Patient-reported outcomes, function, and gait mechanics after fixed and mobile-bearing total ankle replacement

Background: The popularity of total ankle replacement as a treatment for end-stage arthritis continues to grow. The purpose of this study was to assess changes in ankle kinetics and kinematics from a preoperative time point through two years postoperatively in patients who had received either a fixed-bearing or a mobile-bearing implant. Methods: Ninety patients who received a primary total ankle replacement (forty-nine mobile-bearing and forty-one fixedbearing) were examined. Three-dimensional joint mechanics and ground reaction forces were measured during level walking preoperatively and one and two years postoperatively. Patient-reported and functional outcomes were also collected. Data were analyzed with use of a 3 × 2 repeated-measures analysis of variance (ANOVA) to determine significant differences between implant types and across time (α = 0.05). Results: No significant difference was observed in the ankle motion or step time between implant types or across time. However, there was a greater increase in the peak plantar flexion moment and the Short Form-36 (SF-36) total score across time in the fixed-bearing group than in the mobile-bearing group. Conversely, visual analog scale (VAS) pain scores exhibited greater improvement in the mobile-bearing group than in the fixed-bearing group. Independent of implant type, a significant improvement was observed in walking speed, results of the functional tests, spatiotemporal variables, patientreported outcomes, and vertical ground reaction forces. Independent of time, the fixed-bearing group demonstrated a significant increase in both the weight-acceptance and the propulsion ground reaction forces compared with the mobilebearing group. The mobile-bearing group completed the Sit-to-Stand test significantly faster. Conclusions: All of the observed changes suggest improved or maintenance of function following total ankle replacement. In general, the group with a fixed-bearing implant demonstrated improvements in ankle moment and ground reaction forces, while the mobile-bearing-implant group demonstrated improvements in patient-reported pain outcome. There were few significant changes between the two implant types. Level of Evidence: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.