Objective

Neurological injuries are most common complication, which has refrained many surgeons from opting elbow arthroscopy for indicated surgeries. The objective of this study was to evaluate the safety of anterolateral (AL) and posterolateral (PL) portals and chances of injury to the radial nerve and posterior interosseous nerve around the elbow joint during elbow arthroscopy.

Abstract

Total knee arthroplasty (TKA) is the most commonly performed elective orthopaedic procedure. With an increasingly aging population, the number of TKAs performed is expected to be ∼2,900 per 100,000 by 2050. Surgical Site Infections (SSI) after TKA can have significant morbidity and mortality. The purpose of this study was to construct a risk prediction model for acute SSI (classified as either superficial, deep and overall) within 30 days of a TKA based on commonly ordered pre-operative blood markers and using audited administrative data from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database.

All adult patients undergoing an elective unilateral TKA for osteoarthritis from 2011–2016 were identified from the NSQIP database using Current Procedural Terminology (CPT) codes. Patients with active or chronic, local or systemic infection/sepsis or disseminated cancer were excluded. Multivariate logistic regression was conducted to estimate coefficients, with manual stepwise reduction to construct models. Bootstrap estimation was administered to measure internal validity. The SSI prediction model included the following co-variates: body mass index (BMI) and sex, comorbidities such as congestive heart failure (CHF), chronic obstructive pulmonary disease (COPD), smoking, current/previous steroid use, as well as pre-operative blood markers, albumin, alkaline phosphatase, blood urea nitrogen (BUN), creatinine, hematocrit, international normalized ratio (INR), platelets, prothrombin time (PT), sodium and white blood cell (WBC) levels. To compare clinical models, areas under the receiver operating characteristic (ROC) curves and McFadden's R-squared values were reported.

The total number of patients undergoing TKA were 210,524 with a median age of 67 years (mean age of 66.6 + 9.6 years) and the majority being females (61.9%, N=130,314). A total of 1,674 patients (0.8%) had a SSI within 30 days of the index TKA, of which N=546 patients (33.2%) had a deep SSI and N=1,128 patients (67.4%) had a superficial SSI. The annual incidence rate of overall SSI decreased from 1.60% in 2011 to 0.68% in 2016. The final risk prediction model for SSI contained, smoking (OR=1.69, 95% CI: 1.31 – 2.18), previous/current steroid use (OR=1.66, 95% CI: 1.23 – 2.23), as well as the pre-operative lab markers, albumin (OR=0.46, 95% CI: 0.37 – 0.56), blood urea nitrogen (BUN, OR=1.01, 95% CI: 1 – 1.02), international normalized ratio (INR, OR=1.22, 95% CI:1.05 – 1.41), and sodium levels (OR=0.94, 95% CI: 0.91 – 0.98;). Area under the ROC curve for the final model of overall SSI was 0.64. Models for deep and superficial SSI had ROC areas of 0.68 and 0.63, respectively. Albumin (OR=0.46, 95% CI: 0.37 – 0.56, OR=0.33, 95% CI: 0.27 – 0.40, OR=0.75, 95% CI: 0.59 – 0.95) and sodium levels (OR=0.94, 95% CI: 0.91 – 0.98, OR=0.96, 95% CI: 0.93 – 0.99, OR=0.97, 95% CI: 0.96 – 0.99) levels were consistently significant in all prediction models for superficial, deep and overall SSI, respectively. Overall, hypoalbuminemia and hyponatremia are both significant risk factors for superficial, deep and overall SSI.

To our knowledge, this is the first prediction model for acute SSI post TKA whereby hyponatremia (and hypoalbuminemia) are predictive of SSI. This prediction model can help fill an important gap for predicting risk factors for SSI after TKA and can help physicians better optimize patients prior to TKA.

Background

Bone preservation is desired for future revision in any knee arthroplasty. There is no study comparing the difference in the amount of bone resection when soft tissue balance is performed with or without computer navigation.

To determine the effect on bony cuts when soft tissue balance is performed with or without use of computer software by standard manual technique in total knee arthroplasty.

