Matrix-associated ACI employing the CaReS technology for the treatment of chondral or osteochondral defects of the knee is a safe and clinically effective treatment that yields significant functional improvement and improvement in pain level. However, further investigation is necessary to determine the long-term viability and clinical outcome of this procedure.

Background: Autologous chondrocyte implantation (ACI) is an established method for treating cartilage defects in the knee of adult patients. However, less is known about its effectiveness in adolescents. Hypothesis: Third-generation matrix-associated ACI (MACI) using spheroids (co.don chondrosphere/Spherox) is an effective and safe treatment for articular cartilage defects in adolescents aged 15 to 17 years, with outcomes comparable with those for young adults aged 18 to 34 years. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 71 patients (29 adolescents, 42 young adults) who had undergone ACI using spheroids were evaluated retrospectively in this multicenter study. For adolescents, the mean defect size was 4.6 ± 2.4 cm 2 , and the follow-up range was 3.5 to 8.0 years (mean, 63.3 months). For young adults, the mean defect size was 4.7 ± 1.2 cm 2 , and the follow-up range was 3.8 to 4.3 years (mean, 48.4 months). At the follow-up assessment, outcomes were assessed by using validated questionnaires (Knee injury and Osteoarthritis Outcome Score [KOOS], International Knee Documentation Committee [IKDC] subjective knee evaluation form and current health assessment form, and modified Lysholm score), the magnetic resonance observation of cartilage repair tissue (MOCART) score, and if relevant, time to treatment failure. Safety was assessed by the treatment failure rate. Results: No significant difference between the 2 study groups was found for KOOS, IKDC, or MOCART scores, with all patients achieving high functional values. A significant difference was found in the modified Lysholm score, favoring the young adult group over the adolescent group (22.3 ± 1.9 vs 21.0 ± 2.4, respectively; P = .0123). There were no differences between the rates of treatment failure, with 3% in the adolescent group and 5% in the young adult group. Conclusion: Third-generation MACI using spheroids is a safe and effective treatment for large cartilage defects of the knee in adolescents at midterm follow-up. Outcomes are comparable with those for young adults after ACI.

Background High tibial osteotomy (HTO) for varus deformities is a common concomitant treatment in cartilage surgery. Aim of the present study was to analyze factors influencing the decision towards accompanying HTO in patients with cartilage defects of the medial femoral condyle, such as the amount of varus deformity. Methods Data from 4986 patients treated for cartilage defects of the knee from the German Cartilage Registry (KnorpelRegister DGOU) were used for the current analysis. Seven hundred and thirty-six patients fulfilled the inclusion criteria. Their data were analyzed for factors influencing the decision towards performing a concomitant HTO using t test, univariate and multivariate binary logistic regression models. Results The break point at which the majority of patients receive a concomitant HTO is 3° of varus deformity. Several factors apart from the amount of varus deformity (5.61 ± 2.73° vs. 1.72 ± 2.38°, p < 0.00) differed significantly between the group of patients with HTO and those without. These included defect size (441.6 ± 225.3 mm2 vs. 386.5 ± 204.2 mm2, p = 0.001), symptom duration (29.53 ± 44.58 months vs. 21.85 ± 34.17 months, p = 0.021), defect grade (62.5% IVa/IVb vs. 57.3% IVa/IVb, p = 0.014), integrity of corresponding joint surface (10.8% grade III–IV vs. 0.2% grade III–IV, p < 0.001), meniscus status (15.5% > 1/3 resected vs. 4.4% > 1/3 resected, p < 0.001) and number of previous surgeries (1.01 ± 1.06 vs. 0.75 ± 1.00, p = 0.001). In the stepwise multivariate binary logistic regression test, only the amount of varus deformity, symptom duration and quality of the corresponding joint surface remained significant predictors associated with performing a concomitant HTO. Conclusion Based upon data from a nationwide cohort, additional HTO in context with cartilage repair procedures of the medial femoral condyle is frequently performed even in mild varus deformities less than 5°. Other factors also seem to influence decision for HTO.

The goal was to examine gender differences of patient characteristics and outcome after cartilage repair based on a collective of nearly 5,000 patients. Patient characteristics, accompanying therapies, and outcome (Knee Injury and Osteoarthritis Outcome Score [KOOS], reoperations, patient satisfaction) of 4,986 patients of the German cartilage register DGOU were assessed by t test for possible gender differences. P values <0.05 were considered statistically significant. Women were older than men (38.07 ± 12.54 vs. 26.94 ± 12.394 years, P = 0.002), more often preoperated (0.30 ± 0.63 vs. 0.24 ± 0.55, P = 0.001), and had a longer symptom duration (25.22 ± 41.20 vs. 20.67 ± 35.32 months, P < 0.001). Men had greater mean leg axis malalignment than women (3.24° ± 3.26° vs. 2.67° ± 3.06°, P < 0.001), less favorable meniscal status ( P = 0.001), worse defect stage ( P = 0.006), and a more severely damaged corresponding articular surface ( P = 0.042). At baseline (59.84 ± 17.49 vs. 52.10 ± 17.77, P < 0.001), after 6 months (72.83 ± 15.56 vs. 66.56 ± 17.66, P < 0.001), after 12 months (77.88 ± 15.95 vs. 73.07 ± 18.12, P < 0.001), and after 24 months (79.311 ± 15.94 vs. 74.39 ± 18.81, P < 0.001), men had better absolute KOOS values, but women had better relative KOOS increases 6 months (14.59 ± 17.31 vs. 12.49 ± 16.3, P = 0.005) as well as 12 months postoperatively (20.27 ± 18.6 vs. 17.34 ± 17.79, P = 0.001) compared with preoperatively, although 12 and 24 months postoperatively they were subjectively less satisfied with the outcome ( P < 0.001) and had a higher reintervention rate at 24 months (0.17 ± 0.38 vs. 0.12 ± 0.33, P = 0.008). In summary, the present work shows specific gender differences in terms of patient characteristics, defect etiology, defect localization, concomitant therapy, and the choice of cartilage repair procedure. Unexpectedly, contrary to the established scientific opinion, it could be demonstrated that women show relatively better postoperative KOOS increases, despite a higher revision rate and higher subjective dissatisfaction.

Total knee replacement requires exact implantation in order to avoid long-term failure. Longitudinal in vivo studies of malaligned prostheses are problematic for ethical reasons. To assess the critical angle of tibial (varus/valgus) malalignment of knee prostheses in vitro, a simulator investigation was performed. Mobile-bearing prostheses were implanted in a simulator with 1-3 degrees valgus and varus malalignment as well as in a neutral position. More extreme malalignment caused unacceptable forces in the simulator. After each 500,000 cycles (ca. 0.5 years of walking) the replicas of the polyethylene inlay were examined and the extent of the tribocontact areas was measured until 1,500,000 total cycles. Finally the original polyethylene was examined with a scanning electron microscope. The polyethylene showed only abrasive wear without any fatigue effect. Tribocontact areas of 900-1500 mm(2) were observed under malalignment of mobile-bearing prostheses according to the manufacturer's specifications. With 1-3 degrees of malalignment, tribocontact areas were located at atypical polyethylene zones, but still showed abrasive wear only. Increasing malalignment due to a lift off of the femoral part of the prostheses with a strong torsional strength of the polyethylene made more extreme simulation impossible. Malalignment of 3 degrees could be suggested as maximum in vivo tolerability; perfect alignment with ideal implantation should be the goal. Soft tissue was given less consideration in this simulator study.