No Major Functional Benefit After Bicompartmental Knee Arthroplasty Compared to Total Knee Arthroplasty at 5-Year Follow-Up.

BACKGROUND: In case of isolated medial and patellofemoral joint arthritis, bicompartmental knee arthroplasty (BCA) is an alternative to total knee arthroplasty (TKA). The purpose of our prospective, randomized study is to compare the clinical outcome of BCA vs TKA. METHODS: Eighty patients with isolated medial and patellofemoral osteoarthritis were randomly assigned to either BCA or TKA. Patients were evaluated preoperatively, 3, 6, and 12 months, and 2 and 5 years after the procedure. Knee Society Score, Oxford Knee Score, and the University of California,Los Angeles activity scores were calculated at each follow-up; Forgotten Joint Score was assessed at final follow-up. RESULTS: There was an improvement in Knee Society Score, Oxford Knee Score, and the University of California,Los Angeles scores in both groups but no significant differences between both groups at any follow-up. The Forgotten Joint Score at 5-year follow-up was not significantly different either. Range of motion was significantly greater in the BCA group from 1-year follow-up onward. CONCLUSION: Our study did not show significant differences in clinical scores between BCA and TKA; only range of motion was significantly greater in BCA. Therefore, it is questionable whether this difference justifies the complexity of BCA associated with higher risk of failure. Maybe staged patellofemoral joint arthroplasty in the presence of a well-functioning UKA is an option for BCA and an alternative to revision to TKA. Long-term studies are needed to explore the potential benefits of BCA.

Post-arthroscopic osteonecrosis of the medial tibial plateau: a case series.

BACKGROUND: Avascular necrosis after arthroscopic surgery of the knee has already been published. The purpose of this article is to report on the frequently misdiagnosed entity of osteonecrosis of the medial tibial plateau. CASE PRESENTATION: Charts and radiographs of a consecutive series with isolated medial tibial plateau osteonecrosis were analyzed. The criterion for inclusion was the absence of trauma. Six caucasian female patients with an average age of 76.5 years complied with this criterion. Three of these cases had had arthroscopic intervention for medial meniscal lesion within the previous year. CONCLUSIONS: The etiology of these necroses remains unclear. Osteonecrosis must be taken into account as a possible cause of persistent knee pain after surgery. Correlation between arthroscopic treatment and necrotic processes in the tibial plateau must still be regarded with skepticism.

Major acetabular defects treated with the Burch-Schneider antiprotrusion cage and impaction bone allograft in a large series: a 5- to 7- year follow-up study.

INTRODUCTION: Major bone defects are the greatest challenge in hip revision arthroplasty. METHODS: In a prospective, consecutive nonrandomised study we followed up 74 patients with Type III (AAOS) acetabular bone defects who underwent revision hip arthroplasty with bone grafting and implantation of a Burch-Schneider anti-protrusion cage (APC). The patients were examined pre- and postoperatively according to a standardised clinical and radiological protocol. No patient was lost to follow-up. RESULTS: 9 patients died before follow-up. In 9 other patients the APC was revised within the follow-up period. In 4 of these patients the revision was necessary because of aseptic loosening. In the remaining 5 cases joint infection, recurrent dislocation and 1 trauma were the reasons for revision. 56 patients were included in the statistical analysis. In the follow-up group the mean Harris Hip Score increased from 39.9 preoperatively to 73.2. 85% of the patients assessed their operation result as good or excellent. CONCLUSIONS: In a large consecutive series the Burch-Schneider anti-protrusion cage proved to be a valuable option in the treatment of major acetabular bone defects in hip revision surgery.

Friction in total hip joint prosthesis measured in vivo during walking.

Friction-induced moments and subsequent cup loosening can be the reason for total hip joint replacement failure. The aim of this study was to measure the in vivo contact forces and friction moments during walking. Instrumented hip implants with Al2O3 ceramic head and an XPE inlay were used. In vivo measurements were taken 3 months post operatively in 8 subjects. The coefficient of friction was calculated in 3D throughout the whole gait cycle, and average values of the friction-induced power dissipation in the joint were determined. On average, peak contact forces of 248% of the bodyweight and peak friction moments of 0.26% bodyweight times meter were determined. However, contact forces and friction moments varied greatly between individuals. The friction moment increased during the extension phase of the joint. The average coefficient of friction also increased during this period, from 0.04 (0.03 to 0.06) at contralateral toe off to 0.06 (0.04 to 0.08) at contralateral heel strike. During the flexion phase, the coefficient of friction increased further to 0.14 (0.09 to 0.23) at toe off. The average friction-induced power throughout the whole gait cycle was 2.3 W (1.4 W to 3.8 W). Although more parameters than only the synovia determine the friction, the wide ranges of friction coefficients and power dissipation indicate that the lubricating properties of synovia are individually very different. However, such differences may also exist in natural joints and may influence the progression of arthrosis. Furthermore, subjects with very high power dissipation may be at risk of thermally induced implant loosening. The large increase of the friction coefficient during each step could be caused by the synovia being squeezed out under load.

