Purpose: To prospectively evaluate the clinical and radiographic outcomes and survivorship at 2 and 5 years after isolated contemporary patellofemoral inlay arthroplasty.
Methods: Thirty-four patients were prospectively enrolled in the study and were evaluated preoperatively and at 2 and 5 years postoperatively. Clinical outcomes included the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score and the visual analogue scale (VAS) for pain. Kellgren-Lawrence grading was used to assess the progression of tibiofemoral osteoarthritis and the Caton-Deschamps Index to determine patellar height. A Kaplan-Meier survival analysis was used to investigate the implant survivorship. Preoperative patient characteristics were compared among failures and success to determine potential risk factors and patient satisfaction was rated postoperatively.
Results: Five of the 34 patients were lost to follow-up resulting in a final follow-up rate of 86%. The total WOMAC subscores of pain and function and the VAS Pain improved significantly at 2- and 5-years, with no significant difference between the two time points. The WOMAC stiffness subscale reached significant improvement at 2-year follow-up alone. No significant progressions of tibiofemoral arthritis or changes in patellar height were observed. A total of six patients (17.1%) failed leaving a survival rate of 91% after 2 years and 83% after 5 years. The main cause for postoperative failure was persistent knee pain; however, no significant preoperative risk factor in patient characteristics could be identified.
Conclusion: Patellofemoral inlay arthroplasty shows high patient satisfaction with significant improvement in knee function and pain relief after mid-term follow-up with no radiographic progression of tibiofemoral OA.
Level of evidence: Prospective case series, Level III.
Keywords: Inlay; Knee; Patellofemoral; Patellofemoral arthroplasty; Patellofemoral osteoarthritis; Patellofemoral resurfacing; Retropatellar resurfacing; Trochlea; WAVE prosthesis.