings of Koo and Andriacchi, i.e. the center of rotation in healthy knees walking was lateral [13]. Isberg et al. published in 2011 a dynamic radiostereometric study of knee motions in healthy, ACL-deficient and ACL-reconstructed knees during a weight-bearing flexion-to-extension activity, and showed consistent anterior-to-posterior medial condylar translations with knee extension, accompanied by relatively little lateral condylar translation [14]. Hoshino and Tashman reported in 2012 another dynamic radiostereometric analysis of healthy knees during downhill running and concluded “While the location of the knee rotational axis may be dependent on the specific loading condition, during … walking and running … it is positioned primarily on the lateral side of the joint. ”[15] Finally, Claes et al. reported in late 2013 the detailed anatomy of the anterolateral ligament (ALL), another structure serving to stabilize the lateral knee compartment near extension, roughly in parallel with the anterior cruciate ligament (ACL) [16].

Studies since 2008 [9,12–16] show knee motions during walking, running and pivoting activities do not fit the “medial pivot” pattern of motion, but rather point to a “lateral pivot” pattern of knee motion consistent with the stabilizing roles of the ACL and ALL. Having a medial center of rotation in flexion and a lateral center of rotation in extension greatly complicates knee arthroplasty design if the goal is to reproduce kinematics approximating those observed in the natural knee. Consistent kinematics having a fixed center of rotation implies joint stabilizing structures or surfaces, not simply articular laxity allowing the knee to move as forces dictate. Thus, a total knee arthroplasty design seeking to reproduce physiologic motions may need to provide distinct means for controlling tibiofemoral motion in both extension and flexion. Recent studies of natural knee motions have made the implant designer's job more difficult!


Scott Banks Paris Flood

Model-image registration types of measurements have profoundly changed capabilities for studying dynamic 3D joint and implant kinematics since their introduction in the early 1990's. Since that time, a variety of proprietary and open-source software packages have been developed and reported for performing these measurements. Model-image registration based measurements have been used to quantify motions in natural and replaced knees, hips, ankles, shoulders, elbows, and spines in both single- and stereo-projection radiographic measurement setups. In theory, with the same quality images and the same quality bone/implant models, any of the software developed to perform model-image registration has the potential to provide equivalent measurement accuracy. Hence, much of the effort to improve measurement capabilities has been to reduce human interaction requirements and make the measurements more automatic and objective. In this paper, we report a new open-source software program that requires a minimum of user input to automate the 3D kinematic measurement process from single- or bi-plane radiographic projections.

JointTrack Auto (JTA) is an open source (sourforge.net/projects/jointtrackauto) program for performing model-image registration of metallic implants with single- or bi-plane radiographic images (see image). A predominantly edge-based cost function is used with an adaptive partioning global optimization scheme for model-image registration. Although this method works without any human intervention, JTA allows users to roughly identify one ‘feature’ of each implant that is visible in all images, e.g. the tip of a peg, to very significantly reduce the search space and time required for numerical optimization. This makes for a very convenient and fast initialization process where a human user simply mouse-clicks on a few easily identifiable locations in each radiographic image, and then the automated registration process is begun.

Registration accuracy examples and a software demonstration will be included in this e-poster presentation to introduce attendees to the software and spur discussion about the various methods available to perform these important measurements.


Akshdeep Bawa Harpal Singh Selhi

Introduction

Bilateral total knee replacement can either be simultaneous, in which both knees are operated in the same sitting, in one day, or staged, in which both knees are operated but not on the same day. With appropriate patient selection, the potential benefits of conducting this procedure in a simultaneous fashion outweigh the possible risks of the procedure. Very few studies have evaluated the results of bilateral knee replacement in a single sitting in Indian population.

Objectives

To determine the functional outcome after simultaneous knee replacement and assessment of the peri and post operative complications


Nicholas Beckmann Rudi Bitsch Joern Seeger Matthias Klotz Tobias Reiner J. Philippe Kretzer Sebastian Jaeger

Introduction

The frequency of revision hip arthroplasty is increasing with the increasing life expectancy and number of individuals treated with joint replacement. Newer porous implants have been introduced which may provide better treatment options for revision arthroplasty. These may require cementation to other prosthesis components and occasionally to bone, however, there is currently no information on how these porous implants interface with cement.

Materials and Methods

Cylindrical bone (control group) and porous metal probes with a diameter and height of 10mm were created and subsequently cemented in a standardized setting. These were placed under tensile and torsional loading scenarios.

In this experimental study, 10 human femoral heads were used to create 20 cylindrical probes with a diameter and height of 10mm. One side was tapered to 6mm for cementation and interface evaluation. A further set of 20 probes of a porous metal implant (Trabecular Metal®) was created with the same geometry. After the probes were created and lavaged, they were cemented at the tapered surface using a medium viscosity cement at a constant cementation pressure (1.2N/mm2). The setup allowed for comparison of the porous metal/cement interface (group A) with the well-studied control group interface bone/cement (group B).

The maximal interface stability of groups A and B were evaluated under tensile and rotational loading scenarios and the cement penetration was measured.


Francesco Maria Benazzo Loris Perticarini

Introduction

The project of a modular, double-conicity stem is born from the need to obtain primary stability and correct osseointegration in patients with developmental hip dysplasia, or proximal femoral dysmorphisms requiring a femoral shortening osteotomy or presenting characteristics of non-adaptability to single-conicity or straight stems. Such an implant could also be employed in femoral nail failures, or lateral femoral neck fractures requiring prosthetic substitution.

Aim of the study

To assess implantability of the new double-conicity stem in cadaver femurs, determining “fit and fill” and the behaviour of femoral cortical bone by means of Rx, CT and pre- and post-implantation mechanical testing.


Francesco Maria Benazzo Loris Perticarini

Between October 2001 and December 2010, 143 patients with developmental dysplasia underwent hip replacement surgery using a conical stem with modular necks (MODULUS) and titanium (Delta PF) and trabecular titanium cups system (Delta TT primary cups) (Lima Corporate, Villanova di San Daniele del Friuli, Italy), with ZTA/ZTA bearing (Ceramtec, Germany). 30 (21.0%) patients had both hips replaced, for a total of 173 implants. Mean age at the time of surgery was 55 years (range 22–81 years).

Dysplasia evaluation was based on the Crowe score (6): 66 (38.1%) hips were classified as 1, 50 (28.9%) as 2, 33 (19.1%) as 3 and 24 (13.9%) as 4.

Mean follow-up was 87 months (range 36–146 months); average Harris Hip Score increased from 42 (range 23–65) preoperatively to 92 (range 76–100) at the last follow-up. Stem revision was required in two cases. Cup revision was necessary in one case, for failed osteointegration.

A postero-lateral approach was used in all cases, with patients lying in a lateral decubitus position. Shortening femoral osteotomy was performed in 5 (2.9%) cases for implant reduction due to excessive tension: oblique osteotomy was employed in 3 cases, using the stem as a fixation device, while subtraction Z-osteotomy with two Dall-Miles cables was used in the other 2 cases. Supra-acetabular bone grafting was performed in 3 cases. In all cases, the cup was implanted at the level of the paleo-acetabulum or in the area between the paleo- and neo-acetabulum.

Head diameters were 28 mm in 54 (31.2%) cases, 32mm in 84 (48.6%) cases and 36mm in 35 (20.2%) cases.

The association of Modulus stem and Delta TT cups showed good long-term clinical and radiographic results, with a Kaplan-Meier survivorship of 98.8% at 12 years (95% CI, 97.1%-100%).


Sanaz Berahmani Dennis Janssen David Wolfson Maarten De Waal Malefijt Nico Verdonschot

A durable biological fixation between implant and bone depends largely on the micro-motions [Pilliar et al., 1986]. Finite element analysis (FEA) is a numerical tool to calculate micro-motions during physiological loading. However, micromotions can be simulated and calculated in various ways. Generally, only a single peak force of an activity is applied, but it is also possible to apply discretized loads occurring during a continuous activity, offering the opportunity to analyze incremental micro-motions as well. Moreover, micro-motions are affected by the initial press-fit. We therefore aimed to evaluate the effect of different loading conditions and calculation methods on the micro-motions of an uncemented femoral knee component, while varying the interference-fit.

We created an FE model of a distal femur based on calibrated CT-scans. A Sigma® Cruciate-Retaining Porocoat® (DePuy Synthes, Leeds, UK) was placed following the surgical instructions. A range of interference-fits (0–100 µm) was applied, while other contact parameters were kept unchanged. Micro-motions were calculated by tracking the projection of implant nodes onto the bone surface. We defined three different micro-motions measures: micro-motions between consecutive increments of a full loading cycle (incremental), micro-motions for each increment relative to the initial position (reference), and the largest distance between projected displacements, occurring during a discretized full cycle (resulting) (Fig. 1A). Four consecutive cycles of normal gait and squat movements were applied, in different configurations. In the first configuration, incremental tibiofemoral and patellofemoral contact forces were applied, which were derived from Orthoload database using inverse dynamics [Fitzpatrick et al., 2012]. Secondly, we applied the same loads without the patellofemoral force, which is often used in experimental set-ups. Finally, only the peak tibiofemoral force was applied, as a single loading instance. We calculated the average of micro-motions of all nodes per increment to compare different calculation techniques. The percentage of area with resulting micro-motions less than 5 µm was also calculated.

The percentage of surface area was increased non-linearly when the interference fit changed from 0 to 100 µm particularly for squat movement. Tracking nodes over multiple cycles showed implant migration with interference-fits lower than 30µm (Fig. 1A). Loading configurations without the patellofemoral force, and with only the peak tibiofemoral force slightly overestimated and underestimated the resulting micro-motions of squat movement, respectively; although, the effect was less obvious for the gait simulation when no patella force was applied. Both incremental and reference micro-motions underestimated the resulting micro-motions (Fig. 1B). Interestingly, the reference micro-motions followed the pattern of the tibiofemoral contact force (Fig. 1B).

The calculation technique has a substantial effect on the micro-motions, which means there is a room for interpretation of micro-motions analyses. This furthermore stresses the importance of validation of the predicted micro-motions against experimental set-ups. In addition, the minor effect of loading configurations indicates that a simplified loading condition using only the peak tibiofemoral force is suitable for experimental studies. From a clinical perspective, the migration pattern of femoral components implanted with a low interference fit stresses the role of an adequate surgical technique, to obtain a good initial stability.


Sanaz Berahmani Dennis Janssen David Wolfson Maarten De Waal Malefijt Nico Verdonschot

Femoral knee implants have promising outcomes, although some high-flex designs have shown rather high loosening rates (Han et al., 2007). In uncemented implants, it is vital to limit micromotions at the implant-bone interface, to facilitate secondary fixation through bone ingrowth (kienapfel et al., 1999). Hence, it is essential to investigate how micromotions of different uncemented implants are affected by various loading conditions when a range of bone qualities as a patient-related factor is applied.

Using finite element (FE) analysis, we simulated implant-bone interface micromotions during four consecutive cycles of normal gait and squat movements. An FE model of a distal femur was generated based on calibrated CT-scans, after which Sigma® and LCS® Cruciate-Retaining Porocoat® components (DePuy Synthes, Leeds, UK) were implanted. Using a frictional contact algorithm (µ=0.95), an initial press-fit fixation was simulated, which was previously validated against experimental data. The micromotions were calculated by tracking the projection of implant nodes on the bone surface excluding overhang area. The applied loading patterns were based on discretized simulations, providing incremental loads for each activity based on implant-specific kinematics, which was derived from Orthoload database using inverse dynamics (Fitzpatrick et al., 2012). This provided the opportunity to calculate incremental micromotions, but also the resulting micromotions for each single cycle, for both activities. In addition, the percentage of implant surface area with resulting micromotions less than a defined threshold was calculated.

Regardless of the type of loading, in all simulations, the predicted micromotions were highest in the first cycle, suggesting settling of the implant during initial cycle. The Sigma®implant displayed a 30% larger area with micromotions below the threshold of 5 microns, for both loading conditions (Fig. 1A). The highest micromotions occurred at the anterior flange, regardless of type of activity or design. Squatting had a more detrimental effect on the primary stability, with smaller areas of low micromotions as compared to the gait load (Fig. 1B). Bone stiffness had a minor effect, which was more apparent for squatting (Fig. 1B).

We found acceptable low ranges of micromotions in both implant designs, although demanding activities such as squatting generated higher motions. In addition, LCS® experienced higher micromotions, probably caused by the smaller contact area at bone-implant interface compared with Sigma®. Nevertheless, the predicted micromotions were all below the clinically relevant threshold for bone ingrowth (<40 microns) (kienapfel et al., 1999). Furthermore, our simulated settling behavior stresses the necessity for simulating multiple loading cycles, rather than just a single cycle. The effect of bone stiffness was evident, but only to a limited extent. The main current limitation of our study is the utilization of an elastic material model for the bone which is probably the reason to predict a low range of micromotions. We are planning to make the material model more realistic, by including plasticity and viscoelastic bone behavior.


Nicky Bertollo Michael Solomon William Walsh

Introduction

A thorough understanding of wear patterns and failure mechanisms of TKA components in the context of pre-revision knee kinematics is advantageous for component designers, manufacturers and surgeons alike. Traditional gait analysis provides an experimental technique to determine in vivo kinematics but is often limited by its cumbersome nature, infrastructure intensiveness and time. The recent introduction of the KneeKG (Emovi Inc, Canada) as a stand-alone knee motion tracking system which uses infrared technology provides a great opportunity to quickly, easily and routinely monitor patients at the clinical level, especially those being revised for component failure. This pilot study was conducted to examine pre-revision knee kinematics and subsequent wear patterns and failure mechanisms observed on the UHMWPE inserts upon retrieval in a cohort of TKA revision patients. We hypothesize that motion patterns can provide surgeons a unique insight into the status of the UHMWPE insert and implant longevity.

Methods

Patients requiring revision due to failure of the UHMWPE insert were recruited in this study after institutional ethical approval and written informed consent of the patients was obtained. Motion of the affected knee was quantified using a stand-alone infrared tracking system (KneeKG, Emovi Inc, Canada) whilst the patient was walking on a treadmill. All analyses were conducted within our institutional Physiotherapy Department. The KneeKG system is composed of passive motion sensors fixed on a validated knee harness, an infrared motion capture system (Polaris Spectra, Northern Digital Inc, USA) and a computer equipped with the Knee3D software suite (Emovi). Following application of the KneeKG trackers a calibration procedure was performed to identify joint centres and define a coordinate system on each body segment. After a treadmill habituation period of between 6 and 10 min, a trial was then conducted at the patient's comfortable treadmill gait speed over 45 sec. Averaged clinical rotations and translations of the tibia as a function of gait cycle were output by the system, and a report highlighting and detailing biomechanical deficiencies as compared to a database of normal controls automatically generated. Following the scheduled revision surgery the retrieved components were formalin-fixed and brought to our laboratory for a routine retrieval workup. All revisions were performed by a single surgeon. Components were analysed using optical and scanning electron microscopy techniques for regions of polishing, burnishing, pitting, delamination, deformation, scratching and embedded debris. Wear maps and scores were generated and correlated with pre-revision kinematics for each patient.


Hawar Akrawi Smail Abdessemed Manjit Bhamra

Introduction

The new era of shoulder arthroplasty is moving away from long stemmed, cemented humeral components to cementless, stemless and metaphyseal fixed implants and to humeral resurfacing. The early clinical results and functional outcome of stemless shoulder arthroplasty is presented.

Methods

A retrospective single-surgeon series of stemless shoulder prostheses implanted from 2011 to 2013 at our institution was evaluated. Perioperative complications, Theatre time and length of hospital stay (LOS) were recorded. Postoperative radiographic and clinical evaluation including measurement of joint mobility, the Oxford Shoulder Score (OSS), and Disabilities of the Arm, Shoulder and Hand (DASH) score by independent evaluators were made.


Carlo De Biase Marco Delcogliano Mario Borroni Domenico Marotta Giovanni Ziveri Gianni Pittalis Alessandro Castagna

Introduction

Reverse shoulder prosthesis has been developed to treat the clinical and pathological condition noted as cuff tear arthropathy (CTA).

The current models of reverse shoulder arthroplasty (RSA) expose the procedure to the risk of scapular notching, possibly leading to loosening of the glenoid.

Aim

The purpose of this study was to report updated results at a minimum follow-up of four years of 25 patients underwent reverse shoulder arthroplasty between 2006 and 2010 with an eccentric 36-mm glenoid component (SMR Lima).


Thom Bitter Dennis Janssen B. Willem Schreurs Tim Marriott Imran Khan Nico Verdonschot

Introduction

Recent reports implicate fretting corrosion at the head-stem taper junction as a potential cause of failure of some large diameter metal-on-metal (MOM) devices. Fretting observed at modular junctions is thought to be a type of ‘mechanically assisted’ corrosion phenomenon, initiated by mechanical factors that lead to an increase in contact stresses and micromotions at the taper interface. These may include: intra-operative taper assembly, taper contamination by debris or body fluids, patient weight and ‘toggling’ of the head or increased frictional torque in a poorly functioning bearing.

We adopted a finite element approach to model the head-taper junction, to analyze the contact mechanics at the taper interface. We investigated the effect of assembly force and angle on contact pressures and micromotions, during loads commonly used to test hip implants.

Materials and methods

Models of the Biomet Type-1 taper, a 60 mm head and a taper adaptor were created. These models were meshed with a mesh size based on a mesh density convergence study. Internal mesh coarsening was applied to reduce computational cost.

Elastic-plastic material properties based on tensile tests were assigned to all titanium components. The contact conditions used in the FE analyses were validated against push-on and pull-off experiments, resulting in a coefficient of friction of 0.5.

To analyze micromotions at the taper-adaptor connection, the models were loaded with 2300N (ISO 7206-4) and 5340N (ISO 7206-6), after being assembled with 2-4-15 kN, axially and under a 30º angle. This ISO standard is commonly used to determine endurance properties of stemmed femoral components.

Micromotions and contact pressures were analyzed by scoring them to an average micromotion and average contact pressure for the surface area in contact.


Michael Conditt Thomas Coon Alvaro Hernandez Sharon Branch

INTRODUCTION

Bicompartmental knee arthroplasty (BKA) is an alternative to total knee arthroplasty (TKA) for degenerative joint disease when present in only two compartments. BKA spares the cruciate ligaments and preserves bone in the healthy compartment, possibly leading to better knee kinematics and clinical outcomes when compared to TKA. While BKA is a technically demanding procedure when performed with manual instrumentation, robotic assistance allows for accurate implant placement and soft tissue balancing of the joint. Robotic unicompartmental knee arthroplasty (UKA) has shown favorable clinical outcomes and survivorship at short term (2 year) follow up compared to manual UKA. The purpose of this study is to evaluate the short term functional outcomes and survivorship of patients undergoing robotically assisted BKA.

METHODS

45 patients (48 knees) were identified in an initial and consecutive single surgeon series receiving robotically assisted BKA to correct disease in the medial and patellofemoral compartments. As part of an IRB approved study, every patient in the series was contacted at a minimum two year (±2 months) follow up and asked a series of questions to determine implant survivorship and functional outcomes (using the patient portion of the Knee Society Score). 9 patients were lost to follow up and 1 patient was deceased. 35 patients (38 knees) at a minimum two year follow up enrolled in the study for an enrollment rate of 79%. There are 22 male patients and 13 female patients; the average age at time of surgery is 67.0 ± 6.8 and the average BMI is 29.5 ± 4.6. Five patients in this series also qualified for a 5 year follow up assessment.


