Introduction and Objective

The rupture of the anterior cruciate ligament is a common sports injury and surgical reconstruction is often required to restore full function of the knee. Hamstring tendons are usually used as autografts. In addition to knee pain and stiffness, infections are feared complications after surgery. Incubation of the autograft in a vancomycin solution until implantation reduced the infection rate by about ten-fold. Recent studies showed no negative effect of vancomycin on the biomechanical properties of porcine tendons. A negative effect of high vancomycin concentrations on chondrocytes and osteoblast is reported, but the effect on tendon and tenocytes is not known.

Introduction

Elevated remodelling of subchondral bone and marrow tissues has been firmly established as diagnostic and prognostic radiological imaging marker for human osteoarthritis. While these tissues are considered as promising targets for disease-modifying OA drugs, the development of novel treatment approaches is complicated by the lack of knowledge whether similar tissue changes occur in rodent OA models and poor understanding of joint-specific molecular and cellular pathomechanisms in human OA. Here, we describe the establishment of a human OA explant model to address this crucial niche in translational preclinical OA research.

Summary Statement

Cross-talk between cells from immune and bone system might play a role in molecular regulation of subchondral bone sclerosis in osteoarthritis. Macrophages, B-lymphocytes and tartrate-resistant acid phosphatase activity are specifically increased in sclerotic subchondral bone of patients with knee osteoarthritis.

Total hip replacement is one of the standard procedures in orthopedic surgery. Due to various reasons revision surgery (RTHR) has to be performed. In case of the revision of a cemented prosthesis stem, the bone cement has to be removed from the femoral cavity.

Conventionally the cement removal is done manually using a hammer, chisel or burr under X-ray control, causing a considerable radiation exposure for patient and the surgeon. Furthermore the risk of undesirable bone damage is high due to bad sight and access conditions, leading to complications and prolongation of the intervention. Different approaches addressing the mentioned problems were proposed, but did not achieve acceptance in clinical practice due to disadvantages concerning process controllability. Another possibility is to use a robot guided milling tool. However, to be able to control it typically a 3D reconstruction of the cement volume to be removed is necessary. Existing approaches use computed tomography based measurements combined with previously implanted markers, fluoroscopy or ultrasound based measurements, all requiring additional process steps prior to the surgery or to the actual cement removal.

The ICOS project (Impedance Controlled Surgical Instrumentation, Chair of Medical Engineering, RWTH Aachen University) investigates the approach of electrical impedance controlled, robot assisted bone cement removal, based on real time cement detection during the removal process without radiation exposure or the necessity of prior imaging or marker implanting steps. Therefore the electrical impedance is measured between the milling head mounted on the surgical mini-robot MINARO and one or more electrodes attached to the skin of the patient's thigh. An impedance variation mainly results from decreasing thickness of bone cement near the milling head contact point due to material removal. Hence the proposed method does not generate a 3D volume allowing for a milling path generation prior to the process. It requires a strategy for real time path generation using only the limited local information. Up to now, only the differentiation between bone cement and bone, and thus the cement-bone interface breakthrough, is reliably detectable. To efficiently use this information for the tool path generation, generic a-priori knowledge of the bone cement shape after removal of the prosthesis stem is used.

The concept for impedance controlled milling has been verified in first lab trials. For impedance measurements during the cement removal process the robots milling tool has been modified to achieve electrical insulation of the milling head. A strategy for online adaptive robot path planning has been implemented and tested in a Matlab/Simulink based process simulation. For all data sets a cement removal rate of about 90% with a bone removal of approximately 3% was achieved. These results confirm that it is generally possible to use only the limited local information for automated cement removal. Future work aims for a practical evaluation of the algorithm using real impedance measurement values.

This work has been funded by the German Ministry for Education and Research (BMBF) in the framework of the ICOS project under grant No. BMBF 13EZ1005.

