Objective: This prospective observational cohort study aimed to set targets for lower limb joint surgery based on the Timed Up and Go test (TUG), an objective functional outcome measure, in patients with established rheumatoid arthritis (RA). Methods: We validated TUG as an outcome measure of lower limb joint surgery and compared it with changes in patient-reported outcomes, including the Health Assessment Questionnaire Disability Index (HAQ-DI) and European Quality of life scale with five dimensions (EQ-5D). Changes in these outcomes were compared by performed surgery and by achievement of the minimal clinically important difference (MCID) for EQ-5D using univariate analysis of variance. Associations between TUG and HAQ remission (HAQ-DI ≤0.5) were determined using logistic regression analysis. Cut-off values of TUG at baseline and 6 months after surgery for HAQ remission were determined using receiver operating characteristic curves. Results: A total of 126 patients were analyzed. Mean age, HAQ-DI, and TUG were 65.4 years, 1.036, and 12.8 seconds, respectively. After surgery, patients showed improvements in TUG as well as HAQ-DI. TUG at 6 months after surgery was significantly associated with HAQ remission (adjusted OR: 0.78; 95% CI: 0.65-0.93). TUG cut-off values at baseline and 6 months after surgery for achieving HAQ remission were 12.1 and 8.8 seconds, respectively. Significant improvements in TUG (∆TUG, 3.7 seconds) were associated with achievement of the MCID for EQ-5D (≥0.05) at 6 months after surgery. Conclusion: Timed Up and Go test is a useful tool for assessing the outcome of lower limb joint surgery in RA patients. We propose that TUG ≤9 seconds could be an objective target for achieving good physical function after lower limb joint surgery.
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