A two to fifteen year follow-up case series of ninety one patients after onlay patellofemoral arthroplasty highlighting the impact of preoperative symptoms and mental health

Patellofemoral osteoarthritis (PFOA) substantially impairs quality of life, and isolated patellofemoral arthroplasty (PFA) is a surgical option for therapy-refractory symptoms. This study evaluated the clinical and functional outcomes and survivorship of an onlay PFA implant, hypothesizing favourable results in the mid- to long-term follow-up. Between 2009 and 2023, 128 knees (123 patients) with PFOA underwent onlay PFA (Journey™ PFJ, Smith & Nephew) and were retrospectively analyzed. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the Short Form-12 (SF-12) and the numerical analog scale (NAS) for pain and function were assessed preoperatively and at the final follow-up. Postoperative complications and revisions were recorded. Follow-up data were available for 91 knees (88 patients; mean age 60.7 ± 10.3 years) over 6.1 ± 3.4 years. Significant improvements in the WOMAC total score (57.3% to 22.5%; p < 0.001), SF-12 physical (29.6 to 43.5; p < 0.001) and mental scores (46.8 to 52.7; p < 0.001), and NAS function (4.7 to 7.2; p < 0.001) and pain (7.8 to 3.1; p < 0.001) were observed. Patients who did not achieve the minimal clinically important difference (MCID) had higher preoperative WOMAC scores (61.3% vs. 46.0%; p = 0.018). The SF-12 mental component summary (MCS) scores was correlated with the pre- and postoperative WOMAC scores (r2 = 0.21–0.32; p ≤ 0.002). Kaplan–Meier analysis revealed PFA survivorship rates of 89%, 75%, and 67% at five, ten and 15 years, respectively. Onlay PFA provides significant and sustained improvements in pain, function, and quality of life in patients with PFOA, with satisfactory mid- to long-term implant survivorship. A low preoperative WOMAC score and poor mental health, as indicated by the SF-12 MCS, may be associated with less favourable postoperative outcomes.