Todd Borus Don Roberts Pamela Fairchild Jennifer Christopher Michael Conditt Sharon Branch Jonathan Matthews Kyle Pirtle Michael Baer

Introduction

Unicompartmental Knee Arthroplasty (UKA) has been offered as a tissue sparing alternative to total knee arthroplasty (TKA) for treatment of early to mid-stage osteoarthritis (OA). While the spared tissue and retention of cruciate ligaments may result in faster recovery, smaller incision, less bone resection, decreased pain and blood loss and more normal kinematics and function, UKA has shown unpredictable results in practice, which may be due to variations in surgical techniques1. Recently a robotic-assisted technique has been introduced as a means to provide more consistent and reproducible surgical results. In this study, the early return to function was measured to determine proposed benefits between UKA and TKA.

Methods

Patients requiring either UKA or TKA were prospectively enrolled in this IRB approved study. Each patient received pre-operative education regarding their expected physical therapy (PT) regimen, which was uniform for all patients. PT was determined to be concluded when each patient reached an achievable functional endpoint with each of the following 5 criteria: range of motion from 5 to 115 degrees, recovery of flexion and extension strength to 4/5 of pre-operative strength, gait with minimal limp and without an assistive device for 250 feet and ability to ascend and descend a flight of stairs with step over gait and good control. The number of PT visits to reach each functional goal was recorded.


George Branovacki Daniel Yong Thomas Prokop Michael Redondo

Purpose

Traditional total knee arthoplasty techniques have involved implantation of diaphyseal stems to aid in fixation expecially when using constrained polyethylene inserts. While the debate over cemented vs uncemented stems continues, the actual use of stems is considered routine. The authors' experience with cemented stemmed knee revisions in older patients with osteoporotic bone has been favorable. Our younger patients with press-fit stems from varying manufacturers have been plagued with a relatively high incidence of component loosening and stem tip pain in the tibia and occasionally thigh. We report the early results of the first 20 total knee revisions using press-fit metaphyseal filling sleeved stemless implants with constrained bearings.

Methods

Twenty three patients with failed primary or revision total knees were assigned to receive stemless sleeved revision knee designs using the DePuy MBT/TC3 system. Reasons for revision included loosening, implant fracture, stiffness, instability, and stem pain. Twenty patients (ages ranging from 42–73) were successfully reconstructed without stems. Six knees with significant uncontained cavitary defects were included. Three patients with unexpectedly osteoporotic metaphyseal bone were revised with cemented stemmed implants and excluded. All cases used cement for initial fixation on the cut bone surface and fully constrained mobile bearing inserts.


Gregory Brown

Significance

In spite of evidence that total knee replacement (TKR) surgery is effective, numerous studies have demonstrated that approximately 20 percent of patients who have undergone TKR surgery are not satisfied. This relatively high rate of patients who are not satisfied is the result of unmet patient expectations. The strongest predictor of dissatisfaction after TKR is unmet expectations (RR = 10.7, Bourne, Chesworth, et al, 2010). This is confirmed by Dunbar, Richardson, and Robertsson (2013): “Unmet expectation seems to be a major cause of unsatisfactory outcomes and satisfaction is most strongly correlated with relief of pain, followed by improvement in physical function.” Hypothesis: One year post-operative pain relief and activity level expectations can be measured pre-operatively and used for shared decision making.

Methods

A web–based system for prospectively collecting patient reported outcomes (PROs) has been developed. The data set for total hip/knee replacement surgery includes: (1) European quality of life, EQ-5D; Oxford Hip Score/Oxford Knee Score; (3) Lower Extremity Activity Scale (LEAS); and (4) Pain Likert Scale (PLS). The EQ-5D was selected as the health related quality of life (HRQL) general outcome measure because it has been adopted by multiple international joint replacement registries (Swedish Hip Arthroplasty Register, Norwegian Arthroplasty Register, United Kingdom National Joint Registry). The EQ-5D can be used to calculate quality adjusted life years (QALYs) for economic and/or comparative effectiveness analyses. The OHS/OKS questionnaires are used by the United Kingdom National Joint Registry and the New Zealand Joint Registry. The LEAS and PLS are used to measure patient's expectations for pain relief and functional improvement by asking patients to report their pre-operative pain and activity level before surgery and asking patients to report their pain and activity level expectations one year after surgery.


Gregory Brown

Significance

In ideal shared decision making (SDM), evidence-based treatment options, their likelihood of success, and the probability of adverse events is discussed with the patient. However, current SDM is fundamentally flawed because evidence for patient-specific treatment effectiveness and patient-specific adverse event risks is lacking. Observational outcome registries are better than randomized clinical trials for determining patient prognostic factors for outcomes and adverse events. No orthopaedic SDM clinical tools exist to predict patient-specific outcomes. Hypothesis: A patient-specific shared decision making tool can predict clinically significant outcomes and adverse events for total knee replacement (TKR) surgery.

Methods

A web–based prospective observational outcome registry collects patient reported outcomes (PROs) for TKR surgery. The data set for TKR surgery includes: (1) European quality of life (EQ-5D); (2) Oxford Knee Score (OKS); (3) Lower Extremity Activity Scale (LEAS); and (4) Pain Likert Scale (PLS). A TKR outcome calculator predicts patient-specific functional outcome with a regression model using patient-specific pre-operative Oxford Knee Scores, diagnosis, co-morbidities, and demographics. Patient-specific joint infection relative risk is calculated using diagnosis, co-morbidities, and demographics. Functional outcomes are presented as minimum clinically important differences (MCIDs). MCID=σΔ/2.


Martin Browne David Barrett Adonis Balabanis Christopher Rowland

Increased incidence of obesity and longer life expectancies will place increased demands on load bearing joints. In the present work, a method of pre-clinical evaluation to assess the condition of the joint and potentially inform on cases of joint deterioration, is described. Acoustic emission (AE) is a non-destructive test methodology that has been used extensively in engineering for condition monitoring of machinery and structures. It is a passive technique that uses piezoelectric sensors to detect energy released from internal structural defects as they deform and grow. The technique has been used with some success in the past to identify characteristic signals generated from the knee joint during activities such as standing and sitting, in candidate arthroplasty patients (1,2). In this study, 40 asymptomatic subjects had AE data generated from their knee joints analysed. Subject characteristics such as age, gender, and lifestyle were disclosed and evaluated against the AE data.

Each subject was invited to take a seated position and a piezoelectric AE sensor (Pancom P15, 150kHz resonance, 19mm diameter) was attached to the subject's knee using a wax couplant and tape as close to the articulating surface and on a bony prominence to avoid signal attenuation in the soft tissue.

Subjects were invited to sit and stand 3 times. AE data were collected and processed using an AMSY5 AE processor (Vallen, Germany). Tests were repeated on a separate occasion and selected subjects were invited to participate on a third occasion. The AE data of particular interest were the peak amplitudes and the frequency power spectrum of the waveform.

Post-test inspection of subject characteristics allowed them to be separated into three broad categories: no previous history (group A), some instances of pain in the knee (group B), and those who have had previous minor surgery on the knee (group C). The corresponding AE results were grouped separately. It was found that groups A and B demonstrated similar signal amplitude characteristics while group C produced much higher, significantly different (p<0.05) amplitudes and amplitude distributions. Typical results are shown in figure 1.

At present, broad trends could be identified and relationships emerged between the data and subject history (prior surgery, typical daily activity). Further work will continue with asymptomatic subjects and the work will be extended to pre-operative patients to identify whether certain trends are amplified in this population.


Danilo Bruni Michele Gagliardi Tedi Marko Giovanni Raspugli Ibrahim Akkawi Maurilio Marcacci

PURPOSE

Lateral osteoarthritis of the valgus knee is a challenging problem, especially for young and active patients, where prosthetic replacement is not indicated. The purpose of the present study is to evaluate clinically and radiographically 91 patients with valgus knee treated with distal femoral varus osteotomy in mid and long term follow-up.

METHODS

A clinical retrospective evaluation based on IKDC, OXFORD and WOMAC scores of 91 patients at 4 to 10 years of follow-up was performed. Subjective evaluation was based on a VAS for pain self-assessment. Radiographic evaluation was performed by an independent observer of all 91 patients at 2 to 6 years of follow-up. A survival analysis was performed assuming revision for any reason as primary endpoint.


Danilo Bruni Tedi Marko Michele Gagliardi Simone Bignozzi Stefano Zaffagnini Ibrahim Akkawi Francesca Colle Maurilio Marcacci

Introduction

The purpose of this study was to examine whether three types of mobile-bearing PCL sacrificing TKA could restore the native knee translation and rotation. The primary hypothesis was that there are differences in knee kinematics and laxity between three different cruciate-substituting TKA designs: 1 with post-cam mechanism, 2 post-cam mechanism based on an inter-condylar ‘third condyle’ concept, 3 anterior stabilized with deep-dished highly congruent tibial insert; specifically, showing different femoral external rotation with flexion, different femoral translation with flexion and different laxity under stress test. The secondary hypothesis was that there is different clinical outcome between the three TKA designs at 2 years follow-up.

Methods

We recruited 3 cohorts consisting of 30 patients each divided according 3 different TKA designs. All patients were operated with navigated procedure. During surgery preoperative and postoperative kinematics were recorded, in terms of femoral antero-posterior translation and tibial rotation during knee flexion, as also preoperative and postoperative at 2 years follow-up clinical scores have been acquired.


Danilo Bruni Michele Gagliardi Alberto Grassi Giovanni Raspugli Ibrahim Akkawi Tedi Marko Maurilio Marcacci

BACKGROUND

Some papers recently reported conflicting results on implant survivorship in all-poly tibial UKRs. Furthermore, the influence of BMI on this specific implant survivorship remains unclear, since existing reports are often based on small series of non-consecutive patients with different follow up durations, enabling to generate meaningful conclusions.

PURPOSE

To determine the 10-years survival rate of an all-poly tibial UKR in a large series of consecutive patients and to investigate whether a correlation exists between a higher BMI and an increased risk of revision for any reason.


Danilo Bruni Laura Bragonzoni Michele Gagliardi Marco Bontempi Tedi Marko Sivio Patella Maurilio Marcacci

Background

Roentgen Stereophotogrammetric Analysis (RSA) represents nowadays an excellent solution for high-accuracy fixation measurement of UKAs. To date, to the best of our knowledge, no previous study has investigated long-term micromotions of a UKA using RSA. For this reason, the main purpose of the present study is to determine long-term implant fixation of 15 UKAs with all-poly tibial component using RSA at a mean 10-years follow-up. The secondary purpose was to investigate whether the progressive loss of implant's fixation correlates with a reduction of KSS scores.

Methods

Fifteen non-consecutive patients with primary knee osteoarthritis received a UKA with an all-poly tibial component between January 1995 and April 2003 in the Authors' institution. Pre and post-operative KSS scores were recorded. RSA evaluation was performed on day 2 after surgery, than at 3, 6, and 12 months and yearly thereafter. The patients were evaluated with a mean follow-up of 10 years.


Tony Bryant Christopher Stevens Brett Bentley Kevin Farmrer Thomas Wright

Background

Glenoid component aseptic loosening is the most common source of total shoulder arthroplasty (TSA) revision. In an attempt to strengthen cemented glenoid component fixation, divergent pegged glenoids were designed. Divergent peg creation was intended to increase cement purchase and provide resistance to component rocking.

Methods

Thirty-four patients who underwent divergent peg TSA had data collected prospectively. The data from these patients was retrospectively reviewed, primarily for radiographic evidence of glenoid component loosening. The endpoint was defined as the need for revision secondary to glenoid loosening. Secondary outcome measures such as SPADI (shoulder pain and disability index), active forward elevation, abduction, internal rotation, and external rotation were also collected. Data was obtained preoperatively and at the following postoperative intervals: 3 months, 6 months, and yearly. The last available postoperative radiographs were also reviewed and graded on a modified Franklin glenoid lucency scale described by Lazarus et al.


Matthew P. Abdel Sebastien Parratte Nicolaas Cyrillus Budhiparama

Whether to resurface the patella during a primary Total Knee Replacement (TKR) performed as a treatment of degenerative osteoarthritis remain a controversial issue. Patellar resurfacing was introduced because early implants were not designed to accommodate the native patella in an anatomic fashion during the range of motion. Complications related to patella resurfacing became a primary concern and have been associated with the variable revision rates often report post TKR. Subsequent modifications in implant design have been made to offer the surgeon option of leaving the patella un-resurfaced.

Numerous clinical trials have been done to determine the superiority of each option. Unfortunately, there is little consensus and surgeon preference remains the primary variable. One of the major reasons given to support patella resurfacing is to eliminate Anterior Knee Pain post operatively. However, studies have shown that this problem was not exclusively found in non-resurfaced patients so the author conclude that anterior knee pain is probably related to component design or to the details of the surgical technique, such as component rotation rather that whether or not the patella is resurfaced.

An increasing rate of complications with the extensor mechanism after patellar resurfacing led to the concept of selective resurfacing of the patella in TKR. Decision making algorithms with basis of clinical, radiographic and intraoperative parameters have been developed to determine which patients are suitable for patella resurfacing and which are suitable for patella non-resurfacing.

Finally, the continued study of this topic with longer follow up term in randomized, controlled, clinical trials remains essential in our understanding of patella in TKR. The development of joint registry will allow surgeons to draw conclusions on the basis of larger numbers of patients and will improve the reporting of the results of patellar non resurfacing in clinical trials. In general, surgeons in United States always resurface while their counterparts in Europe tend to never resurface.


Nicolaas Cyrillus Budhiparama Christopher S Mow Rob Nelissen

Computer navigation has been introduced as an adjunct to Total Knee Arthroplasty (TKA) to assure precision positioning, accurate bone resection and optimal component alignment. Using Computer Assisted Navigation in TKA was a hotly debated issue in United States and elsewhere. Although Computer Navigation has progressed from the 1st generation to the current 3rd generation system, there are still no clearly tangible, apparent long term clinical benefits.

There is some evidence that using Computer Assisted Surgery may lower the incidence of malalignment of mechanical limb axis compared to conventional component placement methods, but it is unclear whether this marginal benefit will translate to concrete positive long term outcomes. AAHKS survey results indicated that the majority of Orthopedic Surgeons were not using computer navigated surgical techniques. The implementation of CAS met with so many hurdles and obstacles because its approach consumes more time and a long learning curve, which translates to added cost and complexity. It is also labor and equipment intensive but only increases accuracy in the “right” hands. Lack of popularity for CAS has induced the innovation of Patient Specific Jigs which has been proven to be extremely accurate, efficient with respect to time and allows surgeons to navigate the operation prior to the procedure.

Since CAS remains unpopular in the US, it would be even less popular in Asia for the obvious reasons of high cost, lack of experts to handle technical difficulties, lack of publicity, and the paucity of beneficial expert testimonies. The “Better, Cheaper, Faster” culture is fully ingrained in the minds of most Asian Arthroplasty surgeons and CAS would seem to only fulfill the “Better”, but not the “Cheaper and Faster” expectations in most hands.


Sophia Burns J. Agustin Soler Giulio Cuffolo Amit Sharma Yeggapan Kalairajah

Introduction

Acetabular revision for cavitary defects in failed total hip replacement remains a challenge for the orthopaedic surgeon. Bone graft with cemented or uncemented revision is the primary solution; however, there are cases where structural defects are too large. Cup cage constructs have been successful in treating these defects but they do have their problems with early loosening and metalwork failure.

Recently, highly porous cups that incorporate metal augments have been developed to achieve greater intra-operative stability showing encouraging results.

Methods

Retrospective analysis of twenty-six consecutive acetabular revisions with Trabecular Titanium cups. Inclusion criteria included aseptic cases, adult patients, end-stage disease with signs of loosening, no trauma nor peri-prosthetic fractures.

Data was obtained for patient demographics, Paprosky classification, use of bone graft, use of acetabular augment, and Moore index of osseointegration.


Giorgio Calori Massimiliano Colombo Emilio Mazza Simone Mazzola Emiliano Malagoli

Introduction

The development of new megaprosthesis for the treatment of large bone defects has offered important opportunities to orthopedic oncologic surgeons for the replacement of skeletal segments such as the long bones of the upper and lower limbs and the relative joints. Our experience, treating non union and severe bone loss, has brought us, sometimes, to be confronted with the reality of some failures after unsuccessful attempts to reconstruct. Faced with certain radiological and / or clinical drastic situations we wanted to apply the principles of Biological Chamber and oncologic surgery with megaprosthetic replacement solutions. We implanted megaprosthesis with either 1 step or 2 steps (previous antibiotated spacer) technique depending on the septic patient conditions. The aim of this study is to retrospectively evaluate both clinical and radiological outcomes in patients underwented to a lower limb megaprosthesis implant and complications were recorded.

Materials and Methods

In total, we treated 58 patients with megaprosthesis mono-and bi-articular subdivided as follows: proximal femur, distal femur, proximal tibia and total femur. The mean follow-up of patients is about 24 months (5 yrs max, min 6 months) with clinical and serial radiographic revaluations with standard methods (X-ray in 45 days, 3–6-12-18-24 months) as well as monitoring of blood parameters of inflammation for at least 2 months


Giorgio Calori Massimiliano Colombo Simone Mazzola Emiliano Malagoli

INTRODUCTION

The hip arthroplasty implant is currently growing up both in orthopedic and trauma practice. This increases the frequency of prosthesis revision due to implant loosening often associated with periprosthetic osteolysis that determine the failure and lead to a loss of bone substance.

Nowadays there are numerous biotechnologies seeking to join or substitute the autologous or omologous bone use. These biotechnologies (mesenchymal stromal cells, growth factors and bone substitutes) may be used in such situations, however, the literature doesn't offer class 1 clinical evidences in this field of application.

MATERIALS AND METHODS

We performed a literature review using the universally validated search engines in the biomedical field: PubMed / Medline, Google Scholar, Scopus, EMBASE. The keywords used were: “Growth Factors”, “Platelet Rich Plasma”, “OP-1”, “BMP”, “BMP-2”, “BMP-7”, “Demineralized Bone Matrix”, “Stem Cell”, “Bone Marrow”, “Scaffold”, “Bone Substitutes” were crossed with “hip”, “revision”, “replacement” / “arthroplasty”, “bone loss” / “osteolysis.”


Gianluca Camillieri Vittorio Calvisi

Self-locking button-like fixation devices for ACL reconstruction are attracting knee surgeons' attention due to promising technical advantages: complete filling of the tunnel with graft, anatomic reconstruction (AM portal), fixation achievement even when a short tunnel is reamed, opportunity of graft re-tensioning after tibial fixation and/or cyclic load. We compared two similar devices (TightRope vs ToggleLocZL)

20 fresh-frozen porcine femurs (mean age 2.1 years) were assigned to the two groups by randomization. Hamstrings with 9 mm of diameter were obtained using bovine tendons that show the same biomechanic behaviour of human hamstrings. Femoral tunnel was created by AM portal technique (anatomic position). Zwick-Roell z010 tension/compression device with bone and tendon clamps, was used for the study:

Cyclic test (1000 cycles, 0.5 Hz, 50–250 N/cycle, 50 cycles of preload at 10–80 N/cycle)

Final pull-out test (1 mm/s)

Failure analysis

CT scan and densitometry

Any implant didn't fail during cyclic test. The elongation average was 2.85±1.63 for ToggleLoc and 2.71±.85 for TightRope (P>0.05). Pull-out test showed different values in terms of Ultimate Strength Failure (USF), Stiffness at USF, and Stiffness:

The failure mode was:

The mean method of failure was the fracture of the cortical bone of the femoral condyle, for both groups. But if we extrapolate the USF the difference was favourable(P<0.05) for TightRope (707.83 N) than ToggleLoc (580.16).

