PREOPERATIVE PAIN SENSITIVITY HAS A GREATER IMPACT ON CLINICAL OUTCOMES THAN CORONAL ALIGNMENT STRATEGY IN ROBOTIC-ASSISTED TOTAL KNEE ARTHROPLASTY: IMPLICATIONS FOR TRIAL DESIGN

Abstract

Both pre-operative pain sensitivity and coronal alignment philosophy may influence patient-reported outcomes (PROMs) after total knee arthroplasty (TKA). This study investigated whether pain sensitivity predicts function in robotic-assisted TKAs 19andomized to functional alignment (FA) or mechanical alignment (MA), and whether high pain sensitivity obscures differences between strategies. We 19andomizedandomized19d pain sensitivity would be a stronger determinant of outcome than alignment. This sub-study analysed data from a prospective, single-blinded 19andomized controlled trial. A total of 244 patients were allocated to FA (n = 123) or MA (n = 121). Pain sensitivity was assessed pre-operatively using the Pain Sensitivity Questionnaire (PSQ). PROMs – the Forgotten Joint Score (FJS) and Oxford Knee Score (OKS) – were collected two years post-operatively. Multivariable stepwise regression evaluated the influence of PSQ, demographic, and radiographic factors on PROMs. Patients were stratified into high (PSQ ≥ 5.2) and low (PSQ < 5.2) pain sensitivity groups, and FA and MA outcomes compared. Baseline PSQ did not differ between FA and MA groups (5.7 ± 1.9 vs 5.6 ± 1.8; p = 0.58). PSQ was an independent negative predictor of both FJS and OKS (p < 0.01), whereas alignment strategy was not. Among low pain sensitivity patients, FA yielded a higher FJS than MA (74.9 ± 25.8 vs 61.9 ± 31.4; p = 0.03). In high pain sensitivity patients, FJS did not differ (FA 66.8 ± 25.0 vs MA 65.8 ± 29.5; p = 0.80). Pre-operative pain sensitivity exerted a stronger influence on two-year functional outcomes than coronal alignment strategy in robotic-assisted TKA. Alignment philosophy had no discernible effect on outcomes in patients with high pain sensitivity, whereas patients with low pain sensitivity showed higher FJS with FA than with MA. These findings highlight the importance of accounting for patient-related sensory and psychological factors when interpreting PROMs and designing prospective trials evaluating surgical techniques in TKA.