Characterized Chondrocyte Implantation in the Patellofemoral Joint An Up to 4-Year Follow-up of a Prospective Cohort of 38 Patients

Background: Autologous chondrocyte implantation (ACI) is an accepted treatment option for selected condylar cartilage defects in the knee. Results for patellofemoral chondral defects have been less favorable. Hypothesis: Autologous chondrocyte implantation with characterized chondrocytes will result in clinically relevant improvement in patellofemoral lesions. Study Design: Case series; Level of evidence, 4. Methods: Patients with symptomatic patellofemoral full-thickness cartilage lesions were treated with ACI using characterized chondrocytes (ChondroCelect) covered with a collagen type I membrane. Clinical outcome was assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and a visual analog scale (VAS) for pain. Responders were defined using 5 categories (>= 10 points and >= 20%, 30%, 50%, 70%) based on the KOOS and VAS. Treatment failure was defined as partial loosening of more than 20% of the graft with subsequent procedures to the subchondral bone. Results: Thirty-eight patients, with a mean defect size of 4.89 cm(2) (range, 1.5-11 cm(2)), were treated for a patellar defect (n = 28), trochlear defect (n = 7), or a kissing lesion (trochlea and patella; n = 3). The minimum follow-up period was 24 months (mean, 37 months; range, 24-72 months). Treated patients showed statistically significant improvements in the KOOS (at 12, 18, 24, 36, and 48 months) and VAS (at the same time points) compared with pretreatment for each time point. Responder analysis identified approximately 84% of patients with a clinically relevant improvement greater than 10 points at 3 years. Treatment failure was observed in 5 patients. The most commonly reported adverse events were joint crepitation (n = 18) and arthrofibrosis (n = 7). No relationship could be found between clinical outcome and anatomic characteristics of the patellofemoral joint, lesion size and site, time since onset, or age. Nine patients required additional surgery: 6 because of persistent symptoms and 3 for hardware removal. Conclusion: Characterized chondrocyte implantation resulted in statistically significant and clinically relevant improvement over time. These results add to the evidence demonstrating that ACI is a valuable cartilage repair technique for patellofemoral lesions.