The mean bone density of porcine femora was comparable to young human femora (1.12±0.31 BMD)

The reproducibility of surgical technique, the mechanical strength and endurance of the systems suggest two valid options for ACL reconstruction with hamstring. ToggleLoc showed worse results due to the sharp squared edges of the button.


Gianluca Camillieri Mariano Di Salvatore Annalisa Mancò

Transverse pin femoral fixation of bone-patella tendon-bone (BPTB) in ACL reconstruction has been widely applied during the last decades. Aim of our study is to confront two different system of transverse femoral fixation for BPTB graft: Transfix BTB (Arthrex) and BioTransfix T3 (Arthrex). The main differences between these two system are the diameter (3.0 mm Transfix BTB and 3.5 mm BioTransfix T3), and section (Transfix BTB is cannulated). Surgical technique adopts the same transverse vectorial guide but different guide sleeves.

30 fresh-frozen porcine knees (mean age 2.2 years) were assigned to the two groups randomisedly. the patellar bone block and tendon were harvested using the same size in all specimens (10mm × 25 mm, 10 mm). Zwick-Roell z010 tension/compression device with bone clamps, was used for the study:

Cyclic test (1000 cycles, 0.5 Hz, 50–250 N/cycle, 100 cycles of preload)

Final pull-out test (1 mm/s)

Failure analysis

CT scan and densitometry

Any implant didn't fail during cyclic test. The elongation average was 1.85±0.63 for Transfix BTB and 1.69±0.87 for BioTransfix T3. Pull-out test showed very similar values in terms of Ultimate Strength Failure (USF), Stiffness at USF, and Stiffness:

The failure mode was bone plug fracture (12 for Transfix BTB and 13 for BioTransfix T3) and tendon failure (3 for Transfix BTB and 2 for BioTransfix T3).

The post-test CT scan showed any failure of the fixation devices and the correct position inside the femoral half-tunnel.

The mean bone density of porcine femora was comparable to young human femora (1.12±0.31 BMD)

Both systems showed a similar behaviour in terms of USF, Stiffness, Cyclic load, method of failure and other biomechanical parameters. The reproducibility of surgical technique, the mechanical strength and endurance of the systems suggest two valid options for ACL reconstruction with BPTB even if in-vivo studies are necessary to confirm the animal ex-vivo biomechanical data.


Ornusa Chalayon Richard Tyler Epperson Roy Bloebaum Nicole Abdo

Introduction

Fixation has been shown to be the primary indicator of an implant's long-term success. Failure to achieve attachment, especially in acetabular and TKR, has been attributed to a lack of initial stability and gaps between the implant and bone. Gaps greater than 150 microns allow fibrous tissue to form. Properly addressing implant design features can help avoid adverse outcomes.

ASTM International Standards (F1854-09) do not assess the relationship between porosity of the coating and that of cancellous bone, which can lead to an absence of mechanical interlock. This study developed a virtual program that uses human cancellous bone to predict potential skeletal attachment for implants properly placed for TJR. The goal of the Virtual Paradigm was to assess initial contact surface area at the time of implantation.

Methods

Seven human femurs and tibias were used. Bones from 11 males and 3 females were used, ages ranging from 40 to 61. Five porous coatings were assessed: Biofoam (Wright Medical), Fiber Mesh, CSTI, Tantalum (Zimmer), and P² (DJO Global).


Chyun-Yu Yang Chih-Wei Chang Yen-Nien Chen Chih-Han Chang

Introduction

Total knee arthroplasty [TKA] is a common procedure to relieve painful disability from advanced knee arthritis. However, related blood loss, ranging from 800 to 1200 ml, increase risk and disruption of recovery in anemic patients following TKA. Various methods for blood conservation had been proposed and examined. In the literature, the intra-articular administration of a solution mixing bupivacaine and epinephrine was commonly used after knee surgeries. Therefore, we conducted a retrospective, case controlled review of our primary TKAs to determine the hemostatic efficacy of this regimen following TKAs.

Material and Methods

Over a period of 12 months, 135 eligible patients were divided two groups simply according to the intra-articular injection or not: a control group (N=63) and a treatment group (N=72). In the treatment group, a 40 ml vial of 0.5% bupivacaine with epinephrine 1: 200000 was given prior to the deflation of pneumatic tourniquet. No drainage was used in all TKAs. Without recordable drainage, a Gross formula, considering gender and body composition, was used for estimate blood loss following TKAs. In addition, serial changes in hemoglobin as well as the requirement of allogenic transfusion were also compared between groups.


Yuhan Chang

Background

Fungal infection at an arthroplasty site is rare and poses a therapeutic challenge. To the best of our knowledge, no reports have been published thus far on the success rate of prosthesis reimplantation after fungal prosthetic joint infections.

Questions/purposes

We asked: (1) What is the success rate in terms of infection eradication using a two-stage exchange arthroplasty in patients with hip or knee fungal periprosthetic joint infections, particularly focusing on Candida infections? (2) What patient-, infection-, and treatment-related variables are associated with the success or failure of treatment?


Yuhan Chang

Objectives

This study is to compare the elution characteristics, antimicrobial activity, and mechanical properties of antibiotic-loaded bone cement (ALBC) loaded with powder antibiotic, powder antibiotic with inert filler (xylitol), or liquid antibiotic, particularly focusing on vancomycin and amphotericin B.

Methods

Cement specimens loaded with 2 g of vancomycin or amphotericin B powder (powder group), 2 g of antibiotic powder, and 2 g of xylitol (xylitol group) or 12 ml of antibiotic solution containing 2 g of antibiotic (liquid group) were tested.


Dickson Chau Yee Sze Teo Lau Cheng Kiang Jerry Chen Ing How Moo

Introduction

Standard image-free navigation systems have proven to improve the accuracy of components placement and reduce the proportion of outliers for lower limb mechanical axis in total knee arthroplasty (TKA). However, their disadvantages include a longer duration of surgery and pin-tract related complications. More recently, pinless navigation has been developed to address these shortcomings. This study aims to investigate the effectiveness of a new pinless navigation system (Zimmer® iAssist™ Knee) in TKA.

Methods

Power analysis was performed. To detect a significant difference in the proportion of outliers for lower limb mechanical axis at a power of 0.80, a sample size of 50 patients would be required. Between May 2013 and April 2014, 50 patients diagnosed with osteoarthritis of the knee were divided into two surgical technique arms: 1) iAssist™; 2) conventional TKA. One Adult Reconstruction surgeon performed all the surgeries. The patients were prospectively followed up and postoperative long leg radiographs were taken at one month post-surgery. Two reviewers blinded to the surgical method performed the measurements on radiographic films. Five radiographic measurements were measured: 1) Hip-Knee-Ankle Angle (HKA); 2) Coronal Femoral-Component Angle (CFA); 3) Coronal Tibia-Component Angle (CTA); 4) Sagittal Femoral-Component Angle (SFA); and 5) Sagittal Tibia-Component Angle (STA), The Mann-Whitney U test was used to compare the two groups for quantitative variables while the Fisher's exact test was used for categorical variables.


Yen-Nien Chen Chih-Wei Chang Hung-Chih Chang Chih-Han Chang Yi Lin

Cannulated screw is commonly used in the fixation of proximal femoral neck fractures. In the literature, several configurations had been proposed for best mechanical support with clinical experiences or biomechanical tests. Although screws in triangle configuration contribute certain fixation stability, but sometimes the surgeons made their own choices have to conduct another fixation pattern for some factors such as fracture type, economic issues, and so on. Therefore the aim of this study is to analyze the mechanical responses of a fractured femur fixed with screws in different configurations, screw materials and screw diameters with finite element method, trying to find the most stable construct.

A solid femur model was built from the CT images of a standard saw bone. Three fracture types of the femoral neck were created according to Pauwel's classification (30?, 50?, 70?) by CAD software. The models of implanted screws were built according to a commercial cannulated screw (Stryker Osteosynthesis, Schoenkirchen/Kiel, Germany) with diameter 6.5mm and 4.5mm by CAD software, too. Three fixation configurations were analyzed in this study, including triangle with superior single screw with titanium diameter 6.5mm, triangle with inferior single screw with diameter 6.5mm and diamond with four stainless screw diameter 4.5mm (fig.1). Totally there were nine models constructed in this study, and all of them were then imported into ANSYS WORKBENCH v14 (Swanson Analysis, Houston, PA, USA) to mesh and further analysis. 700N vertical downward force was applied on the femur head and the distal end of femur shaft was totally fixed.

The triangle fixation with superior single screw resulted in a best stability, but the fracture fixed with screws in a diamond configuration has least fracture gap. The difference of the maximum displacement of the femur head with Pauwel's classification 70?between triangle fixation with superior single screw and diamond configuration is only 0.03mm (1.72–1.69 mm). In most unstable femoral neck fracture [Pauwel's classification 70], the maximum gap distance is 0.59mm under the diamond configuration, while it is 0.63mm as the fracture fixed with a triangle configuration.

Therefore, this study suggests that four 4.5mm stainless screws in a diamond configuration is an alternative for proximal femur fracture once 6.5mm titanium screws are not available.


Junji Chiba Harry E Rubash

The Magna ROM 21 knee prosthesis was designed in 1994 to match the anatomical characteristics of the Japanese knee and achieve deep knee flexion to suit Japanese lifestyles. The prosthesis has a smaller anteroposterior mediolateral diameter ratio for the femur and tibia than do knees designed in the United States. The purpose of this study was to review the clinical results of the first 159 arthroplasties performed with this prosthesis in order to asses whether this cementless implant had achieved its design objectives. 159 knees were followed for 12.6 to 14.0 years (mean, 13.4 years). Preoperatively the mean The Knee Society knee score and function score were 24.9 and 27.5 points; postoperatively they were 94.6 and 83.8 points. The mean preoperative and postoperative ranges were 106 and 118 degrees, respectively. Total knee arthroplasty with the Magna ROM 21 resulted in an excellent range of motion and a high level of satisfaction wth the operation.


Neil Duplantier David Briski Mark S. Meyer J. Lockwood Ochsner George Chimento

Background

Hospitalists have assumed an evolving role in the care of postsurgical orthopaedic patients. Literature has provided evidence to suggest improved outcomes in postsurgical hip fracture patients managed by hospitalists in nonteaching hospitals. However, the full impact of a hospitalist co-management model has not been fully investigated with regard to elective joint arthroplasty patients in a multispecialty teaching facility. We hypothesized that a hospitalist co-management model in the setting of a teaching hospital would lead to an increase in unnecessary medical workups for joint arthroplasty patients.

Methods

We retrospectively evaluated 2231 patients who underwent total hip arthroplasty (THA) or total knee arthroplasty (TKA) between May 2010 and January 2014 at one teaching facility, excluding any non-elective trauma patients. The patients were separated into a non-hospitalist (NH) cohort of 1062 patients that did not receive hospitalist co-management postsurgery, and a hospitalist (H) cohort of 1169 patients that received hospitalist co-management postsurgery. We used Student t test and significance of (P<0.05) to compare the following factors between the two patient cohorts: length of stay (LOS), readmission rates at 30 and 90 days postsurgery, number of diagnoses present on admission, and number of new diagnosis given during admission. We then compared the average number of diagnostic and laboratory studies performed per patient and the average cost per hospital stay between the two cohorts.


Bradford Waddell Talal Zahoor Mark S. Meyer J. Lockwood Ochsner George Chimento

Introduction

Tranexamic acid (TXA) has been shown to decrease hemoglobin loss and reduce the need for transfusions in primary hip and knee arthroplasty. Recently, authors have proven similar results in revision total knee arthroplasty (TKA). No previous paper has focused on the safety and efficacy of TXA for revision TKA for periprosthetic joint infection (PJI). The purpose of our study was to evaluate the safety and efficacy of topical TXA in revision TKA for PJI.

Methods

We performed a retrospective review of all patients who underwent two-stage revision total knee arthroplasty for infection at our institution between September 25, 2007 and July 12, 2013. We evaluated hemoglobin loss, need for transfusion, one-year reinfection rate, length of stay (LOS), complications and one-year mortality with and without the use of TXA in all patients who underwent Stage-1 removal of hardware with antibiotic spacer placement and/or revision (Stage-2) for PJI of the knee. All data sets were analyzed using a two-sample t-test.


Yoon Je Cho Dong Hur Young Soo Chun Kee Hyung Rhyu

Purpose

Cementless cup with structural allograft is one of option for acetabular revision in the cases which has severe bone loss. This study was performed to verify that the structural allograft with cementless cup could be one of good options for revision of acetabular cup with severe bone defect and to verify that the allograft resorption affect the stability of cementless acetabular cup.

Materials and Methods

We reviewed 25 cases of 25 patients who underwent acetabular cup rvision using cementless porous coated hemispherical cup with structural allograft from May 1992 to July 2011 July 2011. There were nine males and sixteen females with an average age of 50.0 years. The average follow-up period was 76.7(28∼212) months. The clinical evaluation was performed using Harris Hip Score(HHS) and UCLA activity score. Radiologically, the degree of resorption of grafted bone, incorporation of allograft bone with normal bone, osteolysis and cup loosening were evaluated.


Sung-Do Cho Yoon-Seok Youm Jong-Hyun Kim

Purpose

To evaluate the effectiveness of post-operative pain management using the intra-operative peri-articular injection(PAI) and/or electromyography (EMG)-guided preoperative femoral nerve block (FNB) in total knee arthroplasty(TKA).

Materials and Methods

From March 2013 to February 2014, 90 knees which underwent primary TKA by one surgeon were included in our study. The patients were classified into three groups; a single injection FNB with an EMG guide (Group I, 30 knees), intra-operative PAI (Group II, 30 knees) and both FNB and PAI (Group III, 30 knees). Pain at rest and moving was evaluated by Visual Analogue Scale (VAS) at postoperative 0, 4, 8, 24 and 48 hours. Postoperative range of motion, time to walking, total blood loss, amount of opioid consumption and complications were compared in each group.


Woo-Shin Cho

Introduction

The bone defect reconstruction is the first step of successful primary or revision TKA in case of large bone defect. If the defect is not reconstructed adequately, we can neither preserve knee joint function nor guarantee long survival of the implant. Allogeneic bone graft is known to be the treatment of choice in large defect. However the surgical technique is demanding and incorporation failure is constant issue of the allogeneic bone graft. We propose new bone defect reconstruction technique using multiple screws and cement.

Material and method

From April 2012 to April 2014, 12 patients with large defect which could not be reconstructed with metal augment were involved in this study. The bone defect type was 10 cases of 2A and 2 cases of 2B according to AORI (Anderson Orthopedic Research Institute) classification. The defect was reconstructed with multiple screws and cementing technique by single surgeon (WS Cho). Average follow-up period was 15 months. (24 ∼ 1 month)


Sung-Do Cho Yoon-Seok Youm Jong-Hyun Kim

Purpose

The NexGen® legacy posterior stabilized (LPS)-Flex total knee system (Zimmer, Warsaw, IN) is designed to provide 150° of flexion following total knee arthroplasty (TKA). But, recent reports found a high incidence of loosening of the femoral component related to the deep flexion provided. We evaluated 9- to 12-year clinical and radiological follow-up results after NexGen® LPS-Flex TKA.

Materials and Methods

A retrospective evaluation was undertaken of 209 knees in 160 patients (21 males, 139 females) who were followed up for more than 9 years after Nexgen®LPS-Flex TKA. Evaluations included preoperative and postoperative range of motion(ROM), Knee Society(KS) knee score, function scores, tibiofemoral angle and assessment of postoperative complications.


Changhee Cho Teruo Murakami Yoshinori Sawae

Ultra-high molecular weight polyethylene (UHMWPE) is the sole polymeric material currently used for weight-bearing surfaces in total joint arthroplasty. However, the wear phenomenon of UHMWPE components in knee and hip prostheses after total joint arthroplasty is one of the major restriction factors on the longevity of these implants. In order to minimize the wear of UHMWPE and to improve the longevity of artificial joints, it is necessary to clarify the factors influencing the wear mechanism of UHMWPE. In the microscopic surface observation of the virgin knee prosthesis with anatomical design, various grades of microscopic surface scratches and defects caused by machining and surface finishing processes during manufacture of the component were observed on the surface of the metallic femoral component [Fig. 1] (C. Cho et al, 2009), although the overall surface were finished at smoother level. It is thought that certain levels of the microscopic surface asperities caused by these surface damages in the metallic femoral component might contribute to increasing and/or accelerating wear of the UHMWPE tibial insert. Therefore, it is necessary to clarify quantitatively the influence of the microscopic surface asperities of the metallic components in virgin artificial joints on the wear of UHMWPE components.

The primary purpose of this study was to investigate the influence of the microscopic surface asperities of the virgin metallic femoral component on the wear of the UHMWPE tibial insert in the virgin knee prosthesis. In this study, the authors focused on the three-dimensional shape of the microscopic surface asperities as a factor influencing the wear mechanism of the UHMWPE tibial insert. The 3D microscopic surface profile measurement of the virgin metallic femoral component using a laser microscope and reproduction of the femoral component surface using 3D CAD software were performed [Fig. 2] in order to produce idealized 3D finite element models of the microscopic surface asperity of the femoral component based on actual measurement data. Elasto-plastic finite element contact analyses between idealized microscopic surface asperities and UHMWPE were also performed in order to investigate the influence of the three-dimensional shape of the microscopic surface asperities of the virgin metallic femoral component on the wear of the UHMWPE tibial insert. The analytical findings of this study suggest that the aspect ratio and shape ratio [Fig. 3] of the microscopic surface asperity of the virgin metallic femoral component have an important influence on increasing and/or accelerating wear of the UHMWPE tibial insert.


Choong Hyeok Choi Kyu Sung Chung Jin Kyu Lee Hee Jae Lee

Introduction

The purpose of this study was to evaluate the mid-term clinical and radiological results in patients who were managed by double metal augmentations in proximal tibial uncontained bony defects undergoing primary or revision total knee arthroplasty

Materials and Methods

We performed double metal augmentations in proximal tibial uncontained bony defects undergoing total knee arthroplasty. Out of total 14 patients, 8 patients (4 priamry arthroplasty, 4 revision arthroplasty), mean 61.3 (50–80) years, were available for review at least 5 years follow up. The average follow up period was 86.3(60–99) months. Range of motion, American Knee Society Score were evaluated pre- and postoperatively as a clinical values. Another clinical assessments undertaken at the final reviews, Western Ontario and McMaster Universities osteoarthritis index (WOMAC), Oxford knee score (OKS), Short Form-36 (SF-36), Lower extremity functional scale (LEFS), and Lower extremity activity scale (LEAS) were checked. Radiological results, involving presence of radiolucent lines (RLLs) > 1mm in width, and osteolysis at the block-cement-bone interface were taken under fluoroscopic images at postoperatively and annually thereafter.


Choong Hyeok Choi Kyu Sung Chung Jin Kyu Lee Tae Yang Shin

Introduction

We investigated the incidence of venous thromboembolism (VTE) and pulmonary embolism (PE) after total knee arthroplasty (TKA) and assessed the efficacy and complications of three different chemical prophylactic regimens.

Materials and Methods

From May, 2011 to November 2013, 268 patients, 330 knees were randomly allocated to three groups, low molecular weight heparin (LMWH) 5000IU for 2 days followed by aspirin 100mg for 5 days (Group HA, 110 knees), rivaroxaban 10mg for 7 days (Group X7, 110 knees), or for 10 days (Group X10, 110 knees) postoperatively. Intermittent pneumatic compression device was applied on all patients. The multidetector row computed tomography (MDCT) was done at postoperative 10 days to evaluate VTE (PE & DVT separately), and MDCT was rechecked to evaluate the changes of VTE at postoperative 3 months in VTE patients. Additionally, major and minor bleeding complications, amounts of bleeding, and bruise around wound were checked.


