The effects of total ankle replacement on ankle joint mechanics during walking

BACKGROUND: End-stage ankle arthritis impairs joint function and patients' mobility. Total ankle replacement is a surgical procedure to treat severe ankle arthritis. Salto Talaris Anatomic Ankle(TM) (STAA) was designed to mimic the normal ankle anatomy and flexion/extension of the ankle movement. The purpose of this study was to examine the effect of an STAA ankle replacement on ankle joint function and mechanics during gait. METHODS: Five patients with end-stage unilateral ankle arthritis were recruited. Patients performed level walking in a laboratory setting on 2 occasions, prior to and 3 months after the STAA ankle surgeries. American Orthopedic Foot and Ankle Society (AOFAS) hindfoot score was obtained. A 12-camera motion capture system was used to perform walking analysis. Gait temporo-spatial parameters and ankle joint mechanics were evaluated. Paired Student's t tests and non-parametric Wilcoxon matched tests were performed to examine the differences in biomechanical variables between the pre- and post-surgery walking conditions. RESULTS: Compared to the pre-surgical condition, at 3 months of post-STAA surgery, patients experienced greater improvement in AOFAS hindfoot score (p = 0.0001); the STAA ankle demonstrated a 31% increase in ankle joint excursion (p = 0.045), a 22% increase in ankle plantarflexor moment (p = 0.075), a 60% increase in ankle power absorption (p = 0.023), and a 68% increase in ankle power production (p = 0.039). Patients also demonstrated a 26% increase in walking speed (p = 0.005), a 20% increase in stride length (p = 0.013), a 15% decrease in double support time (p = 0.043), and a 5% decrease in total stance time (p = 0.055). CONCLUSION: Three months after surgeries, the STAA patients experienced improvements in ankle function and gait parameters. The STAA ankle demonstrated improved ankle mechanics during daily activities such as walking.