AMIC achieves sustained clinical improvement in isolated patellar cartilage defects over 5 years, correlating with MRI

Purpose: To evaluate 5-year postoperative clinical outcomes of autologous matrix-induced chondrogenesis (AMIC) for isolated ICRS grade 3-4 patellar cartilage defects and correlate outcomes with magnetic resonance imaging (MRI). The hypothesis was that AMIC would improve clinical symptoms and induce neocartilage formation, visible on MRI, making it a safe and effective option for repairing focal patellar cartilage defects. Methods: The cohort comprised 13 focal patellar lesions in 12 patients. Pain visual analogue scale (VAS), Knee Injury and Osteoarthritis Outcome Score (KOOS), Kujala score, EuroQol-5D Health Survey questionnaire and MRI data were assessed preoperatively and at 2 and 5 years postoperatively. All MRI scans were evaluated using the Magnetic Resonance Observation of Cartilage Repair Tissue System. Descriptive statistics were calculated on all data. Inferential analysis comparing outcome scores before and after surgery employed the nonparametric Wilcoxon signed-rank test, with the nonparametric Friedman test used to detect differences across multiple test attempts. p < 0.05 was considered statistically significant. Results: Twelve patients (23-52 years old) with patellofemoral chondral full-thickness defects (2-4 cm) were treated. At a 5-year follow-up, eleven knees showed MRI improvement. Two were asymptomatic and nine showed clear clinical improvement. Only one knee showed no clinical improvement. MRI revealed a defect filling with newly formed cartilage characterized by a less compact and heterogeneous signal. Cartilage degradation or joint damage was observed in two knees, and bone formation within the plate was identified in four. AMIC significantly improved patients' VAS pain, KOOS, EuroQol-5D and Kujala scores compared to preoperative baseline for up to 5 years postoperatively. Conclusions: Satisfactory clinical outcomes and new cartilage formation, as observed by MRI, are achieved with AMIC at mid-term follow-up for ICRS grade 3-4 in small-to-medium-sized patellar defects in patients under 52 years of age, with improvements maintained for up to 5 years. Level of Evidence: Level III.