Thanainit Chotanaphuti Saradej Khuangsirikul Nathaphol Nuansalee

Osteolysis is one of a major cause of failure that affect long term survival rate in THA. Hard-on-hard bearing surface were developed to reduce wear and osteolysis, such as ceramic-on-ceramic which is the lowest wear rate was introduced but it still has squeaking and ceramic fracture. Metal-on-metal bearing surface significantly reduce wear rate but it still release metal ion which affect local tissue reaction. Then ceramic-on-metal is another choice of bearing with combine the advantage of reduce wear rate, metal ion release, no stripe wear, no squeaking and no ceramic fracture. However after clinical use ALTRs may occur and disturb the longevity of THA.

During January 2009 to December 2009 we performed 98 THR with the same femoral stem and acetabular cup with difference bearing which were 87 cases of metal on cross-linked PE, 8 cases of ceramic on metal and 5 cases of metal on metal. Routinely postoperative care were done with clinical evaluation, plain x-rays and Harris hip score. After 5 years follow up there are clinical problems in ceramic on metal THA with decrease clinical score and progressive osteolysis in radiographic finding in 2 cases then we investigated to find the cause of this problem and revise the components. We preformed magnetic resonance imaging and collect blood sample for ESR, CRP and Cobalt and Chromium level. We revised 2 cases of ceramic on metal THA, during surgery we collected tissue for bacterial and AFB and histopathology. All retrieval components were studied for wear pattern. First patient have thigh pain and progressive osteolysis after year 4th of follow up. She had normal ESR and CRP with high level of cobalt and chromium level. We revised both components and tissue histopathology showed metallosis with chronic inflammation. Another patient had failure due to ALTRs with mixed solid-cystic mass at trochanteric bursa but component is stable then only bearing surface were change. Wear pattern at femoral head was in weight bearing area with corresponding to apical center wear of metal liner.

Our study showed that only in group of ceramic-on-metal THA that have 5 years follow up have early reoperation due to osteolysis and tissue reaction. We routinely stop to use this bearing since 2010. But we have small number of cases in our study to conclude that is bearing are not suitable for clinical usage.


Thanainit Chotanaphuti

Purpose

Correct sizing of prostheses is a considerable factor regarding function and successful rate of total knee arthroplasty (TKA). Patient-specific guide (PSG), using CT preoperative planning for sizing, alignment and bone cutting, has been developed to improve the accuracy and reproducibility of TKA. The purpose of this study is comparing the accuracy of CT-based preoperative sizing in PSG with the conventional femoral sizing instrument.

Methods

From January 2012 to December 2012, fifty-four patients underwent TKA with CT-based PSG. Preoperative sizing was compared to the component size measured intra-operatively by conventional anterior reference femoral sizing instrument. The actual sizes of implanted components were also recorded to analyze the accuracy of each measurement.


Suzanne Goh Kenon Chua Desmond Chong Andy Yew Ngai Nung Lo

Introduction

Total hip replacement is an established surgical procedure done to alleviate hip pain due to joint diseases. However, this procedure is avoided in yonger patients with higher functional demands due to the potential for early failure. An ideal prosthesis will have have a high endurance against impact loading, with minimal micromotion at the bone cement interface, and a reduced risk of fatigue failure, with a favourable stress distribution pattern in the femur. We study the effect of varying the material properties and design element in a standard cemented total hip using Finite Element Analysis.

Methods

A patient-specific 3D model of femur will be constructed from CT scan data, while a Summit® Cemented Hip System (DePuy Orthopedic) will be used to as a control for comparative evaluation. We vary the material stiffness of different parts of the prosthesis(see Fig.1) to formulate a design concept for a new total hip prosthesis design; and use Finite Element Method to predict the micromotion of the hip prosthesis at the bone cement interface, as well as the stress distribution in the the femur.


Ian Clarke Giuseppe Pezzotti Alan Lakshminarayanan Michelle Burgett-Moreno Thomas Donaldson

Introduction

Looking for optimal solutions to wear risks evident in total hip arthroplasty (THA), silicon nitride ceramic bearings (Si3N4) are noted for demanding high-temperature applications such as diesel engines and aerospace bearings. As high-strength ceramic for orthopedic applications, Si3N4 offers improved fracture toughness and fracture strength over contemporary aluminas (Al2O3). Our pilot studies of Si3N4 in 28mm diameter THA showed promising results at ISTA meeting of 2007.1 In this simulator study, we compared the wear resistance of 40mm to 28mm diameter Si3N4 bearings.

The 28mm and 40mm bearings (Fig. 1) were fabricated from Si3N4 powder (Amedica Inc, Salt Lake City, UT).1 Wear tests run were run at 3kN peak load in an orbital hip simulator (SWM, Monrovia, CA) and. The lubricant was standard bovine serum (Hyclone: diluted to 17 mg/ml protein concentration). Wear was measured by gravimetric method and wear-rates calculated by linear regression. SEM and interferometic microscopic was performed at 3.5-million cycles (3.5Mc) to 12Mc.

The simulator was run to 3.5Mc duration with no consistent weight-loss trends. The bearings could show either small positive or negative weight fluctuations in an unpredictable manner (Fig. 2). Surface analysis showed protein layers up to 3μm thick, furrowed due to abrasion by small particles (Fig. 3). The low ceramic wear was camouflaged by protein contaminants alternatively forming and shedding. From 3.5 to 12.8Mc duration we experimented with various detergents and wash-procedures, all to no avail. Protein coatings were also more prevalent on 44 mm heads, likely due to frictional heating by the larger diameter effect. Selected heads were washed with a mild acid solution - the cumulative effect appeared to be removal of some protein layers, but not in a predictable manner.

The Si3N4 ceramic is used in demanding industrial applications and it is therefore unfortunate that we are yet not able to quantify the actual wear performance of Si3N4/ Si3N4 bearings (COC). The contaminating protein layers combined with low-wearing silicon nitride obscured the actual wear data. This has also been a problem in prior studies with alumina and zirconia bearings. Considerable challenges still stand in the way of the optimal biomaterials choices that will result in reduced risk of failure while providing extended lifetimes. Thus important issues remain unsolved and call for innovative solutions. Searching for a more effective ‘wear-measurement’ remedy, we noted that abrasive slurries of bone cement (PMMA) used in contemporary simulator studies were effective in promoting adverse wear in polyethylene bearings. These investigations also revealed that PMMA debris did not damage CoCr heads2,3, alumina heads4,5 or diffusion-hardened zirconia heads (ZrDH).6 We can therefore speculate at this ISTA meeting of 2014 that future ceramic wear tests should incorporate PMMA slurries. Here a new hypothesis can be formulated, that PMMA particulates will provide a continual and beneficial removal of contaminating proteins from the ceramic surfaces (see Fig. 3) and thereby aid definition of low-wearing COC bearings such as Si3N4.

The application of non-oxide ceramics such as silicon nitride presented here may become a viable alternative for THA designs of next decade.


Ian Clarke Dan Sufficool John G Bowsher Christina Savisaar Michelle Burgett-Moreno Thomas Donaldson

Introduction

Hip simulators proved to be valuable, pre-clinical tests for assessing wear. Preferred implant positioning has been with cup mounted above head, i.e. ‘Anatomical’ (Figs. 1a-c) 1,2 while the ‘Inverted’ test (cup below head) was typically preferred in debris studies (Figs. 1d-f).3,4 In an Anatomical study, wear patterns on cups and heads averaged 442 and 1668 mm² area, respectively, representing 8% and 30% of available hemi-surface (Table 1), i.e. the head pattern was ×3.8 times larger than cup. This concept of wear patterns is illustrated well in the ‘pin-on-disk’ test (Fig. 1) in which the oscillating pin has the ‘contained’ wear area (CWP) and the large wear track on the disk is the ‘distributed’ pattern (DWP). Hip simulators also create CWP and DWP patterns, site dependant on whether Anatomical (Fig. 1a-c) or ‘Inverted’ (Fig. 1d-f) test. However there is scant foundation as to clinical merits of either test mode. Retrieval studies of MOM bearings have indicated that cups have the larger wear patterns, i.e. contrary to simulator tests running Anatomical cups (Table 1).5 Therefore we compared Anatomical and Inverted cup modes using 38mm and 40mm MOM in two 5-million cycle simulator studies.

Methods

38mm and 40mm MOM bearings were run in Anatomical mode (study-1) and Inverted (study-2) mode, respectively, in a hip simulator. Lubricant was bovine serum diluted to provide protein concentration 17 mg/ml. Wear was measured gravimetrically and wear-rates calculated by linear regression. Wear patterns were assessed by stereomicroscopy and compared to algorithms using standard spherical equations.


Ian Clarke Thomas Halim Michelle Burgett-Moreno Joseph Thompson John Vinciguerra Thomas Donaldson

Introduction

Over 40-years the dominant form of implant fixation has been bone cement (PMMA). However the presence of circulating PMMA debris represents a 3rd-body wear mechanism for metal-on-polyethylene (MPE). Wear studies using PMMA slurries represent tests of clinical relevance (Table 1). Cup designs now use many varieties of highly-crosslinked polyethylene (HXPE) of improved wear resistance. However there appears to be no adverse wear studies of vitamin-E blended cups.1–4 The addition of vitamin E as an anti-oxidant is the currently preferred method to preserve mechanical properties and ageing resistance of HXPE. Therefore the present study examined the response of vitamin-E blended liners to PMMA abrasion combined with CoCr and ceramic heads. The hip simulator wear study was run in two phases to compare wear with, (i) clean lubricants and (ii) PMMA slurries.

Methods

The vitamin-e blended polyethylene liners (HXe+) were provided by DJO Surgical (Austin, TX) with 40mm CoCr and ceramic femoral heads (Biolox-delta). Polyethylene liners were run in standard “Inverted” test. (Table 1) All cups were run in ‘clean’ serum lubricant for 6-million load cycles (6Mc)5 and in a debris slurry (PMMA: 5mg/ml concentration) for 2Mc.4 A commercial bone cement powder was used as “abrasive” (Biomet, Warsaw, IN). PMMA slurries were added at test intervals 6, 6.5, 7 and 7.5Mc.4 Wear was assessed gravimetrically and characterized by linear regression. Bearing roughness was analyzed by interferometry and SEM.


Justin Cobb Ruaraigh Collins Victoria Manning Michela Zannotto Emily Moore Gareth Jones

The Oxford Hip Score (OHS), the Harris Hip Score (HHS) and WOMAC are examples of patient reported outcome measures (PROMs) have well documented ceiling effects, with many patients clustered close to full marks following arthroplasty. Any arthroplasty that offers superior function would therefore fail to be detectable using these metrics. Two recent well conducted randomised clinical trials made exactly this error, by using OHS and WOMAC to detect a differences in outcome between hip resurfacing and hip arthroplasty despite published data already showing in single arm studies that these two procedures score close to full marks using both PROMS.

We had observed that patients with hip resurfacing arthroplasty (HRA) were able to walk faster and with more normal stride length than patients with well performing hip replacements, but that these objective differences in gait were not captured by PROMs. In an attempt to capture these differences, we developed a patient centred outcome measure (PCOM) using a method developed by Philip Noble's group. This allows patients to select the functions that matter to them personally against which the success of their own operation will be measured.

Our null hypothesis was that this PCOM would be no more successful than the OHS in discriminating between types of hip arthroplasty.

22 patients with a well performing Hip Resurfacing Arthroplasty were identified. These were closely matched by age, sex, BMI, height, preop diagnosis with 22 patients with a well performing conventional THA. Both were compared with healthy controls using the novel PCOM and in a gait lab.

Results

PROMs for the two groups were similar, while HRA scored higher in the PCOM. The 9% difference was significant (p<0.05).

At top walking speed, HRA were 10% faster, with a 9% longer stride length.

Discussion

Outcome measures should be able to detect differences that are clinically relevant to patients and their surgeons. The currently used hip scores are not capable of delivering this distinction, and assume that most hip replacements are effectively perfect. While the function of hip replacements is indeed very good, with satisfaction rates high, objective measures of function are essential for innovators who are trying to deliver improved functional outcome.

The 9% difference in PCOM found in this small study reflects the higher activity levels reported by many, and of similar magnitude to the 10% difference in top walking speed, despite no detectable difference in conventional PROMS. PCOMs may offer further insight into differences in function. For investigators who wish to develop improvements to hip arthroplasty, PCOMs and objective measures of gait may describe differences that matter more to patients than conventional hip scores.


Justin Cobb Simon Harris Milad Masjedi

Large heads offer substantial advantages over small ones in hip arthroplasty, as they are far less likely to dislocate. This feature is of particular benefit in very dysplastic females who often have a degree of joint laxity making dislocation a real possibility. Large metal heads have a range of problems, so registries report that they are now being substituted by large ceramic heads, typically reducing in diameter by 15% or more from the native size.

All current designs of the femoral ball heads, whether for resurfacing of replacement share a unique design characteristic: a subtended angle of 120° defining the proportion of a sphere that the head represents. A novel design has recently been proposed that might reduce conflict between the femoral ball head rim and the iliopsoas tendon. This paper explains the problem of iliopsoas impingement on femoral heads of native diameter, and the consequences.

Material and Methods

Using MRI, we measured the contact area of the Iliopsoas tendon on the femoral head in sagittal reconstruction of 20 hips with symptoms of FAI. We also measured the Articular extent of the femoral head on 40 normal hips and 10 dysplastic hips. We then performed virtual hip resurfacing on normal and dysplastic type hips, attempting to avoid the overhang of the rim inferomedially.

Results

The contact area of the Iliopsoas tendon on the femoral head in extension is well visualized (Figure 1). The femoral head articular surface has a subtended angle of 120° anteriorly and posteriorly, but only of 100° medially. Virtual surgery in a femoral head of a dysplastic hip showed that when the femoral head is resurfaced with an anatomic sized component, the femoral ball head has a 20° skirt of metal protruding medially where iliopsoas articulates (figure 2). Reducing this by 15%, (eg to put a 40mm ball head onto a hip that had a 46mm femoral diameter), completely avoids any chance of iliopsoas tendon using the femoral head as a fulcrum. MRI of a dysplastic hip with a 40mm ball shows that iliopsoas impingement is hard to substantiate (figure 3).


Justin Cobb Justin Boey Victoria Manning Anatole Wiik

Introduction

Our primary hypothesis was simple: does gait on a downhill gradient distinguish between types of knee arthroplasty? Our secondary hypotheses were these: are stride length and other kinematic variables affected by cruciate ligament integrity following knee arthroplasty?

Participants

Ethical approval was sought and gained prior to commencement of the study. 52 subjects were tested on the instrumented treadmill, 3 groups (UKA, TKA, and young healthy control) of 19, 14, and 19 respectively. The two high performing arthroplasty groups were recruited from a database of patient related outcome measures (PROMs) and were chosen based on high Oxford knee scores (OKS) with a minimum 12 months post hip arthroplasty.


Francesca Colle Nicola Lopomo Danilo Bruni Michele Gagliardi Tedi Marko Francesco Iacono Stefano Zaffagnini Maurilio Marcacci

Introduction

Providing proper rotational alignment of femoral component in total knee arthroplasty is mandatory to achieve correct kinematics, good ligament balance and proper patellar tracking. Recently functional references, like the function flexion axis (FFA), have been introduced to achieve this goal. Several studies reported the benefits of using the FFA but highlighted that further analyses are required to better verify the FFA applicability to the general clinical practice. Starting from the hypothesis that the FFA can thoroughly describe knee kinematics but that the joint kinematics itself can be different from flexion to extension movements, the purpose of this study was to analyse which factors could affect the FFA estimation by separately focusing on flexion and extension movements.

Methods

Anatomical acquisitions and passive joint kinematics were acquired on 79 patients undergoing total knee arthroplasty using a commercial navigation system. Knee functional axis was estimated, from three flexion and extension movements separately acquired included in a range between 0° and 120°. For flexion and extension, in both pre- and post-implant conditions, internal-external (IE) rotations was analysed to track any changes in kinematic pattern, whereas differences in FFA estimation were identified by analysing the angle between the FFA itself and the transepicondylar axis (TEA) in axial and frontal plane.


Francesca Colle Nicola Lopomo Danilo Bruni Michele Capozzi Stefano Zaffagnini Maurilio Marcacci

Introduction

The use of a surgical navigation system has been demonstrated to allow to intraoperatively analyze knee kinematics during total knee arthroplasty (TKA), thus providing the surgeon with a quantitative and reproducible estimation of the knee functional behaviour. Recently severak authors used the computer assisted surgery (CAS) for kinematic evaluations during TKA, in particular to evaluate the achievement of a correct joint biomechanics after the prosthesis implantation. The major concern related to CAS is that the movements are usually passively performed, thence without a real active task performed by the subject. Starting from the hypothesis that the passive kinematics may properly describe the biomechanic behaviour of the knee, the main goal of this work was to intra-operatively compare the active kinematics of the limb, analysing a flexion movement actively performed by the patient, and the passive kinematics, manually performed by the surgeon.

Methods

The anatomical and kinematic acquisitions were performed on 31 patients TKA using a commercial navigation system (BLU-IGS, Orthokey, USA). All the surgeries were performed under local anesthesia, which specifically allowed to acquire the passive and active kinematics including three flexion movements. Both in pre- and post-implant conditions, internal-external (IE) rotations and anterior-posterior (AP) translations were estimated to track any changes in the kinematic pattern.


Francesca Colle Nicola Lopomo Danilo Bruni Francesco Iacono Stefano Zaffagnini Maurilio Marcacci

Introduction

Several methods, based on both functional and anatomical references, have been studied to reach the goal of a proper knee kinematics in total knee arthroplasty (TKA). However, at present, there is still a large debate about which is the most precise and accurate method to achieve the correct rotational implant positioning. One of the main methods already used in TKA to describe the tibiofemoral flexion-extension movement, based on a kinematic technique, thus not influenced by the typical variability related to the identification of anatomical references, is called “functional flexion axis” (FFA) method. The purpose of this study was to determine the repeatability in estimating knee functional flexion axis, thus evaluating the robustness of the method for navigated total knee arthroplasty.

Methods

Passive kinematic and anatomical acquisitions were performed with a commercial navigation system on 87 patients undergoing TKA with primary osteoarthritis. Knee FFA was estimated, before and after implant positioning, from three flexion-extension movements between 0° and 120° (Figure 1). The angle between Functional Flexion Axis and an arbitrary clinical reference, the transepicondylar axis (TEA), was analysed in frontal and axial view (Figure 2). Repeatability Coefficient and Intraclass Correlation Coefficient (ICC) were estimated to analyse the reliability and the agreement in identifying the axis.


Benjamin Domb John Redmond Jon Hammarstedt Alexandra Petrakos Christine Stake Asheesh Gupta Michael Conditt

Background

Several recent reports have documented high frequency of malpositioned acetabular components, even amongst high volume arthroplasty surgeons. Robotic assisted total hip arthroplasty (THA) has the potential to improve component positioning; however, to our knowledge there are no reports examining the learning curve during the adoption of robotic assisted THA.

Purpose

The purpose of this study was to examine the learning curve of robotic assisted THA as measured by component position, operative time, intra-operative technical problems, and complications.