One hundred patients aged 50 to 88 years underwent navigated TKR for primary osteoarthritis. In group A, 50 patients had both soft tissue release and bone cuts done using computer-assisted navigation. In group B, 50 patients had soft tissue release by standard manual technique first and then bone cuts were guided by computer-assisted navigation.

In group A the mean medial tibial resection was 5 ± 2.3 mm and lateral was 8 ± 1 mm compared to 5 ± 2 mm (P = 0.100) and 8 ± 1 mm respectively in group B (P = 0.860). In group A the mean medial femoral bone cut was 9 ± 2.9 mm and lateral was 8 ± 2 mm as compared to 9.5 ± 2.9 mm (P = 0.316) and 10 ± 2.2 mm respectively in group B (P = 0.001). Average prosthesis size was 6 (range 3 to 8) in group A as compared to size 5 (range 2 to 7) in group B. Average navigation time in group A was 102 minutes (range 45 to 172) and in group B was 83 minutes (range 42 to 165, P = 0.031).

Our results show that performing soft tissue release and bone cuts using computer- assisted navigation is more bone conserving as compared to manual soft tissue release and bone cuts using computer navigation for TKR, thus preserving bone for possible future revision surgery.

Introduction

Aim was to compare the functional outcome of anterior cervical decompression and fusion (ACDF) with stand-alone tricotical iliac crest auto graft verses stand-alone PEEK cage.

Background

Stress fractures at tracker after computer navigated total knee replacement are rare. Periprosthetic fracture after Minimally Invasive Plate Osteosynthesis (MIPO) of stress fracture through femoral tracker is unique in orthopaedic literature. We are reporting this unique presentation of periprosthetic fractures after MIPO for stress fracture involving femoral pin site track in computer assisted total knee arthroplasty, treated by reconstruction nail (PFNA).

During the preoperative examination, surgeons determine whether a patient, with a degenerative hip, is a candidate for total hip arthroplasty (THA). Although research studies have been conducted to investigate in vivo kinematics of degenerative hips using fluoroscopy, surgeons do not have assessment tools they can use in their practice to further understand patient assessment. Ideally, if a surgeon could have a theoretical tool that efficiently allows for predictive post-operative assessment after virtual surgery and implantation, they would have a better understanding of joint conditions before surgery.

The objectives of this study were (1) to use a validated forward solution hip model to theoretically predict the in vivo kinematics of degenerative hip joints, gaining a better understanding joint conditions leading to THA and (2) compare the predicted kinematic patterns with those derived using fluoroscopy for each subject.

A theoretical model, previously evaluated using THA kinematics and telemetry, was used for this study, incorporating numerous muscles and ligaments, including the quadriceps, hamstring, gluteus, iliopsoas, tensor fasciae latae, an adductor muscle groups, and hip capsular ligaments. Ten subjects having a pre-operative degenerative hip were asked to perform gait while under surveillance using a mobile fluoroscopy unit. The hip joint kinematics for ten subjects were initially assessed using in vivo fluoroscopy, and then compared to the predicted kinematics determined using the model. Further evaluations were then conducted varying implanted component position to assess variability.

The fluoroscopic evaluation revealed that 33% of the degenerative hips experienced abnormal hip kinematics known as “hip separation” where the femoral head slides within the acetabulum, resulting in a decrease in contact area. Interestingly, the mathematical model produced similar kinematic profiles, where the femoral head was sliding within the acetabulum (Figure 1).

During swing phase, it was determined that this femoral head sliding (FHS) is caused by hip capsular laxity resulting in reducing joint tension. At the point of maximum velocity of the foot, the momentum of the lower leg becomes too great for capsule to properly constrain the hip, leading to the femoral component pistoning outwards.

During stance phase, kinematics of degenerative hips were similar to kinematics of a THA subject with mal-positioning of the acetabular cup. Further evaluation revealed that if the cup was placed at a position other than its native, anatomical center, abnormal forces and torques acting within the joint lead to the femoral component sliding within the acetabular cup. It was hypothesized that in degenerative hips, similar to THA, the altered center of rotation is a leading influence of FHS (Figure 2).

