Autologous Chondrocyte Implantation in Chondral Defects of the Knee With a Type I/III Collagen Membrane: A Prospective Study With a 3-Year Follow-up

Purpose: The clinical results after autologous chondrocyte implantation (ACI) with a collagen membrane using sequential objective patient evaluation (clinical examination and magnetic resonance imaging [MRI]) are inadequately reported. This prospective study was performed to determine the results after ACI at different time intervals over a period of 36 months. Methods: Between 2000 and 2002, 63 patients (mean age, 34 years) with full-thickness chondral lesions of the knee underwent an autologous chondrocyte implantation and were evaluated preoperatively and at 6, 18, and 36 months after surgery. The chondrocyte suspension within the defect was covered with a type I/III collagen membrane. Depending on the localization of the defects (femoral condyles, trochlea, and retropatellar), the patients were assigned to three different groups. Exclusion criteria were meniscal pathologies, axial malpositioning, and ligament instabilities. Baseline clinical scores (modified Cincinnati knee score and the International Cartilage Repair Society score) were determined and compared with follow-up data by using the paired Wilcoxon test. Results: The ICRS and modified Cincinnati score showed significant improvement (P < .01) in all time intervals between preoperative and 6, 18, and 36 months after surgery. There was no significant difference in the final outcome between different defect localizations (P > .2). The Pearson coefficient of correlation between clinical and MRI scores was 0.73 and significant at the 0.01 level. There was no patient with a symptomatic graft hypertrophy. Conclusions: ACI is an effective method in the treatment of isolated cartilage defects in the knee. Graft hypertrophy can be avoided by using a collagen membrane. Significant improvement (P < .001) occurs still between 18 and 36 months after surgery. Level of Evidence: Level IV, therapeutic case series.