Benjamin Domb John Redmond Asheesh Gupta Jon Hammarstedt Alexandra Petrakos Christine Stake Michael Conditt

Background

Component positioning in total hip arthroplasty (THA) is critical to achieve optimal patient outcomes. Recent literature has shown acetabular component positioning may be inaccurate using traditional techniques. Robotic-assisted THA is a recent platform introduced to decrease the risk of malpositioned components. However, to date, a paucity of data is available comparing the intra-operative component position generated by the navigation system to post-operative radiographs.

Purpose

The purpose of this study was to compare the component position measurements of a navigation system, used during robotic-assisted THA, to component position measurements obtained on post-operative radiographs.


Michael Conditt Giorgio Franceschi Davide Bertolini Claudio Khabbazè Augusto Rovini Roberto Nardaccione

Introduction

Isolated lateral compartment osteoarthritis (OA) occurs in 5–10% of knees with OA [1, 2]. Lateral unicompartmental knee arthroplasty (LUKA) emerged as a treatment to this disease in the early 80s but challenging surgical technique has limited the prevalence of this treatment option [1–3]. A robotic-arm assisted surgical technique (MAKO Surgical Corp.) has emerged as a way to achieve precise implant positioning which can potentially improve surgical outcomes.

Objectives

The purpose of this study was to evaluate short term outcomes for patients that received LUKA using a novel robotic-arm assisted surgical technique.


Michael Conditt Thomas Coon Martin Roche Frederick Buechel Todd Borus Jon Dounchis Andrew Pearle

Introduction

High BMI has been classically regarded as a contraindication for unicompartmental knee arthroplasty (UKA) as it can potentially lead to poor clinical outcomes and a higher risk of failure. In recent years, UKA has increased in popularity and, as a result, patient selection criteria are beginning to broaden. However, UKA performed manually continues to be technically challenging and surgical technique errors may result in suboptimal implant positioning. UKA performed with robotic assistance has been shown to improve component positioning, overall limb alignment, and ligament balancing, resulting in overall improved clinical outcomes. The purpose of this study is to examine the effect of high BMI in patients receiving UKA with robotic assistance.

Methods

1007 patients (1135 knees) were identified in an initial and consecutive multi-surgeon multi-center series receiving robotically assisted medial UKA, with a fixed bearing metal backed onlay tibial component. As part of an IRB approved study, every patient in the series was contacted at a minimum two year (±2 months) follow up and asked a series of questions to determine implant survivorship and satisfaction. 160 patients were lost to follow up, 35 patients declined to participate, and 15 patients were deceased. 797 patients (909 knees) at a minimum two year follow up enrolled in the study for an enrollment rate of 80%. 45% of the patients were female. The average age at time of surgery was 69.0 ± 9.5 (range: 39–93). BMI data was available for 887 knees; the average BMI at time of surgery was 29.4 ± 4.9. Patients were stratified in to five categories based on their BMI: normal (< 25; 16%), overweight (25–30; 46%), obese class I (30–35; 25%), obese class II (35–40; 11%) and obese class III (>40; 2%).


Raelene Cowie Silvia Carbone Sean Aiken John Cooper John Fisher Louise Jennings

Introduction

When third body particles originating from bone cement or bone void fillers become trapped between articulating surfaces of joint replacements, contact surfaces may be damaged leading to accelerated wear and premature failure of the implant. In this study, the damage to cobalt chrome counterfaces by third body particles from PMMA bone cement (GMV, DePuy) and various bone void fillers was investigated; then wear tests of UHMWPE were carried out against these surfaces.

Methods

Third body particles of polymerised GMV bone cement and the bone void fillers; OsteoSet (with tobramycin), Stimulan and Stimulan+ (with vancomycin and tobramycin) (provided by Biocomposites Ltd.) were trapped between an UHMWPE pin and a highly polished cobalt chrome plate. A load of 120N was applied to the pin and using an Instron materials testing machine, the plate was pulled beneath the pin to recreate third body damage [1]. The resulting surface topography of the plate was analysed using white light interferometry (Bruker NPFLEX). Pin on plate wear tests of GUR 1020 UHMWPE pins were carried out against the plates perpendicular to the direction of damage for 500,000 cycles in 25% bovine serum using a 6-station multi-axial reciprocating rig under conditions to replicate the kinematics in total knee replacement. Wear of the pins was determined by gravimetric analysis and results were compared to negative (highly polished) control plates and positive controls scratched with a diamond stylus (lip height 2µm). Statistical analysis was carried out using one-way ANOVA with significance taken at p<0.05.


Raelene Cowie Adam Briscoe John Fisher Louise Jennings

Introduction

UHMWPE articulating against PEEK-OPTIMA® has the potential for use as a novel bearing couple in joint arthroplasty due to its potentially low wear rates and the bioinertness of its wear debris. The aim of this study was to investigate the role of protein in the lubricant on the wear of UHMWPE articulating against PEEK at both room and physiological temperature.

Methods

The wear of GUR1020 UHMWPE pins articulating against PEEK plates (Ra ∼0.06µm) was compared to highly polished cobalt chrome plates (Ra <0.01µm) in a 6-station multi-axial pin-on-plate rig using kinematics to replicate those in total knee arthroplasty. Tests were carried out at either ∼20°C or ∼36°C and wear was investigated under varying concentrations of bovine serum (0, 25 or 90%). Studies were carried out for 1 Million cycles with wear of the UHMWPE pins assessed gravimetrically using unloaded soak controls to compensate for moisture uptake.

Statistical analysis was carried out using ANOVA with significance taken at p<0.05.


Emilie Crosnier Duncan Scrivens Patrick S Keogh Anthony Miles

Introduction

The hip joint is subjected to cyclic loading during activities of daily living and this can induce micromotion at the bone-implant interfaces of uncemented implants. Osseointegration, which is essential for long term implant survival, will occur when micromotion at these interfaces is below 40µm and may occur up to 150µm [1].

Studies investigating the micromotion of press-fit acetabular cups only report micromotions in one direction. Standard methods also maintain a static cup position throughout testing; usually at the angle of maximum resultant force during gait. Current methods therefore do not take into account the effect of motion of the hip on micromotion of the cup, nor do they investigate all six degree of freedom (DoF) of motion.

The aim of this study was to assess press-fit cup micromotion in six DoF under physiological loading when the cup is held statically and moved in flexion-extension.

Methods

A cementless acetabular cup (Trident, Stryker) was implanted into polyurethane foam blocks (Sawbones, density = 0.48g/cm³) with a 1mm press-fit. The blocks were manufactured to replicate important anatomical features, which model the acetabulum (Figure 1). A six DoF measurement system was rigidly attached to the bottom of the cup through the dome screw hole and micromotion was measured using six LVDT sensors (Figure 2).

The micromotion of the cup was measured under three conditions. Firstly, the cup was tested statically at 30° flexion, representing heel strike during gait; secondly, under dynamic motion simulating gait (30° flexion to −15° extension; 0.5Hz); and finally, under dynamic motion simulating stair climb (45° flexion to −15° extension; 0.5Hz) [2]. For all conditions, the cup was cyclically loaded to a peak load of 2.0kN for 1000 cycles at 1Hz. The loading cycles were synchronised with the flexion-extension movement in order to achieve a loading peak at both heel strike and toe-off positions.


Darryl D'Lima Jonathan Netter Jerry D'Alessio Mark Kester Clifford Colwell

Background

Wear and fatigue damage to polyethylene components remain major factors leading to complications after total knee and unicompartmental arthroplasty. A number of wear simulations have been reported using mechanical test equipment as well as computer models. Computational models of knee wear have generally not replicated experimental wear under diverse conditions. This is partly because of the complexity of quantifying the effect of cross-shear at the articular interface and partly because the results of pin-on-disk experiments cannot be extrapolated to total knee arthroplasty wear. Our premise is that diverse experimental knee wear simulation studies are needed to generate validated computational models. We combined five experimental wear simulation studies to develop and validate a finite-element model that accurately predicted polyethylene wear in high and low crosslinked polyethylene, mobile and fixed bearing, and unicompartmental (UKA) and tricompartmental knee arthroplasty (TKA).

Methods

Low crosslinked polyethylene (PE). A finite element analysis (FEA) of two different experimental wear simulations involving TKA components of low crosslinked polyethylene inserts, with two different loading patterns and knee kinematics conducted in an AMTI knee wear simulator: a low intensity and a high intensity. Wear coefficients incorporating contact pressure, sliding distance, and cross-shear were generated by inverse FEA using the experimentally measured volume of wear loss as the target outcome measure. The FE models and wear coefficients were validated by predicting wear in a mobile bearing UKA design.

Highly crosslinked polyethylene (XLPE). Two FEA models were constructed involving TKA and UKA XLPE inserts with different loading patterns and knee kinematics conducted in an AMTI knee wear simulator. Wear coefficients were generated by inverse FEA.


Full Access
Darryl D'Lima Shantanu Patil Adam Bunn Clifford Colwell

Background

Despite the success of total knee arthroplasty (TKA) restoration of normal function is often not achieved. Soft tissue balance is a major factor for poor outcomes including malalignment, instability, excessive wear, and subluxation. Computer navigation and robotic-assisted systems have increased the accuracy of prosthetic component placement. On the other hand, soft tissue balancing remains an art, relying on a qualitative feel for the balance of the knee, and is developed over years of practice

Several instruments are available to assist surgeons in estimating soft tissue balance. However, mechanical devices only measure the joint space in full extension and at 90° flexion. Further, because of lack of comprehensive characterization of the ligament balance of healthy knees, surgeons do not have quantitative guidelines relating the stability of an implanted to that of the normal knee. This study measures the ligament balance of normal knees and tests the accuracy of two mechanical distraction instruments and an electronic distraction instrument.

Methods

Cadaver specimens were mounted on a custom knee rig and on the AMTI VIVO which replicated passive kinematics. A six-axis load cell and an infrared tracking system was used to document the kinematics and the forces acting on the knee.

Dynamic knee laxity was measured under 10Nm of varus/valgus moment, 10Nm of axial rotational moment, and 200N of AP shear. Measurements were repeated after transecting the anterior cruciate ligament, after TKA, and after transecting the posterior cruciate ligament.

The accuracy and reproducibility of two mechanical and one electronic distraction device was measured.


Yifei Dai Jeffery Bischoff Kim Bertin Samih Tarabichi Ashok Rajgopal

INTRODUCTION

Balancing accurate rotational alignment, minimal overhang, and good coverage during total knee arthroplasty (TKA) often leads to compromises in tibial component fit, especially in smaller-sized Asian knees. This study compared the fit and surgical compromise between contemporary anatomic and non-anatomic tibial designs in Japanese patients.

METHODS

Size and shape of six contemporary tibial component designs (A:anatomic, B:asymmetric, C-F:symmetric) were compared against morphological characteristics measured from 120 Japanese tibiae resected following TKA surgical technique. The designs were then digitally placed on the resected tibiae. Each placement selected the largest possible component size, while ensuring <1mm overhang and proper alignment (within 5° of neutral rotational axis). When a compromise on either alignment or overhang was required (due to smaller-sized component unavailable), the design was flagged as “no suitable component fit” for that bone. Tibial coverage was compared across designs. Next, 32 femora were randomly selected from the dataset onto which each design was evaluated in two placements, the first maximizing coverage without attention to rotation and the second enforcing rotational accuracy. Downsizing was identified if in the second placement, enforcing rotational accuracy, required a smaller component size compared the first placement. The degree of mal-alignment while maximizing coverage, the incidence of downsizing, and difference in coverage between the two placements were compared across designs. Statistical significance was defined at p<0.05.


Yifei Dai Charles Penninger Jeffery Bischoff

INTRODUCTION

During total knee arthroplasty (TKA), the pursuit of accurate alignment, proper bone cuts, and good soft tissue balancing sometimes can result in the overhang of the femoral component, especially in smaller-sized Asian knees. As size and shape of the distal femur are highly variable, component designs that offer increased shape and size offerings may be desirable to fit the distal femur. This study tested the hypothesis that increased shape and size offerings in TKA femoral designs may improve their fit to the Japanese femur compared to designs that offer only one shape and limited sizes.

METHODS

Five contemporary femoral component designs were evaluated (Designs A-E). Design A has multiple mediolateral (ML) size offerings for a specific component anteroposterior (AP) size, and the finest increment (2mm) in AP sizes among all the designs. Designs B-E have single ML offerings across component AP sizes. For each design, virtual TKA resections were performed on the digital surfaces of 82 Japanese distal femora, each sized by selecting the component AP size that most closely matched but did not exceed the femoral AP dimension (Fig 1A,B). The aspect ratio (ML/AP) of the resected femora was regressed against the aspect ratio of their properly sized components per design. The closeness of each design to the perfect shape match was evaluated by the root-mean-square deviation (RMSD) of the deviations between the femoral bone and components. Differences in ML dimensions (overhang/underhang) between component and resected femora were calculated (Fig1C,D). The incidence of clinically significant femoral overhang (>3mm), in which component downsizing is required, were analyzed.


Sachin Daivajna Luciano Agnello Ali Bajwa Richard Villar

Introduction

Short-stem hip arthroplasty is gaining popularity as a method of treating hip arthritis in biologically younger patients. The potential benefit of using a short-stem is preservation of bone in the proximal femur for a future revision. We have compared the early clinical and radiological results of a short-stem hip arthroplasty versus a conventional total hip arthroplasty (THA) using a standard length femoral prosthesis with particular focus on functional outcome.

Methods

We evaluated a prospectively collected data on consecutive series of 249 patients, who underwent uncemented total hip arthroplasty at our institution. They were distributed into 2 groups: Group I, 125 patients received an uncemented short femoral stem (Mini Hip Arthroplasty (MHA), Corin, Cirencester) and Group II, 124 patients received a conventional uncemented femoral stem (Accolade, Stryker, Michigan) with mean follow up of 3.2 years (2–4). The characteristics of the two groups have been presented in Table I. Evaluation was based on plain radiographs performed at 6 months, 1 year and 2 years postoperatively, while their clinical status was assessed using the modified Harris hip score (mHHS) preoperatively and postoperatively at 6 weeks, 6 months, 1-year, 2-years and annually thereafter.


Hannah Darton Frederic Cegla Ravi Vaidyanathan Jonathan Jeffers

Objectives

Implant loosening is the most common reason for revision of total or partial knee replacement, but the patient complains of pain-not a loose implant. It would be a useful diagnostic tool to interrogate the implant to ascertain whether it remains well fixed or not, thus either confirming or eliminating this mode of failure. For such technology to be adopted by manufacturers, it must be extremely low cost and simple to build into an implant. We aim to develop a sensor that meets these requirements and, when embedded in an implant, can provide information on its fixation to the underlying bone. We have previously proven that, through impedance analysis of passive piezoelectric sensors, it is possible for such sensors to determine the cured state of cement with good correlation (0.7) to a surgeon's judgement (Darton et al, 2014). In this study we now look at how the impedance trances of the sensors can be interpreted to distinguish between tibial trays that are securely cemented in sawbone blocks and those with no cement in loose fitting sawbone blocks.

Method

Small piezoelectric sensors (12 mm diameter, 0.6 mm thickness) were attached using ethyl cyanoacrylate to the top of a small metal tibial tray analogue and wired to an Impedance Analyzer (AEA Technology Inc). The sensor was swept with an alternating current between 100KHz and 400KHz. Three readings were taken using a custom-built code in MATLAB and an average impedance trace was calculated. A pre-calibrated servo-mechanical testing machine (Instron) was used to carry out a pull-out test of the tray from the sawbone block. The force required to completely disengage the tray was recorded. The same tibial tray was then cemented to the same sawbone block using PMMA. Once cured, the same impedance readings were taken before a pull out test was performed on the cemented case. This was repeated on 6 different sawbone blocks

The impedance plots were differentiated to exaggerate the jagged nature of the impedance trace, representative of multiple modes of vibration following which the mean of their differential values was calculated. The average pull out force for cemented trays was approximately 20 times greater than the un-cemented.


Judd Day Daniel MacDonald Christina Arnholt Gerald Williams Charles Getz Matthew Kraay Clare Rimnac Steven Kurtz

INTRODUCTION

Mechanically assisted crevice corrosion of taper interfaces was raised as a concern in total hip arthroplasty (THA) approximately 20 years ago (Gilbert 1993). In total shoulder replacement, however, comparatively little is known about the prevalence of fretting assisted crevice corrosion or the biomechanical and patient factors that influence this phenomenon. Given the comparatively lower loading experienced in the shoulder compared to the hip, we asked: (1) What is the prevalence of fretting assisted corrosion in modular total shoulder replacements, and (2) What patient and implant factors are associated with corrosion?

METHODS

Modular components were collected from 48 revision shoulder arthroplasties as part of a multi-center, IRB approved retrieval program. For anatomic shoulders, this included 40 humeral heads, 32 stems and four taper adapters from seven manufacturers. For reverse shoulders, there were eight complete sets of retrieved components from three manufacturers. The components were predominantly revised for instability, loosening and pain. Anatomical shoulders were implanted for an average of 3.1 years (st dev 3.8; range 0.1–14.5). Reverse shoulders were implanted for an average of 2.2 years (st dev 0.7; range 1.3–3.3). Modular components were disassembled and examined for taper damage. The modular junctions were scored for fretting corrosion using a semi-quantitative four-point scoring system adapted from Goldberg, et al. (Goldberg, 2002, Higgs 2013). The scoring system criteria was adapted from Goldberg and Higgs which is comprised of a one to four grading system (with one indicating little-to-no fretting/corrosion and four indicating extensive fretting/corrosion). The component alloy composition was determined using the manufacturer's laser markings and verified by x-ray fluorescence. Patient age, gender, hand dominance, alloy, flexural rigidity of the trunnion and taper geometry were assessed independently as predictors for fretting corrosion.


Judd Day Reagan McCloskey Clare Rimnac Matthew Kraay Gerald Williams Joseph Abboud Steven Kurtz

INTRODUCTION

Retrieval analysis is an important aspect of medical device development. Examination of retrieved devices allows device developers to close the design loop, understand the performance of devices, and validate assumptions made and methods used during preclinical testing. We provide an overview of the implant retrieval analysis performed at the Implant Research Center at Drexel University on reverse total shoulder systems retrieved after short to medium term implantation.

METHODS

We have examined 18 reverse total shoulders, retrieved at revision surgery after short to mid-term implantation (average 1.4 years, maximum 3.3 years). The average age at revision was 71 years old (st dev 11 years). Our evaluations included analysis of glenosphere bearing surface damage, evaluation of tribocorrosion at the modular junctions, visual assessment of polyethylene humeral bearing surface damage, quantitative analysis of polyethylene wear.


Kirsten De Burlet James Widnall Cefin Barton Veera Gudimetla

Introduction

Enhanced Recovery Protocol (ERP) for elective total hip or total knee replacement has become the gold standard. The main principles are to reduce bleeding, both with a tranexamic acid infusion and local injection of adrenaline, and to reduce the risk of postoperative thrombo-embolic complications by early mobilisation, enabled by local anaesthetic infiltration at time of surgery. The aim of this study is to evaluate the impact of the ERP.

Methods

A retrospective review was performed including all patients who underwent primary hip or knee arthroplasty surgery between January 2011 and December 2013. The ERP was implemented in our department in August 2012 thus creating two cohorts; the traditional postoperative group and those undergoing ERP. Outcome measurements of length of stay, postoperative transfusion, thrombo-embolic complications and number of re-admissions were assessed.