Pertrochanteric femoral fractures are common and intramedullary nailing with a proximal femoral nail (PFNA®) is an accepted method for the surgical treatment. Accurate guide wire and subsequent hardware placement in the femoral neck is believed to be essential in order to avoid mechanical failure. Malpositioned implants may lead to rotational or angular malalignment or “cut out” in the femoral neck. Hip and knee arthritis might be a potential long-term consequence. The conventional technique might require multiple guidewire passes, and relies heavily on fluoroscopy.

A computer-assisted surgical planning and navigation system based on 2D-fluoroscopy was developed in-house as an intraoperative guidance system for navigated guide wire placement in the femoral neck and head. To support the image acquisition process, the surgeon is supported by a so-called “zero-dose C-arm navigation” module. This tool enables a virtual radiation-free preview of the X-ray images of the femoral neck and head. The aim of this study was to compare PFNA® insertion using this system to conventional implantation technique. We hypothesised that guide wire and subsequent implant placement using our software decreases radiation exposure to the minimum of two images and reduces the number of drilling attempts. Furthermore, accuracy of implant placement in comparison to the conventional method might be improved and operation time shortened.

We used 24 identical intact left femoral Sawbones® to simulate reduced pertrochanteric femoral fractures. First, we performed placement of the PFNA® into 12 Sawbones using the conventional fluoroscopic technique (group 1). Secondly, we performed placement of the PFNA® into 12 Sawbones guided by the computer-assisted surgical planning software (group 2). In each group, we first performed open and secondly minimal-invasive intramedullary nailing in six sawbones each. For minimal-invasive guide wire placement, a surgical drape imitated soft tissue coverage. Conventional and navigated technique used a C-arm fluoroscope (Siemens IsoC 3D®, Erlangen, Germany) in conventional 2D mode. Guidewire and subsequent blade placement in the femoral neck was evaluated. We documented: 1: the number of fluoroscopic images; 2: the total number of drilling attempts; 3: implant placement accuracy (3.1. Tip apex distance (TAD); 3.2. visible penetrations of the femoral neck and head; 3.3. blade-corticalis bone distance in the anteroposterior and lateral plane) and the 4: operation time.

The number of fluoroscopic single shots taken to achieve an acceptable PFNA®-blade position was reduced significantly with computer-assistance by 71.5% (p<0.001) in the open and by 72,4% (p<0.001) in the minimally invasive technique. In each operation two X-rays for final documentation were taken. The average number of drilling attempts for the computer-guided system was significantly (p<0.05) less than that of the conventional technique in the minimally invasive procedure. The average number of drilling attempts showed no difference between the computer-assisted and conventional techniques in the open procedure. Accuracy of implant placement showed no difference between the computer-assisted and the conventional group. Computer assistance significantly increased the mean operation time for fixation of pertrochanteric femoral fractures with a PFNA® by 79.8% (p<0.001) in the open technique and by 54.4% (p<0.001) in the minimally invasive technique.

Use of our computer-guided system for fixation of pertrochanteric femoral fractures by a PFNA® decreases the number of fluoroscopic single shots and of suboptimal guide wire passes while maintaining blade placement accuracy that is equivalent to the conventional technique. Computer-assisted surgery with our system increases the operation time and has just been tested in non-fractured sawbones. Although these results are promising, additional studies including fractured sawbones and cadaver models with extension of the navigation process to all steps of PFNA® introduction and with the goal of reducing the operation time are indispensable before integration of this navigation system into the clinical workflow.

Aim: Cycling is a common activity after TKA and it has been shown that up to 50 % of the TKA patients are riding a bike and 25 % think that cycling has an important place in their life. The specific contact mechanics of tibiofemoral joint is well known during walking, however, there is little data during cycling for TKA patients. The purpose of this study was to determine the tibiofemoral contact mechanics during cycling for TKA patients.

Methods: We recruited 10 patients implanted with a mobile bearing and 10 patients with a fixed bearing posterior stabilized prosthesis. An age-matched, asymptomatic control group consisted of 10 subjects. The patients were physically examined, and WOMAC index and knee society score were taken. Motion analysis was performed using a retroreflective marker based technique called “PCT”. Forces and moments during cycling were recorded with load cells at the crank shafts of the bike. Motion and load data were synchronized.