The theoretical model has now been validated for subjects having a THA and degenerative subjects. The model has successfully derived kinematic patterns similar to subjects evaluated using fluoroscopy. The results in this study revealed that altering the native joint center is the most influential factor leading to FHS, or more commonly known as hip separation. A new module for the mathematical model is being implemented to simulate virtual surgery so that the surgery can pre- operatively plan and then simulate post-operative results.

Introduction

Many fluoroscopic studies on total knee arthroplasty (TKA) have identified kinematic variabilities compared to the normal knee, with many subjects experiencing paradoxical motion patterns. The intent of this research study was to investigate the results of customized-individual-made (CIM) and off-the-shelf (OTS) PS and PCR TKA to determine kinematic variabilities and to assess these kinematic patterns with those previously documented for the normal knee.

Introduction

Aim was to compare the functional outcome of anterior cervical decompression and fusion (ACDF) with stand-alone tricotical iliac crest auto graft verses stand-alone PEEK cage.

Introduction

Hip osteoarthritis can be debilitating, often leading to pain, poor kinematics and limiting range of motion. While the in vivo kinematics of a total hip arthroplasty (THA) are well documented, there is limited information pertaining to the kinematics of native, non-arthritic (normal) hips and degenerative hips requiring a THA.

The objective of this study is to evaluate and compare the in vivo kinematics of the normal hip with pre-operative, degenerative hips and post-operative THA.

Currently, hip implant designs are evaluated experimentally using mechanical simulators or cadavers, and total hip arthroplasty (THA) postoperative outcomes are evaluated clinically using long-term follow-up. However, these evaluation techniques can be both costly and time-consuming. Neither can provide an assessment of post-operative results at the onset of implant development. More recently, a forward-solution mathematical model was developed that functions as theoretical joint simulator, providing instant feedback to designers and surgeons alike. This model has been validated by comparing the model predictions with kinematic results from fluoroscopy for both implanted and non-implanted hips and kinetics from a telemetric hip. The model allows surgical technique modifications and implant component placement under in vivo conditions.

The objective of this study was to further expand the capabilities of the model to function as an intraoperative virtual surgical tool (Figure 1). This new module allows the surgeon to simulate surgery, then predict, compare, and optimize postoperative THA outcomes based on component placement, sizing choices, reaming and cutting locations, and surgical methods.

This virtual surgery tool simulates the quadriceps, hamstring, gluteus, iliopsoas, tensor fasciae latae, and an adductor muscle groups, as well as the hip capsular ligament groups. The model can simulate resecting, weakening, loosening, or tightening of soft tissues based on surgical techniques. Additionally, the model can analyze a variety of activities, including gait and deep flexion activities.

Initially, the virtual surgery module offers theoretical surgery tools that allow surgeons to alter surgical alignments, component designs, offsets, as well as reaming and cutting simulations. The virtual model incorporates a built-in CT scan bone database which will assist in determining muscle and ligament attachment sites as well as bony landmarks. The virtual model can be used to assist in the placement of both the femoral component and the acetabular cup (Figure 2).

Moreover, once the surgeon has decided on the placements of the components, they can use the simulation capabilities to run virtual human body maneuvers based on the chosen parameters. The simulations will reveal force, contact stress, and motion predictions of the hip joint (Figure 3). The surgeon can then choose to modify the positions accordingly or proceed with the surgery.

This new virtual surgical tool will allow surgeons to gain a better understanding of possible post-operative outcomes under pre-operative conditions or intra-operatively. Simulations using the virtual surgery model has revealed that improper component placement may lead to non-ideal post-operative function, which has been simulated using the model. Further evaluation is ongoing so that this new module can reveal more information pre-operatively, allowing a surgeon to gain ample information before surgery, especially with difficult and revision cases.

Introduction

Previous fluoroscopic studies of total knee arthroplasty (TKA) have revealed significant kinematic differences compared to the normal knee. Often, subjects having a TKA experienced kinematic patterns opposite of the normal knee. Therefore, the objective of this study was to determine the in vivo kinematics of subjects implanted with either a customized-individual-made (CIM) or the traditional (OTS) PS TKA to determine if customization offers a distinct advantage to the patient.