Ivan De Martino Rocco D'Apolito Vincenzo De Santis Giorgio Gasparini

Background

Tapered cementless femoral components have been used in total hip arthroplasty (THA) constructs for more than 20 years. The Synergy femoral component was introduced in 1996 as a second generation titanium proximally porous-coated tapered stem with dual offsets to better restore femoral offset at THA (Figure 1). The purpose of this study was to evaluate the outcome of the authors' experience using the Synergy stem at minimum 15 years of follow-up.

Material and methods

We retrospectively reviewed a consecutive series of 102 patients (112 hips) who underwent surgery between November 1996 and October 1998 for primary THA using cementless Synergy stem with a minimum 15-years follow-up. The mean age at the time of surgery was 61 years, and the mean duration of follow-up was 16.3 years. Seventeen patients were lost at FU (8 died before the 15 years mark, 8 changed residency, 1 not willing to be seen) with no problems related to the replaced hip. Ninety-four hips in 85 patients were available for clinical and radiologic analysis. Clinical results of the 94 THAs with more than 15 years of follow-up were assessed preoperatively and postoperatively at 5, 10 and 15 years by means of standard evaluation tools: SF12, WOMAC and Harris Hip Score. Thigh pain frequency and intensity were also recorded. Radiographic analysis (Figure 2) was focused on stem alignment, bone ingrowth, radiolucent lines presence, width and progression, stress-shielding and heterotopic ossification (HTO). Student paired test and Kaplan-Meier survival analysis were used for statistical analysis.


Joseph Deck Bruce White

The Grood and Suntay coordinate system is a well-known framework for defining relative joint motions referenced to clinically meaningful anatomical directions. However, in general the Grood and Suntay unit vectors do not intersect at a point, and the “floating” (second) unit vector does not have a fixed location relative to the joint. These characteristics can introduce complications when analyzing joint forces such as the forces resulting from contact or from soft tissue structures. We have developed a methodology to address these issues by resolving forces along directions that intersect at a point fixed to one of the joint bodies. The work is demonstrated using Vivo Sim Control and Vivo Sim Visualization software.

The Vivo joint motion simulator, Figure 1, and Vivo Sim Visualization software were developed to investigate joint dynamics. They use the Grood and Suntay coordinate system. Figure 2, produced using Vivo Sim Visualization, shows a solid-body model of a knee, with Grood and Suntay frames in red and green. The light blue lines are a partial soft tissue model. Figure 3 is a representation of the Grood and Suntay coordinate system for a joint set in an arbitrary pose. Figure 3 shows the primary and secondary Grood and Suntay coordinate frames, labeled “F” and “T” (light arrows), the unit vectors e1, e2 and e3 (short dark arrows), and the displacement coordinates q1, q2, q3, α, β and γ. In general, there is no point in space about which there is zero net moment resulting from forces acting collinearly with the unit vectors. In order to obtain a zero-moment reaction condition, compensating moments must be computed and applied. In addition, because e2 floats, force collinear with that vector has a line of action that translates relative to the joint. These issues are inconvenient from an analytical standpoint and could be confusing for practitioners.

In Vivo's control system and in the Vivo Sim Visualization software, commanded joint forces and moments are resolved to axes parallel to the e1, e2 and e3 unit vectors but passing through the T origin. The origin of T is chosen to lie approximately collinear with the resultant of contact forces. A multi-fiber ligament model calculates forces collinear with the ligament fibers, which are resolved to equivalent forces and moments acting through the origin of T.

With this methodology, forces along anatomically-meaningful directions can be applied to or reported from the joint without the need to compute compensating moments. The lines of action of these forces can change orientation according to joint movements, but they always pass through a point fixed to the second body. We have implemented this methodology in the Vivo Joint Simulator and the Vivo Sim Visualization software.


Pierre Divine Philippe Anract Hamadouche Moussa David Biau

Introduction

Total hip replacement (THR) is one of the most widely used and most successful orthopedic procedures performed in developed countries. The burden of revision surgery, however, has become a major issue in terms of both volume and cost. Technical errors at the time of the index operation are known to be associated with an increased rate of revision.

Statistical methods, such as the CUSUM test, which have been developed for the manufacturing industry to monitor the quality of products, have come to the attention of health-care workers as a result of centers with protracted periods of inadequate performance. In orthopedics, these methods have been used to monitor the quality of total hip replacement in a tertiary care department using conventional imaging techniques.

Biplane low-dose X-ray imaging (EOS) may allow an easy, patient-friendly, way to retrieve data on the position of implants immediately postoperatively. Therefore real-time feedback is provided to surgeons and performance adjusted accordingly

Objectives

To assess the usefullness of EOS imaging in providing the position of implants immediately postoperatively


Philipp Dold Martin Bone Markus Flohr Roman Preuss Thomas J Joyce David Deehan Jim Holland

INTRODUCTION

Deformation of modular acetabular press-fit shells is a topic of much interest for surgeons and manufacturer. Such modular components utilise a titanium shell with a liner manufactured from metal, polyethylene or ceramic. Initial fixation is achieved through a press-fit between shell and acetabulum with the shell mechanically deforming upon insertion. Shell deformation may disrupt the assembly process of inserting the bearing liner into the acetabular shell for modular systems. This may adversely affect the integrity and durability of the components and the tribology of the bearing.

OBJECTIVE

Most clinically relevant data to quantify and understand such shell deformation can be achieved by cadaver measurements. ATOS Triple Scan III was identified as a measurement system with the potential to perform those measurements. The study aim was to validate an ATOS Triple Scan III optical measurement system against a co-ordinate measuring machine (CMM) using in-vitro testing and to check capability/ repeatability under cadaver lab conditions.


Benjamin Domb Asheesh Gupta Jon Hammarstedt Christine Stake Kinzie Sharp John Redmond

Background

Pre-operative and postoperative analgesia in total hip arthroplasty (THA) involves multimodal analgesia using differing classes of drugs and varying introductions of these agents. Postoperative opioid-related events can slow recovery and increase patients' length of stay. Long-acting local anesthetics can reduce early postoperative pain at the surgical site, potentiating a decrease of opioid intervention needed postoperatively. Decreasing opioid use while maintaining adequate pain control could reduce opioid-related events, increase patient time to first ambulation and decrease length of stay. The purpose of this study was to compare liposomal bupivacaine to bupivacaine for postoperative analgesia.

Methods

Between November 2012 and February 2013, 57 consecutive patients that underwent THA and hip resurfacing received either an intraoperative injection of liposomal bupivacaine or bupivacaine alone. All patients received a combination of medications prior to the procedure including celecoxib 400 mg by mouth, pregabalin 75 mg by mouth and 1gm of intravenous acetaminophen. The study group received 20 cc of liposomal bupivacaine, combined with 40 cc 0.25% bupivacaine with epinephrine and 20 cc of normal saline. The control group received 60 ml of 0.25% bupivacaine with epinephrine. Data was prospectively collected including average visual analog pain scale (VAS), opioid consumption, time to first ambulation, hospital length of stay measured by days, and post-operative opioid-related adverse drug events.


Michelle Burgett-Moreno Erla Medina Paul Burton Thomas Donaldson Ian Clarke

A 35-year-old female (age 35Yrs) had primary MOM total hip arthroplasty (THA) in 2008. At 8 months this patient postoperatively developed headaches, memory loss, vertigo, and aura-like symptoms that progressed to seizures. At 18 months review, she complained of progressive hip pain, a popping sensation and crepitus with joint motion. This patient weighed 284lbs with BMI of 38.5. Radiographs revealed the cup had 55° inclination, 39° anteversion (Fig. 1). Metal ion concentrations were high (blood: Co=126 mcg/L, Cr= 64mcg/L). Revision was performed in November 2010 A dark, serous fluid was observed, along with synovitis. The implants were well fixed and the femoral head could not be removed; thus the stem was removed by femoral osteotomy. With the head fused on this femoral stem, for the 1st time it was possible to precisely determine the habitual patterns of MOM wear relative to her in-vivo function. We investigated (1) size and location of wear patterns and (2) signs of cup-stem impingement to help explain her symptoms developed over 32 months follow-up.

The retrieved MOM was a Magnum™ with head diameter 50mm and 50×56mm cup (Biomet). This was mounted on a Taperloc™ lateralized porous-coated stem. Components were examined visually and wear damage mapped by stereo-microscopy, interferometry, CMM, SEM, and EDS. Main-wear zone (MWZ) areas were calculated using standard spherical equations1 and centroidal vectors determined.

The head-cup mismatch was 427um with the cup revealing a form factor of 228um. The cup showed wear area of 1275mm² that extended up to the cup rim over 150°arc. The cup rim was worn thin over a 90° arc with loss of cup bevel. The head showed an elliptical wear area of 2200mm2 located centrally on the superior-medial surface (ellipsoidal ratio ×1.2). Compared to the hemispherical surface (50mm: hemi-area = 3927mm2), the worn area represented hemi-area ratio of 56%. The centroidal vectors measured 8° anterior and 24° superior to the head's polar axis (Fig. 2). Stripe wear damage revealed multiple impingement sites. SEM and EDS revealed stripes were contaminated by metal transfer from the stainless-steel instruments used at revision. The main impingement position was identified (Fig. 3) indicating the site of repetitive subluxations whereby the subluxing head thinned the cup, i.e. “edge wear”.

Cup and head wear patterns corresponded well, reinforcing our definition of the MWZ locations in vivo. The femoral MWZ was centrally located superiorly and medially with respect to the polar axis of the femoral neck and head. The noted impingement position indicated this patient had experienced repetitive subclinical subluxations (RSS).2 The taper inside the fused head may also have been a contributory factor that we cannot ignore. Nevertheless her excessive cup thinning was likely a result of a steep cup and considerable anteversion allowing the femoral head to sublux over the cup rim, thus thinning the cup and wearing the rim bevel, and producing MOM wear debris.


Joseph Elsissy Alun John Evert Smith Thomas Donaldson Michelle Burgett-Moreno Ian Clarke

Metal-on-metal (MOM) retrieval studies have demonstrated that CoCr bearings used in total hip arthroplasty (THA) and resurfacing (RSA) featured stripe wear damage on heads, likely created by rim impact with CoCr cups.1-3 Such subluxation damage may release quantities of large CoCr particles that would provoke aggressive 3rd-body wear. With RSA, the natural femoral neck reduces the head-neck ratio but avoids risk of metal-to-metal impingement (Fig. 1).4 For this study, twelve retrieved RSA were compared to 12 THA (Table 1), evaluating, (i) patterns of habitual wear, (ii) stripe-wear damage and (iii) 3rd-body abrasive scratches. Considering RSA have head/neck ratios much lower than large-diameter THA, any impingement damage should be uniquely positioned on the heads.

Twelve RSA and THA retrievals were selected with respect to similar diameter range and vendors with follow-up ranging typically 1–6 years (Table 1). Patterns of habitual wear were mapped to determine position in vivo. Stripe damage was mapped at three sites: polar, equatorial and basal. Wear patterns were examined using SEM and white light interferometry (WLI). Graphical models characterized the complex geometry of the natural femoral neck in coronal and sagittal planes and provided RSA head-neck ratios.4

Normal area patterns of habitual wear were similar on RSA and THA bearings. The wear patterns showing cup rim-breakout proved larger for RSA cups than THA. Polar stripes presented in juxtaposition to the polar axis in both RSA and THA (Fig. 1). As anticipated, basal stripes on RSA occurred at steeper cup-impingement angles (CIA) than THA. The micro-topography of stripe damage was similar on both RSA and THA heads. Some scratches were illustrative of 3rd-body wear featuring raised lips, punctuated terminuses, and crater-like depressions (Fig. 2).

Neck narrowing observed following RSA procedures may be a consequence of impingement and subluxation due to the small head-neck ratios. However, lacking a metal femoral neck, such RSA impingement would not result in metal debris being released. Nevertheless it has been suggested that cup-to-head impingement produced large CoCr particles and also cup “edge wear” as the head orbits the cup rim.4 Our study showed that impingement had occurred as evidenced by the polar stripes and 3rd-body wear by large hard particles as evidenced by the wide scratches with raised lips. We can therefore agree with the prior study, that 2-body and 3rd-body wear mechanisms were present in both RSA and THA retrievals.


Nick Dong Tracy Rickels Adam Bastian Aiguo Wang Yixin Zhou Xianlong Zhang Yan Wang

Objective

The purpose of this study was to compare the proximal femoral morphology between normal Chinese and Caucasian populations by 3D analysis derived from CT data.

Materials and Methods

141 anonymous Chinese femoral CT scans (71 male and 70 female) with mean age of 60.1years (range 20–93) and 508 anonymous Caucasian left femoral CT scans (with mean age of 64.8years (range 20–93). The CT scans were segmented and converted to virtual bones using custom CT analytical software. (SOMA™ V.4.0) Femoral Head Offset (FHO) and Femoral Head Position (FHP) were measured from head center to proximal canal central axis and to calcar or 20mm above Lesser Trochanter (LT) respectively. The Femoral neck Anteversion (FA) and Caput-Collum-Diaphyseal (CCD) angles were also measured. The Medial Lateral Widths(MLWn) of femoral canal were measured at 0, -10, LT, -30, -40, -60, -70 and -100mm levels from calcar. Anterior Posterior Widths (APWn) were measured at 0, -60 and -100mm levels. The Flare Index (FI) was derived from the ratio of widths at 0 and -60mmor FI=W0/W−60. All measurements were performed in the same settings for both populations. The comparison was analyzed by Student T test. P<0.05 was considered significant.


Nick Dong Jim Nevelos Michael Nogler Timothy Lovell

Summary

Study showed a simple acetabular placement plane formed by pelvic landmarks. The plane was adjusted by changing one of the landmarks to a fixed value for best representing the native acetabular orientation based on CT generated 3D pelvi

Introduction

Correct acetabular cup placement is a critical step to prevent dislocation in the total hip arthroplasty. There are many mechanical alignment devices available but they are usually only referencing to the body long axis and the table therefore are lack of accuracy. Recently more accurate guide was achieved by image or imageless hip navigation system. But they add more cost, steps and time. The purpose of this study was to find a simple acetabular cup placement plane by selcting bonny land marks. The plane was adjusted with a fixed value by comparing it to native acetabular orientation in CT constructed 3D pelvi.


Sariali Elhadi Hugues Pascal-Moussellard

Introduction

Total hip arthroplaty (THA) using direct anterior minimal invasive (AMI) surgery is an attractive option to achieve a quicker habilitation. However, high complication rates were reported and very often related to technical difficulties at the time of surgery. We hypothesized that 3D preoperative planning may allow to anticipate these difficulties and to decrease the complications rates when using an AMI approach.

Material and methods

A prospective observational study included 191 consecutive patients who underwent a primary cementless THA using an AMI. A 3D CT-scan based pre-operative planning was performed in order to anticipate the potential difficulties that may be encountered especially regarding the hip anatomy reconstruction and the implants stability. The components size and position were planned in order to restore the leg length, the offsets, and the anteversions. Postoperatively, a CT scan was performed in order to compare the final anatomy to the planning.


Sariali Elhadi Hugues Pascal-Moussellard

Introduction

According to the literature, the gait does not return to normal after THA. However, the three-dimensional hip anatomy is usually not assessed before and after surgery. Our hypothesis was that an accurate reconstruction of the hip anatomy, based on a three-dimensional preoperative planning, may normalize the gait after THA.

Material and method

18 consecutive patients, graded Charnley A, aged of 59.3 ±13 years, underwent THA for unilateral primary osteoarthritis using a direct anterior minimal invasive approach. A 3D computerised planning was performed, the implants size and position were chosen in order to restore, the leg length, the off-set, the centre of rotation and the anteversion angles (Figure 1).

At 1 year follow up, a 3D gait analysis was performed and included 29 parameters describing the kinetics and the kinematics. Each patient was compared to himself using the contra-lateral healthy hip, as well as to a group of 13 healthy volunteers.


Gen Emoto

BACKGROUND

The aim of Patient-specific instrumentation surgery is to improve accuracy and limit the range of surgical variability. The main purpose of this study is to summarize and compare the radiographic outcomes of TKA performed using Patient-specific instrumentation compared with conventional techniques.

PURPOSES

In this study, we compared varus/valgus of the individual prosthesis components, rotation of femoral components and posterior slope of tibial components of 40 TKAs performed using a patient-specific technique with values from a matched control group of patients who were operated on by conventional intramedullary alignment technique.


Christina Esposito Brian Gladnick You-Yu Lee Stephen Lyman Timothy Wright David J Mayman Douglas E Padgett

Introduction

Acetabular component position is considered a major factor affecting the etiology of hip dislocation. The ‘Lewinnek safe zone’ has been the most widely accepted range for component position to avoid hip dislocation, but recent studies suggest that this safe zone is outdated. We used a large prospective institutional registry to ask: 1) is there a ‘safe zone’ for acetabular component position, as measured on an anteroposterior radiograph, within which the risk of hip dislocation is low?, and 2) do other patient and implant factors affect the risk of hip dislocation?

Materials and Methods

From 2007 to 2012, 19,449 patients (22,097 hip procedures) were recorded in an IRB approved prospective total joint replacement registry. All patients who underwent primary THA were prospectively enrolled, of which 9,107 patients consented to participate in the registry. An adverse event survey (80% compliance) was used to identify patients who reported a dislocation event in the six months after hip replacement surgery. Postoperative AP radiographs of hips that dislocated were matched with AP radiographs of stable hips, and acetabular position was measured using Ein Bild Röntgen Analyse software. Dislocators in radiographic zones (± 5°, ± 10°, ± 15° boundaries) were counted for every 1° of anteversion and inclination angles.


Alexander Mclawhorn Kaitlin Carroll Christina Esposito Joseph Maratt David J. Mayman

Background

Digital templating is a critical part of preoperative planning for total hip arthroplasty (THA) that is increasingly used by orthopaedic surgeons as part of their preoperative planning process. Digital templating has been used as a method of reducing hospital costs by eliminating the need for acetate films and providing an accurate method of preoperative planning. Pre-operative templating can help anticipate and predict appropriate component sizes to help avoid postoperative leg length discrepancy, failure to restore offset, femoral fracture, and instability. A preoperative plan using digital radiographs for surgical templating for component size can improve intraoperative accuracy and precision. While templating on conventional and digital radiographs is reliable and accurate, the accuracy of templating on digital images acquired with a novel biplanar imaging system (EOS Imaging Inc, Cambridge, MA, USA) remains unknown. EOS imaging captures whole body images of a standing patient without stitching or vertical distortion, less magnification error and exposes patients to less radiation than a pelvis AP radiograph. Therefore, the purpose of this study was to compare EOS imaging and conventional anteroposterior (AP) xrays for preoperative digital templating for THA, and compare the results to the implant sizes used intraoperatively.

Methods

Forty primary unilateral THA patients had preoperative supine AP xrays and standing EOS imaging. The mean age for patients was 61 ± 8 years, the mean body mass index 29 ± 6 kg/m2 and 21 patients were female. All patients underwent a THA with the same THA system (R3 Acetabular System and Synergy Cementless Stem, Smith & Nephew, TN, USA) by a single surgeon. Two blinded observers preoperatively templated using both AP xray and EOS imaging for each patient to predict acetabular size, femoral component size, and stem offset. All templating was performed by two observers with standard software (Ortho Toolbox, Sectra AB, Linköping, Sweden) [Figure 1] one week prior to surgery, and were compared using the Cronbach's alpha (∝) coefficient of reliability. The accuracy of templating was reported as the average percent agreement between the implanted size and the templated size for each component.