Peri-prosthetic femoral fractures treated with the uncemented Wagner revision stem.

The clinical and radiological results of Vancouver type B2 and B3 peri-prosthetic fractures treated with an uncemented Wagner revision stem (3rd generation) were analysed. Two groups were identified, 15 patients had a B2 and 14 cases a B3 periprosthetic fracture. The mean follow-up was 74 months after the index operation. All fractures had united radiographically. No cases of non-union were found. There was only one case of aseptic loosening. The clinical scores presented encouraging results for both groups. The uncemented distal fixation stem was an effective solution in the treatment of type B2 and B3 periprosthetic femur fractures at mid-term follow up.

Influence of limb alignment on mediolateral loading in total knee replacement: in vivo measurements in five patients.

BACKGROUND: Malalignment after total knee replacement could cause overloading of the implant bearing as well as of the bone itself, leading to osteolysis and early loosening. To quantify the stresses the implant has to withstand and to define a safe zone of limb alignment, the total contact forces as well as their mediolateral distribution have to be determined. Analytical gait data and mathematical models have been used for this purpose. We performed this study to determine in vivo loads of five patients after implantation of an instrumented tibial baseplate. METHODS: Five patients with osteoarthritis of the knee received total knee replacement. The tibial component was instrumented with strain gauges for the measurement of three forces and three moments. The signals from the gauges were transferred telemetrically to an external receiver. At twelve months after surgery, postoperative measurements were obtained with the patients walking at a self-selected comfortable speed across a level walkway. Peak axial and medial forces of fifteen to twenty gait cycles were averaged and reported as a percent of individual body weight. RESULTS: During the stance phase of the gait cycle, two maxima of the axial force occurred. Typical values were 215% of body weight at the first peak and 266% of body weight at the second peak. The medial load share was typically 73% at the first axial force peak and 65% at the second axial force peak. Analysis of inter-individual variations revealed a linear correlation with limb alignment. A deviation of 1° varus from neutral alignment increased the medial load share by 5%. CONCLUSIONS: Consistent with the results of previous studies, we found that the force transferred by the medial compartment was usually greater than that transferred by the lateral compartment. Concerning the design of total knee replacements, an asymmetric tibial component with a larger medial contact area could possibly reduce peak contact stress on the bone and improve fixation of the implant. Mediolateral load distribution was quantified and correlated with limb alignment, thereby permitting the effects of malalignment after total knee replacement to be estimated.

Loading of the knee joint during ergometer cycling: telemetric in vivo data.

STUDY DESIGN: Within-subject, repeated-measures design. OBJECTIVES: To measure tibiofemoral contact forces during cycling in vivo and to quantify the influences of power, pedaling cadence, and seat height on tibiofemoral contact forces. BACKGROUND: Cycling is usually classified as a low-demand activity for the knee joint and is therefore recommended for persons with osteoarthritis and rehabilitation programs following knee surgery. However, there are limited data regarding actual joint loading. METHODS: Instrumented knee implants with telemetric data transmission were used to measure the tibiofemoral contact forces. Data were obtained in 9 subjects, during ergometer cycling and walking, 15 ± 7 months after total knee arthroplasty. Tibiofemoral forces during cycling at power levels between 25 and 120 W, cadences of 40 and 60 rpm, and 2 seat heights were investigated. RESULTS: Within the examined power range, tibiofemoral forces during cycling were smaller than those during walking. At the moderate condition of 60 W and 40 rpm, peak resultant forces of 119% of body weight were measured during the pedal downstroke. Shear forces ranged from 5% to 7% of body weight. Forces increased linearly with cycling power. Higher cadences led to smaller forces. A lower seat height did not increase the resultant force but caused higher posterior shear forces. CONCLUSION: Due to the relatively small tibiofemoral forces, cycling with moderate power levels is suited for individuals with osteoarthritis and rehabilitation programs following knee surgery, such as cartilage repair or total knee replacement. The lowest forces can be expected while cycling at a low power level, a high cadence, and a high seat height.

[Reconstruction of the acetabulum with structured bone graft in press-fit technique]. / Rekonstruktion des Azetabulums mit strukturiertem Knochentransplantat in Press-fit-Technik.

OBJECTIVE: Reconstruction of defects of the superior acetabular rim with structured bone grafts in press-fit technique before total hip replacement. INDICATIONS: Defects of the superior acetabular rim following hip dysplasia Crowe type II-IV, avascular necrosis of the femoral head Ficat stage IV, or aseptic loosening of the cup with acetabular defects Paprosky type 2a and 2b. CONTRAINDICATIONS: Acetabular defects Paprosky type 2c, 3a and 3b, septic loosening, severe osteoporosis. SURGICAL TECHNIQUE: Exposure of the acetabular defect and debridement with a spherical reamer to create a concave bleeding graft bed. Shaping of the bone graft with an inverted reamer of corresponding size and oscillating saw. Press-fit insertion of the bone graft into the defect and temporary fixation with Kirschner wires. Rereaming of the acetabulum with the spherical reamer. Implantation of a cemented cup of corresponding size. Removal of Kirschner wires after setting of cement. POSTOPERATIVE MANAGEMENT: Full weight bearing in case of small or medium graft, 6-week non-weight bearing in case of big load-bearing graft. Mobilization on 1st day postoperatively. Stair climbing on 7th day postoperatively. Suture removal after 10 days. RESULTS: In 46 patients with 55 total hip replacements with structured grafts in press-fit technique, the Harris Hip Score improved from 38.9 points to 92.3 points after 29.4 months (12.0-84.4 months). There were two cases of delayed wound healing and one cup exchange because of aseptic loosening. Radiologically, one graft sintering by 5 mm was detected.

