Muscular imbalances resulting in a clawed hallux

Abstract

A clawed hallux is a deformity of the great toe resulting from a muscular imbalance. Using a cadaveric foot-loading frame, we quantitatively assessed the role of the peroneus longus (PL), extensor hallucis longus (EHL), and flexor hallucis longus (FHL) on position and pressure distribution of the first ray by simulating muscle imbalances. The experimental protocol included applying seven different combinations of simulated disproportionate loads ("overpulls") for these three muscles using midstance force values derived from the literature. This study quantified the angular change in the joints of the first ray and measured the plantar pressure beneath the head of the first metatarsal and the hallux. The results indicated that the peroneus longus was statistically the greatest contributor to the elevation of plantar pressure beneath the first metatarsal, while the EHL and FHL were primarily responsible for the angular changes resulting in the clawed hallux deformity.