Mohamed Moussa Christina Esposito Marci Elpers Timothy Wright Douglas E Padgett

Introduction

Wear-related osteolysis continues to be a concern in the long-term outcome and survivorship of total hip arthroplasty (THA) and there continues to be an emphasis on bearing materials that exhibit improved wear profiles. Oxidized zirconium metal (Oxinium®, Smith & Nephew) was developed to reduce the amount of polyethylene wear as compared to cobalt chromium femoral heads, without the risk of brittle fracture seen with older generation ceramics. There are a limited number of retrieval studies evaluating the performance of Oxinium in THA. The aims of this study were 1) to visually assess damage on the surface of a large number of retrieved Oxinium femoral heads, 2) to measure surface roughness of scratches on the surfaces of Oxinium femoral heads, and 3) to use scanning electron microscopy (SEM) to assess the integrity of the oxidized zirconium surface in damaged areas. BIOLOX delta (CeramTec), a ceramic alternative to Oxinium, was included in this study for comparison.

Methods

From 2006 to 2013, 59 retrieved Oxinium femoral heads in THAs were collected after an average time to revision surgery of 1.64 years. The mean patient age was 61.9 years, with 32 males and 27 females. Reasons for revision surgery were recurrent dislocation (24), femoral component loosening or subsidence (13), infection (9), acetabular loosening (4), periprosthethic fracture (4), acetabular malposition (2), heterotopic ossification (2), and 1 case of leg length discrepancy. The diameters of the femoral heads were 28 mm (9), 32 mm (22), 36mm (26) and 40mm (2).

Three observers visually graded surface damage on all femoral heads according to the following criteria: 1) no scratches, 2) minimal damage with one to two scratches, 3) significant damage with multiple scratches. We measured the surface roughness of retrieved Oxinium and BIOLOX delta femoral heads with an interferomic profiler, and SEM to evaluate the extent of surface effacement.


Christina Esposito Theodore Miller Han Jo Kim David J. Mayman Seth A. Jerabek

Introduction

Pelvic flexion and extension in different body positions can affect acetabular orientation after total hip arthroplasty, and this may predispose patients to dislocation. The purpose of this study was to evaluate functional acetabular component position in total hip replacement patients during standing and sitting. We hypothesize that patients with degenerative lumbar disease will have less pelvic extension from standing to sitting, compared to patients with a normal lumbar spine or single level spine disease.

Methods

A prospective cohort of 20 patients with primary unilateral THR underwent spine-to-ankle standing and sitting lateral radiographs that included the lumbar spine and pelvis using EOS imaging. Patients were an average age of 58 ± 12 years and 6 patients were female. Patients had (1) normal lumbar spines or single level degeneration, (2) multilevel degenerative disc disease or (3) scoliosis. We measured acetabular anteversion (cup relative to the horizontal), sacral slope angle (superior endplate of S1 relative to the horizontal), and lumbar lordosis angles (superior endplates of L1 and S1). We calculated the absolute difference in acetabular anteversion and the absolute difference in lumbar lordosis during standing and sitting (Figure 1).


Full Access
Joseph Fetto

Thromboembolic (TE) events and related wound issues are the most common post-operative complications related to lower extremity total joint arthroplasty. They represent not only significant morbidity but also serious economic consequences. Evolution has selected for thrombus formation as a protection against exsanguination. Trauma is by definition a thrombogenic event. As surgery is an elective trauma, it is understandable that an individual undergoing a surgical procedure will be at increased risk to develop a TE event. However, to treat all patients with an identical prophylaxis denies the reality that the population is not homogeneous. Rather it is a normal distribution with wide variability from hemophyllic to thrombophyllic. As a consequence some patients may be over treated with resultant wound complications, i.e. hematomas, drainage, delaying discharge or worse requiring re-admisssion, re-operation or worst of all a secondary infection of the implanted device.

For this reason we proposed an inexpensive pre-operative screening protocol to more objectively identify an individual's levelof thrombophyllia. Although not exhaustive, it identifies those patients at ends of the curve with either an increased risk of clot or bleeding. It includes: Factor VIII, Factor V (Leyden), Factor C (APCR), Fibrinogen, D-dimer, Prothrombin Gene Mutation, ESR and CRP. This protocol costs less than $200/patient and was found to be 100% predictive of patient risk. Since instituting this protocol we have eliminated re-admission for complications related to overly aggressive TE prophylaxis. It has become an invaluable and intergral part of our pre-, intra- and post-operative protocol for multimodal TE prophylaxis.


Joseph Fetto

Recent introduction of short femoral implants has produced inconsistent outcomes. There have been reports of early aseptic failure as high as 30% within 2 years of implantation. This is in spite of the fact that these short components are shortened versions of existing successful non-cemented designs. The mode of initial fixation in non-cemented implants has been investigated. It has been demonstrated that long term survivability is dependent upon osseous integration; and that osseous integration requires secure initial implant fixation. Traditional non-cemented implants achieve initial fixation analogous to that of a nail in a piece of wood: friction and displacement (with resultant hoop stress). Initial fixation, of a traditional non-cemented femoral component, is directly proportional to surface area contact between the implant and endosteal bone and/or three point fixation. By reducing stem length, contact area may be significantly reduced, thereby increasing stresses over a smaller area of contact. The result of this is to potentially compromise fixation/implant stability against micromotion occurring in the early post-operative period. These stresses are most poorly resisted in flexion/extension and rotational planes about the long axis of the femur. In addition, force applied in an attempt to achieve initial fixation with a short stem may lead to an increased risk of periprosthetic fracture at the time of implantation.

We propose that there is an alternative mode of initial fixation, a “rest fit”, that may avoid both the risk of femoral fracture as well as provide better initial implant stability. To assure a maximal initial fixation and resistance to post-operative stresses which may compromise initial implant stability and osseous integration, a short implant should have three distinct geometric features: a medial and lateral flare, a flat posterior surface and a proximal trapezoidal cross section. The first will provide stability against subsidence and varus migration, by resting upon the proximal femur. A flat posterior surface will maximize load transmission to the femur in flexon/extension activities; and an asymmetrical proximal cross-section will provide resistance against rotational stresses about the long axis of the femur during activities such as stairclimbing. Together these features have been throproughly evaluated by FEA and in vitro testing. We are reporting on the shoprt term follow up (2.5 years avg.) first 300 short stems which have employed a “rest fit”. There have been no aseptic failures or revisions for mechanical failure of these implants.


Joseph Fetto

The stem of a femoral component can be helpful in assuring proper implant orientation. However, recent interest in short femoral components with which to better accommodate smaller incisions has resulted in technical challenges to proper implant positioning. In order to avoid component malposition and potential compromise of implant longevity, surgeons may rely upon intra-operative x-rays. However this has major drawbacks: radiation exposure of the OR staff; and accommodation of x-ray equipment without compromise of operating field sterility.

There has been created a simple, precise instrument which will ensure proper implant positioning in varus/valgus and flexion/extension planes without the need of intra-operative x-ray. Its reliability has been confirmed by both cadaveric and clinical studies. It has been demonstrated to be 100% accurate in providing proper short femoral component positioning.


Full Access
Oraldo Ricci Massimiliano Fini Mohammad H. Folath Alessandro Caprio

Since 2006 we have started to implant modular stelus, ceramic articolar component and Delta cotilus (PF 2006.2007 and TT since 2008) in hip artroplastic of young patients. 53 implantations (4 cases bilateral). Association with conic stelus (14th different shapes from 13 to 26) with trocanterical modulus that permits a good compliance studing each cases (offset-AR-lever-arm). We have found a good resolution using ceramic as matherial in articolar joint because reaching a very high level of satisfaction both for surgeons and for patients outfits. The Delta TT Lima has a titanium trabecular surface that offers a very good primary stability and a very high level in bone integration. The dedicated instrumentary, the design and the matherial high quality are the bases for a good resistance and a good articolar stability. Medium age of patients was 51 y.o. (from 33 to 66 y.o); follow up has been made at the 1st year and the 6th year. Results were evaluated following HHS guide line. Main treated pathologies were: primary arthrosis (9 cases); DCA (21 cases), post thraumatic arthrosis (9 cases), OA (8 cases), hip fractures (6 cases).


Clare K Fitzpatrick Chadd Clary Takayuki Nakamura Paul Rullkoetter

Introduction

The current standard for alignment in total knee arthroplasty (TKA) is neutral mechanical axis within 3° of varus or valgus deviation [1]. This configuration has been shown to reduce wear and optimally distribute load on the polyethylene insert [2]. Two key factors (patient-specific hip-knee-ankle (HKA) angle and surgical component alignment) influence load distribution, kinematics and soft-tissue strains across the tibiofemoral (TF) joint. Improvements in wear characteristics of TKA materials have facilitated a trend for restoring the anatomic joint line [3]. While anatomic component alignment may aid in restoring more natural kinematics, the influence on joint loads and soft-tissue strains should be evaluated. The purpose of the current study was to determine the effect of varus component alignment in combination with a variety of HKA limb alignments on joint kinematics, loads and soft-tissue strain.

Methods

A dynamic three-dimensional finite element model of the lower limb of a TKA patient was developed. Detailed description of the model has been previously published [4]. The model included femur, tibia and patella bones, TF ligaments, patellar tendon, quadriceps and hamstrings, and was virtually implanted with contemporary cruciate-retaining fixed-bearing TKA components. The model was initially aligned in ideal mechanical alignment with neutral HKA limb alignment. A design-of-experiments (DOE) study was performed whereby component placement was altered from neutral to 3° and 7° varus alignment, and HKA angle was altered from neutral to ±3° and ±7° (valgus and varus) (Figure 1).


Clare K. Fitzpatrick Takayuki Nakamura Yasuo Niki Paul Rullkoetter

Introduction

A large number of total knee arthroplasty (TKA) patients, particularly in Japan, India and the Middle East, exhibit anatomy with substantial proximal tibial torsion. Alignment of the tibial components with the standard anterior-posterior (A-P) axis of the tibia can result in excessive external rotation of the tibial components with respect to femoral component alignment. This in turn influences patellofemoral (PF) mechanics and forces required by the extensor mechanism. The purpose of the current study was to determine if a rotating-platform (RP) TKA design with an anatomic patellar component reduced compromise to the patellar tendon, quadriceps muscles and PF mechanics when compared to a fixed-bearing (FB) design with a standard dome-shaped patellar component.

Methods

A dynamic three-dimensional finite element model of the knee joint was developed and used to simulate a deep knee bend in a patient with excessive external tibial torsion (Figure 1). Detailed description of the model has been previously published [1]. The model included femur, tibia and patellar bones, TKA components, patellar ligament, quadriceps muscles, PF ligaments, and nine primary ligaments spanning the TF joint. The model was virtually implanted with two contemporary TKA designs; a FB design with domed patella, and a RP design with anatomic patella. The FB design was implanted in two different alignment conditions; alignment to the tibial A-P axis, and optimal alignment for bone coverage. Four different loading conditions (varying internal-external (I-E) torque and A-P force) were applied to the model to simulate physiological loads during a deep knee bend. Quadriceps muscle force, patellar tendon force, and PF and TF joint forces were compared between designs.


Kim Haeussler Christian Kruse Markus Flohr Roman Preuss Robert Streicher Michael Morlock

Introduction

For a safe design of ceramic components in total hip arthroplasty it is important to know the stress state within each part of the system under in vivo loading scenarios. Besides several design parameters, e.g. diametrical clearance between ball head and liner or angular mismatch in the taper region of metal shell and liner, also physiological factors, like patients' weight or bone quality, influence the stresses within the components. Therefore, the aim of the current study was to experimentally determine the stresses in a ceramic liner varying two of the factors: clearance and inclination angle of the liner.

Materials and Methods

Two ceramic liners were instrumented at the outer contour with five strain gauge (SG) rosettes (measuring grid length: 1.5 mm) on each liner (Fig.1). Metal shells were seated in an asymmetric press-fit Sawbones® model using a 0.5 mm under-reaming, and liners were afterwards axially assembled with a 2 kN load. SG5 was placed at the flat area of the liner, the other four were placed circumferentially in 90 degrees offset on the rear side of the liner. SG2 and SG4 were mounted opposite to each other in press-fit direction (contact of metal shell to the Sawbones® block) whereas SG1 and SG3 were placed in the non-supported direction (no contact of metal shell to the Sawbones® block). Four different inclination angles (0°, 30°, 45°, 60°) were tested under in vivo relevant loads of 4.5 and 11 kN. Two ceramic ball heads were used to examine a mid tolerance clearance and a clearance at the lower tolerance limit. Strain data was converted to stresses and compared using a paired two-sided Wilcoxon Rank Sum Test at an α-level of 0.05.


Mark Frame

Many orthopaedic procedures require implants to be trialled before definitive implantation. Where this is required, the trials are provided in a set with the instrumentation. The most common scenario this is seen in during elective joint replacements. In Scotland (2007) the Scottish Executive (http://www.sehd.scot.nhs.uk/cmo/CMO(2006)13.pdf) recommended and implemented individually packed orthopaedic implants for all orthopaedic sets. The premise for this was to reduce the risk of CJD contamination and fatigue of implants due to constant reprocessing from corrosion. During many trauma procedures determining the correct length of plate or size of implant can be challenging. Trials of trauma implants is no longer common place. Many implants are stored in closed and sealed boxes, preventing the surgeon looking at the implant prior to opening and contaminating the device. As a result many implants are incorrectly opened and either need reprocessed or destroyed due to infection control policy, thus implicating a cost to the NHS. With even the simplest implants costing several hundreds of pounds, this cost is a very significant waste in resources that could be deployed else where. My project was to develop a method to produce in department accurate, cheap and disposable trials for implants often used in trauma, where the original manufacturer do not offer the option of a trial off the shelf. The process had to not involve contaminating or destroying the original implant in the production of a trial.

Several implants which are commonly used within Glasgow Royal Infirmary and do not have trials were identified. These implants were then CT scanned within their sealed and sterile packaging without contamination. Digital 3D surface renders of the models were created using free open source software (OsiriX, MeshLab, NetFabb). These models were then processed in to a suitable format for 3D printing using laser sintering via a cloud 3D printing bureau (Shapeways.com). The implants were produced in polyamide PA220 material or in 316L stainless steel. These materials could be serialized using gamma irradiation or ethylene oxide gas. The steel models were suitable for autoclaving in the local CSSU.

The implants produced were accurate facsimiles of the original implant with dimensions within 0.7mm. The implants were cost effective, an example being a rim mesh was reproduced in polyamide PA220 plastic for £3.50 and in 316L stainless steel for £15. The models were produced within 10 days of scanning. The stainless steel trials were durable and suitable for reprocessing and resterilisation.

The production of durable, low cost and functional implant trials all completed in department was successful. The cost of production of each implant is so low that it would be offset if just one incorrect implant was opened during a single procedure. With some of the implants tested, the trials would have paid for themselves 100 times. This is a simple and cost saving technique that would help reduce department funding and aid patient care.


Amir Pourmoghaddam Stefan Kreuzer Adam Freedhand

Introduction

Cementless stems have been used in treatment of patients with osteoarthritis however, the new design concept of neck preserving stems also known as short femoral stems have been utilized to decrease the potentially adverse symptoms of the standard stems such as stress shielding and thigh pain. In this ongoing study we aim to demonstrate the clinical and radiographic outcome of direct anterior approach of total hip arthroplasty (THA) by using short stem prosthesis.

Methods

In this study, 390 total cases of THA in 345 patients who underwent an anterior approach of THA by using a short-stem prosthesis (Minihip, Corin) between 2009 and 2013 were reviewed.

This group included 282 male and 62 female patients. Table 1 summarizes the demographic information of the patients. In 48 cases avascular necrosis (AVN) was the diagnosis and 339 cases was reported to be due to osteoarthritis. Twenty eight patients were assessed to have American Society of Anesthesiologist (ASA) physical functional score of class I, 258 patients had class II, 103 had class III, and 1 had class IV. Table 2 shows the Charnley classification of the patients.

In the current study we evaluated the outcomes of the surgery by utilizing Hip Disability and Osteoarthritis Outcome Score (HOOS) subscales (Pain, Symptoms, Function in daily living (ADL), Function in sport and recreation (Sport/Rec) and Quality of life (QOL)).


Tadashi Fujii Yasuhito Tanaka Munehito Seko Marehoshi Nobori

Background

Bilateral leg alignment should be equal for preventing leg length discrepancy and diminishing limping in walking. The candidates for total knee arthroplasty (TKA) sometimes image bilateral TKA seems to get completely same shape and alignment of legs. The query that bilateral TKA, staged in a day and by one surgeon, has an advantage to reconcile one side alignment and component setting to another side, was investigated.

Materials and methods

This retrospective investigation enrolled 408 knees of 204 patients (74 years old on average) underwent one day TKA and 48 knees of 24 cases (73 years old on average) underwent two days TKA. There were no history of trauma and surgery on both legs and no other obvious features. All components were same (Vanguard PS TKA, Biomet Inc. Warsaw IN). Surgical procedure is single (modified gap technique) with intramedullar rod for the femur and extramedullar system for the tibia without navigation system and patient specific instrumentation (PSI). Postoperative femorotibial angle (FTA), α, β, γ, δ angles were computed and the absolutes of differences between right and left were analyzed. (two sample t test)


Yosuke Fujii Kazuo Fujiwara Hirosuke Endou Yohei Kagawa Toshifumi Ozaki Nobuhiro Abe Naohiko Sugita Mamoru Mitsuishi Takayuki Inoue Yoshio Nakashima

Background

CT-based navigation system in total hip arthroplasty(THA) is widely used to achieve accurate implant placement. The purpose of this study was to evaluate the influence of initial error correction according to the differences in the shape of the acetabulum, and correction accuracy associated with operation approach after localization of registration points at anterior or posterior area of the acetabulum.

Methods

We set the anterior pelvic plane(APP) as the reference plane, and defined the coordinates as follows: X-axis for external direction, Y-axis for anterior direction, and Z-axis for proximal direction. APP is defined by the anterior superior iliac spines and anterior border of the pubic symphysis. We made a bone model of bilateral acetabular dysplasia of the hip, after rotational acetabulum osteotomy(RAO) on one side, and performed registration using infrared-reflective markers. At first, we registered the initial error on navigation system, and calculated the accuracy of the error correction based on each shape of the acetabulum as we increased the surface matching points. Based on the actual operation approach, we also examined the accuracy of the error correction when concentrating the matching points in anterior or posterior areas of the acetabulum.


Hiroshi Fujita Tomoo Okumura Hiroaki Hara Hideto Harada Hiroshi Toda Ryuuichi Nishimura Tomohiro Tominaga

Background

Cement implantation syndrome characterized by hypotension, hypoxemia, cardiac arrhythmia or arrest has been reported in the literature. The purpose of the present study was to monitor blood pressure soon after cementing.

Methods

The present study includes 178 cases 204 joints of primary THA with an average age at operation of 64.5 years old (ranging 35 to 89). Under general anesthesia, both components were cemented using antero-lateral approach. Systolic arterial blood pressure during cementing acetabular and femoral components was monitored until 5 minutes with 1 minute interval. The maximum regulation ratio (MRR) was calculated as (maximum change blood pressure – blood pressure before cement insertion) divided by blood pressure before cement insertion.


Kazuo Fujiwara Hirosuke Endou Yohei Kagawa Yosuke Fujii Toshifumi Ozaki

Objectives

The shape of proximal femur is important for the selection of implant in total hip arthroplasty (THA). There are few reports about the shape of proximal femur. We analyzed preoperative and postoperative conditions of the proximal femurs of patients before and after total hip arthroplasty with computed tomography (CT) and evaluated the compatibility to the cementless stem.

