Step Activity After Surgical Treatment of Ankle Arthritis

Abstract

Category: Ankle Arthritis Introduction/Purpose: We used step counts as objective measures of activity as a compliment to patient self-reported outcomes in treatment of ankle arthritis to validate success or failure of treatment. Methods: 234 patients who were treated with ankle arthrodesis or ankle replacement wore step activity monitors before treatment and after treatment at 6 months, 12 months, 24 months and 36 months. Total steps taken as well as low, medium and high activity, sustained activity, and an activity index were measured in each group. In addition, step activity was compared with the subjects’ self-reported outcome using the MFA and SF-36. We measured change from baseline and compared treatment type. Linear mixed-effects regression analysis was used to test for improvement in step activity (the dependent variables) across follow-up (the fixed effect, modeled as 4 dummy variables representing differences from pre-op at 6, 12, 24 and 36 months), with fixed covariates age, sex, body mass index (BMI) and surgical treatment. Results: Both treatment groups improved significantly. Objective and PROM were not parallel. While PROM plateaued at 6 months, steps continued to increase at 36 months. Step counts increases did correlate with improving PROM however. Patients undergoing arthrodesis had slower improvement than arthroplasty patients with greater differences in the early stages of recovery (i.e., 6 and 12-month post-op) than at 36 months where improvements were similar across groups. (See table 2 for data). The trajectory of recovery was different but there were no significant differences in improvement by surgery procedure. Conclusion: Patients increase the number and the intensity of steps after treatment. Improvement after arthrodesis and ankle replacement follow different trajectories. For step totals, high intensity steps and the sustained activity metrics, arthroplasty patients showed more improvement than arthrodesis patients early in recovery. Step data are consistent with patient reported outcomes but do not parallel them. Unlike PROM which improve dramatically in the first six months then plateau, step activity demonstrated mild or no improvement at 6 months but later had improvement that increased gradually across follow-up out to three years. Objective outcome measures add value to measurement of treatment outcomes.