0463 - Changes in Subtalar Joint Moment Arms following Split Tendon Transfers of Tibialis Anterior and Tibialis Posterior

INTRODUCTION Split tendon transfers of tibialis anterior (TA) or tibialis posterior (TP) are commonly performed to correct varus deformity of the hindfoot in patients with cerebral palsy, stroke, and brain injury. Both of these procedures involve detaching half of the tendon from its medial insertion and reattaching laterally such that the muscle acts as a balanced yoke that neither inverts nor everts the foot [1,2]. Clinical results for these procedures have been generally good but highly variable; some surgical failures have been attributed to difficulties in achieving a proper balance of tension between the tendon halves [2]. The effect of variation of the lateral insertion site of TA was investigated in a previous cadaver study, but changes in muscle moment arms resulting from the procedure were not measured [3]. Knowledge of subtalar joint moment arms is important for understanding how the inverting action of the muscle is changed following surgery, and how its function depends on joint angle. The goal of the present study was to measure subtalar joint moment arms of TA and TP before and after split tendon transfer.