Materials and Methods

We analyzed 65 hips of 63 patients (10 males and 53 females) who had THA between January 2008 and December 2010 in our hospital. We approximated the center of the femoral head as the center of the inscribed sphere in the femoral head. We defined the axis of proximal femur with the line between the centers of the circles located at 45 mm distal from lesser trochanter (LT) and at 90 mm proximal from LT. We measured the neck-shaft angle of femur, offset of femoral head, and diameter of bone-marrow cavity. After operation, we measured the distance between the stem surface and the edge of the femoral cortex (SF) at 10 mm proximal from LT to evaluate the compatibility of CT. We used PerFix HA cementless stem (Kyocera medical co., Osaka).


Takahiro Fukui Hirotaka Iguchi Yasuhiro Shibata

Introduction

For the total hip cases with severe bone defect, using acetabular reinforcement plate is one of effective method. But the shape of every defect is different. So it is very important to make it into proper shape. It would be not only time consuming but also the procedure requires many times trial insertion through the muscle which can be a cause big damage on it. To reduce the time and the damage, we have manufactured a chemical wood model for each case and shaped each acetabular reinforce plates.

Materials and Methods

Three total hip cases, one primary case of rheumatoid arthritis with big bone absorption and 2 revision cases with big bone absorption were operated with acetabular reinforcement plate (LIMA Italy) shaped on their pelvic chemical wood model. Using Mimics®, CAT scan DICOM data were transferred STL CAD data. Then using Magics® chemical wood model was designed and manufactured by a compact CNC machine. Then each plate was bent and fitted for each defect 3-Dimensionally.


Michihiko Fukunaga Shunji Hirokawa

There have been a large number of studies reporting the knee joint force during level walking, however, the data of during deep knee flexion are scarce, and especially the data about patellofemoral joint force are lacking. Deep knee flexion is a important motion in Japan and some regions of Asia and Arab, because there are the lifestyle of sitting down and lying on the floor directly. Such data is necessary for designing and evaluating the new type of knee prosthesis which can flex deeply. Therefore we estimated the patellofemoral and tibiofemoral forces in deep knee flexion by using the masculoskeltal model of the lower limb.

The model for the calculation was constructed by open chain of three bar link mechanism, and each link stood for thigh, lower leg and foot. And six muscles, gluteus maximus, hamstrings, rectus, vastus, gastrocnemius and soleus were modeled as the lines connecting the both end of insertion, which apply tensile force at the insertion on the links. And the model also included the gravity forces, thigh-calf contact forces on the Inputting the data of floor reacting forces and joint angles, the model calculated the muscle forces by the moment equilibrium conditions around each joint, and some assumptions about the ratio of the biarticular muscles. And then, the joint forces were estimated from the muscle forces, using the force equilibrium conditions on patella and tibia. The position/orientation of each segments, femur, patella and tibia, were decided by referring the literature.

The motion to be analyzed was standing up from kneeling posture. The joint angles during the motion are shown in Fig.1. This motion included the motion from kneeling to squatting, rising the knee from the floor by flexing hip joint, and the motion from squatting to standing. The test subject was a healthy male, age 23[years], height 1.7[m], weight 65[kgw].

Results were shown in Fig.2. The patellofemoral force was little at standing posture, the end of the motion, however, was as large as tibiofemoral force during the knee joint angle was over 130 degrees. The reason of this was that the patellofemoral joint force was heavily dependent on the quadriceps forces, and the quadriceps tensile force was large at deep knee flexion, at kneeling or squatting posture. The maximum tibiofemoral force was 3.5[BW] at the beginning of standing up from squatting posture. And the maximum patellofemoral force was 3.8[BW] at the motion from kneeling to squatting posture. The conclusion was that the patellofemoral joint force might not be ignored in deep knee flexion and the design of the knee prosthesis should be include the strength design of patellofemoral joint.


Shigenobu Fukushima Eita Togashi Hirobumi Sugawara Atsushi Narita Michiaki Takagi

It is very important for implanting tibial component to prevent bearing dislocation in Oxford UKA. One of the keys is accurate rotational position of tibia. But the problem remains what is accurate rotation of tibia in UKA.

Oxford Signature decided the rotation of tibia component from MRI images. We measured the component rotation of tibia using CT after operation.

Patients and Methods

14 patients were operated by Oxford Signature and 11 patients were operated by Microplasty method. Patients were examined by CT 2 or 3 weeks later after operation. We compared component axis of tibia and A-P axis by best fit circle, Akagi's line.

Results

In Oxford Signature group, component angle were 7.1 degree external rotation compared with A-P axis by best fit circle and were 3.6 degree external rotation compared with Akagi's line. In Microplasty group, component angle were 8.1 degree external rotation compared with A-P axis by best fit circle and were 3.8 degree external rotation compared with Akagi's line.


Kensuke Fukushima Rina Sakai Katsufumi Uchiyama Mitsutoshi Moriya Takeaki Yamamoto Naonobu Takahira Kiyoshi Mabuchi Masashi Takaso

Introduction

According to proposal of Noble, the femoral bone marrow cavity form of patients who underwent Total Hip Arthroplasty (THA) can be classified under 3 categories; those are Stovepipe, Normal and Champagne-fluted. We developed typical sodium chloride femoral model was created by 3D prototyping technique. The purpose was to identify the relationship of pressure zone of the surrounding areas between femoral bone marrow cavity form and hip stem.

Materials and Method

As opponent clarified stem design concept Zweymüller type model was used. According to CT data with the patients who underwent THA, the sodium chloride femoral model was custom-made and selected as the representative model based on Noble's 3 categories. Eight models of each category were used to performed mechanical test.


Moritoshi Furu Masahiro Ishikawa Shinichi Kuriyama Shinichiro Nakamura Masayuki Azukizawa Yosuke Hamamoto Hiromu Ito Shuichi Matsuda

Purpose

Total knee arthroplasty (TKA) is one of the most successful surgeries with respect to relieving pain and restoring function of the knee. However, some studies have reported that patients are not always satisfied with their results after TKA. The aim of this study was to determine which factors contribute to patient's satisfaction after TKA.

Methods

We evaluated 69 patients who had undergone 76 primary TKAs between March 2012 and June 2013, and assessed patient- and physician- reported scores using the 2011 Knee Society Scoring System and clinical variables before and after TKAs. We determined the correlation between patient satisfaction and clinical variables.


Olimpio Galasso Marco De Gori Raffaella Russo Giorgio Gasparini

High-dose antibiotic-loaded acrylic cement (ALAC) is used for managing periprosthetic joint infections (PJIs). The marked increase in resistant high-virulence bacteria is drawing the attention of physicians towards alternative antimicrobial formulations to the routinely used antibiotics. To date, few studies simultaneously investigated the elution properties of a broad range of antibiotics. The aim of thepresent in-vitrostudy was to determine the elution kinetics of 14 different high-dose ALACs.

All the ALAC samples showed a burst release of antibiotics in the first hour, progressively decreasing overtime, and elution curves strictly adhered to a non-linear regression analysis formula. Among aminoglycosides, commonly addressed as the most appropriate antibiotics to be loaded into the bone cement, the highest elution rate was that of tobramycin. Among the glycopeptides, commonly used to treat PJIs because of the prevalence of aminoglycoside resistance, vancomycin showed better elution in comparison with teicoplanin. Clindamycin, that can be associated with aminoglycosides to prepare ALACsshowed the highest absolute and relative elutions among all the tested formulations. A noticeable elution was also detected for colistin, an antibiotic of last resort for treating multi-drug resistant bacteria.

The current study demonstrates theoretical advantages in the preparation of ALAC for some antibiotics notroutinely used in the clinical setting for PJIs. The use of these antibiotics based on the infecting bacteria sensitivity may represent an useful option for physicians to eradicate PJIs. In vivo testing should be considered in the future to confirm the results of this study.


Bo Gao Nick Stroud Laurent Angibaud

Introduction

Cementless total knee arthroplasty (TKA) has several advantages compared to the cemented approach, including elimination of bone cement, a quicker and easier surgical technique, and potentially a stronger long-term fixation. However, to ensure the successful long-term biological fixation between the porous implant and the bone, initial press-fit stability is of great importance. Undesired motion at the bone-implant interface may inhibit osseointegration and cause failure of biological fixation. Initial stability of a cementless femoral implant is affected by implant geometry, bone press-fit dimension, and characteristics of the porous coating.

The purpose of this study was to compare the initial fixation stability of two types of porous femoral implants by quantifying the pull-out force using a paired cadaveric study design.

Methods

The two types of cementless TKA femoral implants evaluated in this study had identical implant geometry but different porous coatings (Figure 1). The first type had a conventional spherical-bead coating (Type A), while the second type had an innovative irregularly-shaped-powder coating (Type B). The porous coating thickness was equivalent for both types of implants, thus the dimensional press-fit with bone was also equivalent. Three pairs of cadaveric femurs were prepared using standard TKA surgical technique, with each pair of the femurs receiving one of each porous implant type.

An Instron 3366 load frame (Norwood, MA, USA) was used to pull the femoral implant out from the distal femur bone (Figure 2). The testing fixture was designed to allow free rotation between the implant and the actuator. The pullout was performed under a displacement control scheme (5 mm/min). Peak pull-out force was recorded and compared between the two implant groups.


Bo Gao Laurent Angibaud Diane Johnson

Introduction

Cruciate Retaining (CR) and Posterior Stabilizing (PS) are two common types of total knee arthroplasty (TKA) surgeries. The CR approach preserves the posterior cruciate ligament (PCL) while the PS approach sacrifices it. Implant size selection during a TKA surgery is primarily driven by the patient's bone size, but could also be affected by surgery types due to the influence of the PCL. The objective of this study was to investigate the effect of TKA surgery type on implant size selection, based on the clinical database of a well-established commercial implant system.

Methods

A clinical database operated by Exactech, Inc. (Gainesville, FL, USA) was utilized for this study. The database contains TKA patient information of Optetrak® implant recipients from over 30 physicians in the US, UK, and Colombia since 1995. Patient height was used as a control factor for comparison of surgery types, and categorized by every 10 cm (e.g., the “170 cm” category contains patients from 170 to 179 cm). Taking primary TKA only and body heights from 130 cm to 199 cm, a total of 2,677 cases were examined. No statistical difference exists on patients' gender, body weight, or BMI within every height category between the CR and PS groups. The femoral implant size and tibial insert thickness were compared between the two groups.


Bo Gao Laurent Angibaud Diane Johnson

Introduction

Total knee arthroplasty (TKA) implant systems offer a range of sizes for orthopaedic surgeons to best mimic the patient's anatomy and restore joint function. From a biomechanical perspective, the challenge on the TKA implants is affected by two factors: design geometry and in vivo load. Larger geometry typically means more robust mechanical structure, while higher in vivo load means greater burden on the artificial joint. For an implant system, prosthesis geometry is largely correlated with implant size, while in vivo load is affected by the patient's demographics such as weight and height. Understanding the relationships between implant size and patients' demographics can provide useful information for new prosthesis design, implant test planning, and clinical data interpretation. Utilizing a manufacturer supported clinical database, this study examined the relationships between TKA patient's body weight, height, and body mass index (BMI) and the received implant size of a well-established implant system.

Methods

A multi-site clinical database operated by Exactech, Inc. (Gainesville, FL, USA) was utilized for this study. The database contains patient information of Optetrak TKA implant recipients from over 30 physicians in US, UK, and Colombia since 1995. Nine implant sizes (0, 1, 2, 2.5, 3, 3.5, 4, 5 and 6) are seen in the database, while size 0 was excluded due to very low usage. Taking primary TKA only, a total of 2,713 cases were examined for patient's body weight, height, BMI, and their relationships with the implant size.


Eduardo Garcia-Cimbrelo

Different bearing surfaces, including alumina-on-alumina have been used to avoid osteolysis.

We ask if the use of modern ceramics matched with metal-backed sockets improves clinical results avoiding aseptic loosening, osteolysis and late dislocations.

We prospectively analysed 315 Cerafit cups in two different generations: First generation implanted between 1999 and 2005 (124 cups) and second generation (191 cups) all implanted with a 5-year minimum follow-up, and associated with a Multicone-HAP stem using alumina-on-alumina bearings. Patients' mean age was 48.7+13.6 years.

There were three dislocations within the first postoperative month and one early recurrent dislocation requiring reoperation using a double mobility cup. There were four intraoperative fractures, two in rheumatoid juvenile arthritis cases solved with a cerclage, and one postoperative fracture solved using a femoral long-stem. No fractures were seen in the alumina components in this series. Also, there have been no infections. There were 4 patients reporting non-reproducible squeaking. Survivorship analysis for cup loosening for any cause was 93% for group 1 (11 cups) and 99.2% for group 2 (1 cup in a patient with severe developmental dysplasia). The cumulative probability of not having a revision of one or both components for any cause was 96.9% (CI 95%:9.47–99.1%), All unrevised cases showed good clinical and radiographic results at the end of follow-up. No stem loosening, osteolysis nor stress shielding were found in any case by the end of follow-up. Changes in linear femoral head penetration were not seen in any hip.

These data suggest that Cerafit alumina-on-alumina prostheses show excellent results after fiften years. Cup loosening was more frequent in the cups of first generation, but not currently. Continued follow-up will be required to determine if reduction in wear between the alumina-on alumina bearings results in less osteolysis and loosening.


Eduardo Garcia-Rey Eduardo Garcia-Cimbrelo

Background

Cup migration and bone graft resorption are some of the limitations after acetabular impaction bone grafting (IBG) technique in revision hip surgery when used for large segmental defects. We asked whether the use of a metallic mesh may decrease the appearance of this complication. We compared the appearance of loosening in patients with a bone defect 3A or 3B according to Paprosky.

Materials and Methods

We assessed 204 hips operated with IBG and a cemented cup according to Slooff et al between 1997 and 2004. There were 100 hips with a preoperative bone defect of 3A and 104 with a 3B. We used 142 medial and/or rim metallic meshes for uncontained defects. The mean follow-up for unrevised cups was 10.4 years. We detemined postoperative radiological cup position and acetabular reconstruction of the hip center according to Ranawat in both groups. We assessed the appearance of radiological loosening and resorption of the graft.


Eduardo Garcia-Rey Eduardo Garcia-Cimbrelo

Introduction

Uncemented press-fit cups provide bone fixation in primary total hip replacement (THR). However, sometimes screws are needed to achieve primary stability of the socket. We analyzed biomechanical factors related to press-fit in seven cup designs and assessed whether screw use provides similar loosening rates to those of the press-fit technique.

Materials y Methods

From a series of 1,350 primary uncemented THRs using seven different press-fit cup designs (a dome loading hemispheric cup and bi- or tri- radius cups), we only analyzed the 889 diagnosed of primary osteoarthritis. All cases were operated by the same surgical team. The use of screws was decided intraoperatively based on cup stability according to the pull-out test. There were 399 female and 490 male patients with a mean age of 65 years old. The mean follow-up was 8.6 years (5–13 years). The reconstruction of the hip rotation center was evaluated according to Ranawat.


Eduardo Garcia-Rey Eduardo Garcia-Cimbrelo

Introduction

Dislocation is one of the most important complications after primary total hip replacement (THR). The low incidence of this finding makes it difficult to analyse the possible risk factors. The surgical technique can also influence this rate through cup position or an adequate reconstruction of the hip.

We assessed the demographic data and radiological reconstruction of the hip related to the appearance of dislocation after primary THR.

Material and Methods

1414 uncemented THRs were recorded from our Local Joint Registry. The mean age of the patients was 60.1 years old (range, 14 to 95), and the mean weight was 73.3 kg (42 to 121). There were 733 men and 974 patients were classified with an activity level of 4 or 5 according to Devane. The most frequent diagnosis was primary osteoarthritis, 795 hips, followed by avascular necrosis 207 hips. An alumina-on-alumina THR was implanted in 703 hips and a metal-on-polyethylene THR in 711 hips. A femoral head size of 28 mm was used in 708 hips and 32 mm in 704. Radiological cup position was assessed using the acetabular abduction angle, the height of the center of the hip, and the horizontal distance of the cup. Cup anteversion was measured according to Widmer and the reconstruction of the center of rotation of the hip according to Ranawat. The radiographic reconstruction of the abductor mechanism was measured using two variables: the lever arm and the height of the greater trochanter.


Rajnish Garg Sunny Gupta

Introduction

There is a growing recognition that evaluation should use patient-reported outcome tools and assessments of satisfaction in procedures like total knee replacement. These ensure that the patient's perception of outcome is included in the evaluation. Considering the increasing demands on physical function from the aging population, it is important to evaluate demanding physical activities for the population with end stage arthritis assigned for TKR.

Objectives

The aims of this prospective study were

To describe the outcome (from the patient's perspective) one year after TKR

To evaluate the patient satisfaction in terms of post op pain and functional outcome

To identify preoperative characteristics predicting the postoperative outcome.


Ryuichi Gejo Hiraku Motomura Isao Matsushita Kazuhito Sugimori Makiko Nogami Hayato Mine Tomoatsu Kimura

Introduction

Balancing of joint gap is a prerequisite in total knee arthroplasty (TKA). Recently, the tensor has been developed which can measure the joint gap with the patellofemoral joint reduced for more physiological assessment, and the results for osteoarthritis (OA) patients indicated that the flexion gap is larger than the extension gap during posterior-stabilized (PS) TKA. However with respect to the rheumatoid arthritis (RA) patients, the soft tissue balance in TKA is still unknown. Therefore, the purpose of this study was toinvestigate thecharacteristics of thejoint gap during TKAsurgeryforpatients with RA.

Methods

We implanted 90 consecutive knees with a PS TKA using a NexGen LPS-flex (Zimmer, Warsaw, IN). OA was the underlying disease in 60 knees and RA was the disease in30 knees.


Rajesh Ghosh Sohom Paul Yusuf Shahin Arif Rubel Abhik Paul Debanjan Saha

Introduction

Long-term success of the cementless acetabular component has been depends on amount of bone ingrowth around porous coated surface of the implant, which is mainly depends on primary stability, i.e. amount of micromotion at the implant-bone interface. The accurate positioning of the uncemented acetabular component and amount of interference fit (press-fit) at the rim of the acetabulum are necessary to reduce the implant-bone micromotion and that can be enhancing the bone ingrowth around the uncemented acetabular component. However, the effect of implant orientations and amount of press-fit on implant-bone micromotion around uncemented acetabular component has been relatively under investigated. The aim of the study is to identify the effect of acetabular component orientation on implant-bone relative micromotion around cementless metallic acetabular component.

Materials and Method

Three-dimensional finite element (FE) model of the intact and implanted pelvises were developed using CT-scan data [1]. Five implanted pelvises model, having fixed antiversion angle (25°) and different acetabular inclination angle (30°, 35°, 40°, 45° and 50°), were generated in order to understand the effect of implant orientation on implant-bone micromotion around uncemented metallic acetabular component. The CoCrMo alloy was chosen for the implant material, having 54 mm outer diameter and 48 mm bearing diameter [1]. Heterogeneous cancellous bone material properties were assigned using CT-scan data and power law relationship [1], whereas, the cortical bone was assumed homogeneous and isotropic [1]. In the implanted pelvises models, 1 mm diametric press-fit was simulated between the rim of the implant and surrounding bone. Six nodded surface-to-surface contact elements with coefficient of friction of 0.5 were assigned at the remaining portion of the implant–bone interface [1]. Twenty-one muscle forces and hip-joint forces corresponds to peak hip-joint force of a normal walking cycle (13%) were used for the applied loading condition. Fixed constrained was prescribed at the sacroiliac joint and pubis-symphysis [1]. A submodelling technique was implemented, in order to get more accurate result around implant-bone interface [1].