An ankle-foot orthosis with a lateral extension reduces forefoot abduction in subjects with stage II posterior Tibial tendon dysfunction

STUDY DESIGN: Controlled laboratory, repeated measures. BACKGROUND: Posterior tibial tendon dysfunction is a common musculoskeletal problem that includes tendon degeneration and collapse of the medial arch of the foot (flatfoot deformity). Anklefoot orthoses (AFOs) typically are used to correct flatfoot deformity. Correction of flatfoot deformity involves increasing forefoot adduction, forefoot plantar flexion, and hindfoot inversion. OBJECTIVES: To test whether a foot orthosis with a lateral extension reduces forefoot abduction in patients with stage II posterior tibial tendon dysfunction while walking. METHODS: The gait of 15 participants with stage II posterior tibial tendon dysfunction was evaluated under 3 conditions: A standard AFO, an AFO with a lateral extension, and a shoe-only control condition. Kinematic variables of interest were evaluated at designated time points in the gait cycle and included hindfoot inversion/eversion, forefoot plantar flexion/dorsiflexion, and forefoot abduction/adduction. A 3-by-4, repeatedmeasures analysis of variance (brace condition by gait phase) was used to compare variables across conditions. RESULTS: The AFO with a lateral extension resulted in a significantly greater change in forefoot adduction compared to the standard AFO (2.6°, P = .02) and shoe-only conditions (4.1°, P<.01) across all phases of stance. Forefoot plantar flexion was significantly increased when comparing the standard AFO and AFO with a lateral extension to the shoe-only condition. The AFO with the lateral extension also demonstrated significantly increased hindfoot inversion during the loading response and terminal stance phases. CONCLUSION: Off-the-shelf and standard AFOs have been shown to improve forefoot plantar flexion and hindfoot eversion, but not forefoot adduction. A lateral extension added to a standard AFO along the forefoot significantly improved forefoot adduction in participants with posterior tibial tendon dysfunction while walking.