Impact of Wiberg patellar morphology on patient-reported outcomes following unicompartmental knee arthroplasty: A 3 ~ 5 year retrospective cohort analysis

While unicompartmental knee arthroplasty (UKA) effectively treats medial compartment osteoarthritis, patient-reported outcomes remain variable. The patellofemoral joint is a recognized source of persistent symptoms, yet the influence of specific patellar morphologies, as classified by the Wiberg system, on functional recovery and satisfaction is not well defined. This study aimed to evaluate the impact of Wiberg patellar types on patient-reported outcomes following UKA. In this retrospective cohort study, 327 consecutive patients who underwent fixed-bearing UKA between 2020 and 2023 were categorized by Wiberg type: 59 Type I, 200 Type II, and 68 Type III. Preoperative and postoperative outcomes were assessed using the Forgotten Joint Score-12 (FJS-12), Feller score (and its components: anterior knee pain, stair-climbing, sit-to-stand), Hospital for Special Surgery (HSS) score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and patient satisfaction. Although all groups showed significant improvement in knee function postoperatively, distinct intergroup disparities emerged. A significant main effect of patellar type was observed for FJS-12 (F = 17.827, p < 0.001, η²=0.099) and Feller scores (F = 16.585, p < 0.001, η²=0.093). Post-hoc analysis revealed that patients with Type III patellae reported significantly inferior FJS-12 scores compared to Type II (mean difference: -6.36 points, 95% CI [-8.92, -3.80], p < 0.001) and greater anterior knee pain. Consequently, the Type III group exhibited a significantly higher dissatisfaction rate (13.2%) versus the Type II group (3.5%; p < 0.0125). No significant differences were found in HSS, WOMAC or baseline demographics among the groups. UKA provides significant functional improvement across all Wiberg patellar types. However, patients with Wiberg Type III morphology reported consistently inferior patient-reported outcomes and lower satisfaction. This strong association highlights the clinical importance of preoperative identification of Type III patella, as these patients may benefit from tailored surgical planning and specific postoperative rehabilitation protocols to optimize their results.