The Two-Step Test as a Practical Discriminator of Independent Ambulation One Week After Total Hip Arthroplasty

Background This study aimed to identify physical function factors associated with independent ambulation without assistive devices one week after total hip arthroplasty (THA) in female patients. Methodology This retrospective cohort study included 162 female patients who underwent unilateral THA via a posterior approach for hip osteoarthritis between January 2020 and February 2023. Patients were classified into the following two groups based on the locomotion item of the Functional Independence Measure: the independent ambulation group (n = 92) and the dependent ambulation group (n = 70). Physical function was assessed one week postoperatively using knee extension strength, hip abduction strength, the 30-second chair stand test, the two-step test, and one-leg stance time. Results The independent ambulation group showed significantly better performance in all physical function measures, except knee extension strength on the operated side. Multivariate logistic regression identified the two-step value as the only independent factor associated with independent ambulation (odds ratio = 0.02; 95% confidence interval = 0.00-0.10; p < 0.001). The optimal cut-off value was 0.331, with an area under the curve of 0.87, a sensitivity of 80.0%, and a specificity of 93.5%. Conclusions The two-step test is a simple and clinically useful tool for identifying patients capable of independent ambulation without assistive devices in the early postoperative period after THA. A two-step value of 0.331 may serve as an objective indicator to support early rehabilitation planning. Future longitudinal studies are warranted to evaluate the relationship between early two-step test performance and long-term functional recovery after THA.