Treatment of Large Cartilage Defects in the Knee by Hydrogel-Based Autologous Chondrocyte Implantation: Two-Year Results of a Prospective, Multicenter, Single-Arm Phase III Trial

Objective To evaluate the clinical outcome of a hydrogel-based autologous chondrocyte implantation (ACI) for large articular cartilage defects in the knee joint. Design Prospective, multicenter, single-arm, phase III clinical trial. ACI was performed in 100 patients with focal full-thickness cartilage defects ranging from 4 to 12 cm(2) in size. The primary outcome measure was the responder rate at 2 years using the Knee Injury and Osteoarthritis Outcome Score (KOOS). Results Two years after ACI treatment, 93% of patients were KOOS responders having improved by >= 10 points compared with their pre-operative level. The primary endpoint of the study was met and demonstrated that the KOOS response rate is markedly greater than 40% with a lower 95% CI (confidence interval) of 86.1, more than twice the pre-specified no-effect level. KOOS improvement (least squares mean) was 42.0 +/- 1.8 points (95% CI between 38.4 and 45.7). Mean changes from baseline were significant in the overall KOOS and in all 5 KOOS subscores from Month 3 (first measurement) to Month 24 (inclusive) (P < 0.0001). The mean MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) score after 24 months reached 80.0 points (95% CI: 70.0-90.0 points) and 92.1 points in lesions <= 5 cm(2). Conclusions Overall, hydrogel-based ACI proved to be a valuable treatment option for patients with large cartilage defects in the knee as demonstrated by early, statistically significant, and clinically meaningful improvement up to 2 years follow-up. Parallel to the clinical improvements, MRI analyses suggested increasing maturation, re-organization, and integration of the repair tissue.