Results: Resultant pedal forces showed no significant differences between study groups but the generated impulse was higher in the mobile bearing group. Patients with contra-lateral osteoarthritis showed higher forces and impulse at the operated leg. The motion analysis showed the following mean values ±SD for TKA patients/Normals: maximum flexion angle 132.5° ±16.0°/131.5° ±18.3°, minimum flexion angle 41.4° ±12.0°/40.3° ±15.7°, range of rotation in transversal plane 12.6° ±4.7°/9.9° ±3.6° and range of anterior-posterior translation 5.3 mm ±5.1 mm/2.7 mm ±0.4 mm. There were no significant differences between study groups.

Discussion: In this study, force and impulse of TKA patients with contemporary prostheses were comparable to healthy subjects indicating functional restoration of the joint. Contralateral osteoarthritis may cause higher forces at the operated leg and thus, relatively higher stresses at the artificial articulation.

As expected, the generated forces at the bike pedal were low (20–25% body-weight) calling for little muscle activity and low compressive joint forces. However, with a mean maximum flexion angle of 131.5°, the observed motion ranges were higher than expected. Prostheses not designed for high flexion activities could lose tibio-femoral contact during cycling with detrimental effects on wear. Still, the measured range of rotation in the transverse plane indicates that despite its posterior-stabilized design rotation is taking place with approximately the same amount as it occurs in normal subjects. This may have detrimental effects on the post at the tibial plateau and could explain the previously observed rotational damage patterns on retrieved posterior stabilized TKA specimens.

Data are suggesting that leisure activities should be considered to determine the appropriate TKA design. This study will provide useful data for future design and wear testing scenarios.

OBJECTIVES: In recent years the incidence of proximal humerus fractures increased strongly. The optimal treatment of displaced, unstable fractures is still controversial. One of the major problem seen in previous treatment options was implant failure with secondary dislocation, pseudarthrosis and AVN. New angular stable implants promise a stronger anchorage and allow early functional aftertreatment, especially in osteopenic bone. Aim of this prospective case-series was to assess complication risks and functional outcome after ORIF with an angular stable form plate

DESIGN: Prospective case-series

SETTING: Multicenter study in 8 European Trauma Units

PATIENTS: 157 patients were treated for 158 displaced proximal humerus fractures

INTERVENTION: ORIF with a PHILOS^™ plate.

RESULTS: According to the AO/ASIF classification 25%, 61% and 37% were classified as type A, B and C, respectively. One year follow-up rate was 84%, whereupon 6 patients had died in the mean time and 18 were lost to follow-up. Overall 71 complications were observed in 53 patients and led to 39 unplanned re-operations, whereupon most frequent were primary screw perforations (n=22), secondary screw perforations (n=13)–mostly with secondary impaction (n=11), and AVN (n=8). Increasing age and severity of fractures influenced the occurrence of complications, since the risk to obtain a complication was doubled in patients over 60 years compared to younger (Relative Risk 1.9; Fischer’s Exact, p=0.022) as well as in AO/ASIF B- and C-fractures compared to A-fractures (Relative Risk=1.8; Fischer’s Exact, p=0.05). Risks for complications related to the implant, surgical technique or fracture and bone were 9%, 20% and 13%, respectively. Within one year all fractures healed and 5 secondary dislocations were observed. The mean (SD) Constant score of the injured shoulder improved during follow-up period to 72 points (15.2) at 12 months follow-up, when 87% (16.6%) of the contralateral shoulder was reached. Across all follow-up examinations the Constant score in relation to the contralateral shoulder impaired with increasing severity of the fracture (ANOVA, p=0.006). The mean (SD) DASH score after one year was with 16 points (21.1) worser (T-test, p< 0.001) than before the accident [5.2 (11.4)].

CONCLUSIONS: Fixation with a Philos plate provides high stability to preserve achieved reduction, which benefits the good functional outcome. However surgical technique related complication risks are high, particularly due to screw perforations into the joint. Augmented awareness and improvement of surgical technique should reduce these risks. Complex fracture types and higher age increases the risk to sustain complications, where as only severity of fractures impairs the functional outcome.