Background

The overall goal of total knee arthroplasty (TKA) is to facilitate the restoration of native function following late stage osteoarthritis and for this reason it is important to develop a thorough understanding of the mechanics of a normal healthy knee.

While there are several methods for assessing TKA mechanics, these methods have limitations that make them prohibitive to both replicating physiological systems and evaluating non-implanted knees. These limitations can be circumvented through the development of mathematical models that use anatomical and physiological inputs to computationally simulate joint mechanics. This can be done in an inverse or forward manner to solve for either joint forces or motions respectively. The purpose of this study is to evaluate one such forward model and determine the accuracy of the predicted motions using fluoroscopy.

Background

In vivo fluoroscopic studies have proven that femoral head sliding and separation from within the acetabular cup during gait frequently occur for subjects implanted with a total hip arthroplasty. It is hypothesized that these atypical kinematic patterns are due to component malalignments that yield uncharacteristically higher forces on the hip joint that are not present in the native hip. This in vivo joint instability can lead to edge loading, increased stresses, and premature wear on the acetabular component.

Background

Extensive research has previously been conducted analyzing the biomechanical effects of rotational changes (i.e. version and inclination) of the acetabular cup. Many sources, citing diverse dislocation statistics, encourage surgeons to strive for various “safe zones” during the THA operation. However, minimal research has been conducted, especially under in vivo conditions, to assess the consequences of cup translational shifting (i.e. offsets, medial and superior reaming, etc.). While it is often the practice to medialize the acetabular cup intraoperatively, there is still a lack of information regarding the biomechanical consequences of such cup medializations and medial/superior malpositionings.

Background

Previous in vivo fluoroscopic studies have documented that subjects having a PS TKA experience a more posterior condylar contact position at full extension, a high incidence of reverse axial rotation and mid flexion instability. More recently, a PS TKA was designed with a Gradually Reducing Radius (Gradius) curved condylar geometry to offer patients greater mid flexion stability while reducing the incidence of reverse axial rotation and maintaining posterior condylar rollback. Therefore, the objective of this study was to assess the in vivo kinematics for subjects implanted with a Gradius curved condylar geometry to determine if these subjects experience an advantage over previously designed TKA.

Background

The Bi-Cruciate Stabilized (BCS) total knee arthroplasty (TKA) incorporates two cam-post mechanisms in order to replicate the functionality and stability provided by the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) in the native knee. Recently (2012), a second generation BCS design has introduced femur and tibial bearing modifications that are intended to delay lateral femoral condyle rollback and encourage more stable positioning of the medial femoral condyle to more closely replicate normal knee kinematics. The purpose of this study was to compare the kinematics of this TKA to the normal knee during a weight bearing flexion activity.

Background

Currently, hip implant designs are evaluated experimentally using mechanical simulators or cadavers, and total hip arthroplasty (THA) postoperative outcomes are evaluated clinically using long-term follow-up. However, these evaluation techniques can be both costly and time-consuming. Fortunately, forward solution mathematical models can function as theoretical joint simulators, providing instant feedback to designers and surgeons alike. Recently, a validated forward solution model of the hip has been developed that can theoretically simulate new implant designs and surgical technique modifications under in vivo conditions.

Introduction

The Bi-Cruciate Stabilized (BCS) total knee arthroplasty (TKA) incorporates two cam-post mechanisms to reproduce the functionality and stability provided by the anterior cruciate ligament and posterior cruciate ligament in the native knee. The anterior cam-post mechanism provides stability in full extension and early flexion (≤20°) while the posterior cam-post mechanism prevents anterior sliding of the femur during deeper flexion (≥60°). Recently (2012), a second generation BCS design introduced more normal shapes to the femur and tibial bearing geometries that provides delayed lateral femoral condyle rollback and encourages more stable positioning of the medial femoral condyle. The purpose of this study was to compare the in vivo kinematics exhibited by the two generations during weight bearing flexion.

Background

While not common in the native hip, occurrences of femoral head separation from the acetabular cup during gait are well documented after total hip arthroplasty. Although the effects of this phenomenon are not well understood, we hypothesize that these atypical kinematics are due to component misalignments that yield uncharacteristic forces on the hip joint that are not present in the native hip.