Purpose

To evaluate autologous matrix-induced chondrogenesis (AMIC) for isolated focal retropatellar cartilage lesions and the influence of patellofemoral (PF) anatomy on clinical outcomes at a minimum of 2-year follow-up.

Methods

Twenty-nine consecutive patients (31 knees) that underwent retropatellar AMIC with a mean age of 27.9 +/- 11.0 years were evaluated at a follow-up averaging 4.1 +/- 1.9 (range, 2 to 8) years. Patient factors, lesion morphology and patient-reported outcome measures including KOOS, Tegner, Kujula score and VAS score were collected. PF anatomy was assessed on pre- and postoperative imaging, and subsequently correlated to outcome scores and failure to determine risk factors for poor outcome.

Results

At final follow-up, the AMIC graft failed in 4 cases (12.9%) at a mean follow-up of 21 +/- 14.1 months. Patients with failed grafts had a significantly smaller patellar and Laurins' PF angle than patients whose graft did not fail (p=0.008 and p=0.004, respectively). Concomitant corrective surgery for patellar instability was performed in 29 knees (93.5%). Grafts that did not fail presented with an average Kujala score of 71.3 +/-16.9, KOOS of 68.7 and Tegner scores of 4.2 +/- 1.8. The patellar angle was significantly associated with the patient’s satisfaction level (r=0.615; p<0.001).

Conclusion

AMIC for retropatellar cartilage lesions in combination with concomitant corrective surgery for patellar instability results in low failure rate with satisfactory clinical outcome and patient satisfaction of almost 80% at mid-term follow-up. Smaller patellar and Laurins' PF angle are associated with less favorable outcome.