Introduction: There is an increasing tendency for internal fixation of proximal metaphyseal fractures. Intra-medullary nailing only recently has been considered to be a valuable option in these cases. Through the development of new reliable implant types, nailing finds increasing acceptance.

Questions: Is intramedually nailing with a new angle stable titanium nail a safe procedure in the treatment of proximal humeral fractures and is it combined with a good outcome?

Material and methods: A prospective international mul-ticenter study with standardized study control focused on the “Proximal Humeral Nail (PHN–Synthes Inc.), possible complications and clinical outcome. 151 fractures had been treated in 11 hospitals, where 72 were A-type, 67 B-type and 12 C-type (AO). There were 37 male, 114 female patients, median age 66 years ranging from 16 to 97 years. The outcome had been measured through Constant-Morley scores and DASH scores. 108 patients could be followed up until 1 year postoperatively.

Results: Important complications were perforation of the articular surface by screw or spiral blade (n=8), pain due to the implant (n=10), dislocation of fragments (n=2), non union (n=2), humeral head necrosis (n=3) and wound infection (n=1). The Constant-Morley score shows in total mean values one year postoperatively 75.3 in the injured and 89.9 in the non-injured side. The DASH score pre-operatively was in total 5.9 and 9.3 one year postoperatively, where the best results could achieve 0 points, the worst 100 points.

Discussion: Analyzing the complications, perforation of the articular surface by screw or spiral blade and pain due to the implant or impingement at the nail base are clearly related the technical failure in performing nailing. Here or the nail has not been introduced profoundly enough or the length for the spiral blade was not determined exactly and probably not controlled intraoperatively. This is due to the individual accuracy of the surgeon. The development of non-union (2/108) shows a ratio equal or even better to what is reported in conservative treatment or plate osteosynthesis. Dislocation of fragments n the other side, show the limit of this procedure, where in multifragmentary fracture type one spiral blade will not be able to fix a fragments. Using additional hardware is possible, but might reduce the effect of an initially low invasive approach. Constant score and Dash-score results perform similar to plate osteosynthesis, where clearly C-type-fractures present the worst prognosis.

Conclusion: Proximal humeral nailing seems to be beneficial in A-type metaphyseal fractures. Even in many B-type fractures it is still a good alternative with limited incision to the plate osteosynthesis.

In C-type fractures it is not advisable as a standard routine, only for experienced surgeons it might be a possible solution in selected cases.

Introduction: The Expert Tibia Nail was designed to address proximal, shaft, segmental and distal tibia fractures in one implant. Multiple locking options in various directions provide more stability and reduce the risk of secondary malalignment. Angle stable cancellous bone locking screws in the tibia head also improve fixation.

We evaluated this new implant in our series in a prospective, multicenter setting.

Methods: 190 patients were treated in 10 participating centers using the Expert Tibia Nail (Synthes). 127 patients suffered polytrauma, 58 presented as open fractures. Within the framework of the study 5 cases were proximal tibia fractures, 108 shaft fractures, 56 distal fractures, and 21 segmental fractures. These were followed-up postoperatively, after 3 months and one year and evaluated radiologically and clinically with regard to malalignment, union rate and complications.

Results: Non union occurred in 9 cases after one year of follow up (n=150). 20 patients showed delayed union. The rate of open and complex fractures was high in this group. Dynamisation was performed in 10 cases. Valgus/varus and recurvatum/antecurvatum malalignment of more than 5 degrees occurred in 13 cases. Stable reduction was achieved in 144 cases. In 4 complex fractures, initial reduction went into malalignment. 2 patients developed a deep infection after 3rd degree open fractures. 34 patients suffered from pain in the operated area. 6 screws broke during the follow-up.

Discussion: The Expert Tibia Nail proved to be an excellent tool to treat tibia fractures. Not only shaft fractures but also complex fractures in the proximal and distal metaphyseal area can be successfully stabilized due to advanced locking options and design of the nail. The rate of malalignment, non-union and complications was low.