Patellofemoral osteoarthritis in patients with operative treatment for patellar dislocation: a magnetic resonance-based analysis.

Purpose: the clinical role of patellofemoral (PF) osteoarthrosis (OA) in the outcome after PF stabilizing surgery is poorly understood. The study hypothesis was that PF cartilage lesions and OA are associated with a poor long-term outcome after PF stabilizing surgery.

Methods: the study cohort included thirty-seven patients who underwent PF stabilizing surgery by traditional nonanatomic procedures and were evaluated a minimum of 10 years (range 10-21) after surgery. PF OA was assessed by magnetic resonance (MR) images and plain radiographs obtained at follow-up. Median patient age at follow-up was 33 years (29-43).

Results: at the final follow-up, PF full-thickness cartilage lesions were observed on MR images in 29 (78%) patients. Only 46% of the patients reported satisfaction at follow-up, and dissatisfaction was associated with PF OA (full-thickness articular cartilage loss on MR images; P = 0.022). Especially high incidence, 89%, of medial patellar facet cartilage lesions were found among the patients dissatisfied with the result (16/18 patients) (n.s.). Eight (22%) of the 37 patients reported recurrent patellar instability episodes at follow-up. Median Kujala score was 83 points (range 55-98).

Conclusion: patellofemoral OA is a significant long-term risk of nonanatomic surgery for patellar instability and has a greater impact on subjective outcome than residual instability more than 10 years after surgery.