Treatment of Symptomatic Cartilage Defects of the Knee: Characterized Chondrocyte Implantation Results in Better Clinical Outcome at 36 Months in a Randomized Trial Compared to Microfracture

Background: Damaged articular cartilage has limited capacity for self-repair. Autologous chondrocyte implantation using a characterized cell therapy product results in significantly better early structural repair as compared with microfracture in patients with symptomatic joint surface defects of the femoral condyles of the knee. Purpose: To evaluate. clinical outcome at 36 months after characterized chondrocyte implantation (CCI) versus microfracture (MF). Study Design: Randomized controlled trial; Level of evidence, 1. Methods: Patients aged 18 to 50 years with single International Cartilage Repair Society (ICRS) grade III/IV symptomatic cartilage defects of the femoral condyles were randomized to CCI (n = 57) or MF (n = 61). Clinical outcome was measured over 36 months by the Knee injury and Osteoarthritis Outcome Score (KOOS). Serial magnetic resonance imaging (MRI) scans were scored using the Magnetic resonance Observation of Cartilage Repair Tissue (MOCART) system and 9 additional items. Gene expression profile scores associated with ectopic cartilage formation were determined by RT-PCR. Results: Baseline mean overall KOOS (+/- SE) was comparable between the CCI and MF groups (56.30 +/- 1.91 vs 59.46 +/- 1.98, respectively). Mean improvement (+/- SE) from baseline to 36 months in overall KOOS was greater in the CCI group than the MF group (21.25 +/- 3.60 vs 15.83 +/- 3.48, respectively), while in a mixed linear model analysis with time as a categorical variable, significant differences favoring CCI were shown in overall KOOS (P = .048) and the subdomains of Pain (P = .044) and QoL (P = .036). More CCI- than MF-treated patients were treatment responders (83% vs 62%, respectively). In patients with symptom onset of <2 years, the mean improvement (+/- SE) from baseline to 36 months in overall KOOS was greater with CCI than MF (24.98 +/- 4.34 vs 16.50 +/- 3.99, respectively) and even greater in patients with symptom onset of <3 years (26.08 +/- 4.10 vs 17.09 +/- 3.77, respectively). Characterized chondrocyte implantation patients with high (>= 2) versus low (<2) gene profile scores showed greater improvement from baseline in mean overall KOOS (+/- SE) at 36 months (28.91 +/- 5.69 vs 18.18 +/- 5.08, respectively). Subchondral bone reaction significantly worsened over time with MF compared with CCI (P < .05). Conclusion: Characterized chondrocyte implantation for the treatment of articular cartilage defects of the femoral condyles of the knee results in significantly better clinical outcome at 36 months in a randomized trial compared with MF Time to treatment and chondrocyte quality were shown to affect outcome.