[Mini-subvastus approach for total knee replacement]. / Mini-Subvastus-Zugang bei der Implantation von Knieendoprothesen.

OBJECTIVE: Total knee replacement in minimally invasive technique without any trauma to the extensor apparatus and with soft-tissue-referenced bone resections. Only the subvastus approach preserves the integrity of the extensor apparatus and has therefore been modified to become a minimally invasive technique with a shorter skin incision and lateralization instead of eversion of the patella. Soft-tissue balancing is done through this direct anterior approach. INDICATIONS: Mild to moderate varus osteoarthritis of the knee up to 15 degrees of malalignment, mild and passively correctable valgus osteoarthritis of the knee up to 10 degrees of malalignment. CONTRAINDICATIONS: Severe, contract varus osteoarthritis of the knee, severe and moderate, contract valgus osteoarthritis of the knee, severe obesity, exceptionally muscular patients, decreased skin perfusion. SURGICAL TECHNIQUE: Central skin incision from the superior pole of the patella to the tibial tubercle. Exposure of the medial retinaculum and mobilization of the vastus medialis muscle subcutaneously. Incision of the medial retinaculum and blunt separation of the vastus medialis muscle from the intermuscular septum. Lateralization of the patella and flexion of the knee joint. Resection of the tibia perpendicular to the diaphysis. Adjustment of the anteroposterior (AP) resection block at the level of the anterior femoral cortex and of rotation by applying equal tension to the collateral ligaments. Balancing of soft-tissue tension in flexion gap by release, if necessary. After AP resection fixation of distal resection block in planned valgus angle. Balancing of soft-tissue tension in extension gap by release, if necessary. After distal femur resection facet resection, adaptation of posterior femoral condyles, and implantation of prosthesis. Check on stability and range of motion. Wound closure. POSTOPERATIVE MANAGEMENT: Full weight bearing from the 1st postoperative day, CPM (continuous passive motion) with up to 90 degrees flexion with peridural anesthesia as tolerated, stair climbing starting on the 7th postoperative day. RESULTS: 100 patients were randomized to total knee replacement via a parapatellar or subvastus approach. Radiologically, there were no differences in operative precision or leg alignment. Patients treated minimally invasively suffered less pain and achieved a higher flexion of 110 degrees versus 95 degrees 6 weeks postoperatively. However, there were two cases of delayed wound healing in this group. The surgical technique is demanding and the operating time is longer. Long-term results are still missing.

ESB Clinical Biomechanics Award 2008: Complete data of total knee replacement loading for level walking and stair climbing measured in vivo with a follow-up of 6-10 months.

BACKGROUND: Detailed information about the loading of the knee joint is required for various investigations in total knee replacement. Up to now, gait analysis plus analytical musculo-skeletal models were used to calculate the forces and moments acting in the knee joint. Currently, all experimental and numerical pre-clinical tests rely on these indirect measurements which have limitations. The validation of these methods requires in vivo data; therefore, the purpose of this study was to provide in vivo loading data of the knee joint. METHODS: A custom-made telemetric tibial tray was used to measure the three forces and three moments acting in the implant. This prosthesis was implanted into two subjects and measurements were obtained for a follow-up of 6 and 10 months, respectively. Subjects performed level walking and going up and down stairs using a self-selected comfortable speed. The subjects' activities were captured simultaneously with the load data on a digital video tape. Customized software enabled the display of all information in one video sequence. FINDINGS: The highest mean values of the peak load components from the two subjects were as follows: during level walking the forces were 276%BW (percent body weight) in axial direction, 21%BW (medio-lateral), and 29%BW (antero-posterior). The moments were 1.8%BW*m in the sagittal plane, 4.3%BW*m (frontal plane) and 1.0%BW*m (transversal plane). During stair climbing the axial force increased to 306%BW, while the shear forces changed only slightly. The sagittal plane moment increased to 2.4%BW*m, while the frontal and transversal plane moments decreased slightly. Stair descending produced the highest forces of 352%BW (axial), 35%BW (medio-lateral), and 36%BW (antero-posterior). The sagittal and frontal plane moments increased to 2.8%BW*m and 4.6%BW*m, respectively, while the transversal plane moment changed only slightly. INTERPRETATION: Using the data obtained, mechanical simulators can be programmed according to realistic load profiles. Furthermore, musculo-skeletal models can be validated, which until now often lacked the ability to predict properly the non-sagittal load values, e.g. varus-valgus and internal-external moments.