A Dynamic Ankle Orthosis Reduces Tibial Compressive Force and Increases Ankle Motion Compared With a Walking Boot

Abstract

Purpose: Tibial bone stress injuries are a common overuse injury among runners and military cadets. Current treatment involves wearing an orthopedic walking boot for 3 to 12 wk, which limits ankle motion and leads to lower limb muscle atrophy. A dynamic ankle orthosis (DAO) was designed to provide a distractive force that offloads in-shoe vertical force and retains sagittal ankle motion during walking. It remains unclear how tibial compressive force is altered by the DAO. This study compared tibial compressive force and ankle motion during walking between the DAO and an orthopedic walking boot. Methods: Twenty young adults walked on an instrumented treadmill at 1.0 m•s −1 in two brace conditions: DAO and walking boot. Three-dimensional kinematic, ground reaction forces, and in-shoe vertical force data were collected to calculate peak tibial compressive force. Paired t-tests and Cohen's d effect sizes were used to assess mean differences between conditions. Results: Peak tibial compressive force (P = 0.023; d = 0.5) and Achilles tendon force (P = 0.017; d = 0.5) were moderately lower in the DAO compared with the walking boot. Sagittal ankle excursion was 54.9% greater in the DAO compared with the walking boot (P = 0.05; d = 3.1). Conclusions: The findings from this study indicated that the DAO moderately reduced tibial compressive force and Achilles tendon force and allowed more sagittal ankle excursion during treadmill walking compared with an orthopedic walking boot.