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