Characteristics of the accessory tendon of the extensor hallucis longus muscle: a Taiwanese study

Purpose The main tendon of the extensor hallucis longus (EHL) muscle attaches to the dorsal aspect of the distal phalanx of the great toe. One or multiple accessory tendons of the EHL have been reported in several ethnic/regional groups, except Taiwan. This study aimed to investigate the incidence, length, and insertion of the accessory tendon of the EHL in Taiwanese people. Methods Anatomical dissection was performed on 48 feet of 24 formalin-embalmed cadavers. The occurrence and morphological characteristics of the accessory tendon of the EHL were recorded and analyzed. Results The accessory tendon of the EHL was found in 97.92% (47/48) of the legs that were dissected. In one male cadaver, an independent muscle belly was identified in each leg, whereas all the other accessory tendons originated from the main tendon of the EHL. In this study, the insertion of the accessory tendon were classified into four patterns. The most common insertion sites were the first metatarsophalangeal (MTP) joint capsule and proximal phalanx of the great toe. The length of the accessory tendons did not correlate with age or with sex when the two tendons with independent muscle belly were excluded. Conclusions The accessory tendon of the EHL appears to be a regular feature in Taiwanese people. Most accessory tendons of the EHL (85.7%) attached on the first MTP joint capsule may play a role in the prevention of capsular impingement during great toe extension.