The accessory tendon of extensor hallucis longus muscle and its correlation to hallux valgus deformity: a cadaveric study

The accessory tendon (AT) of the extensor hallucis longus (EHL) is a common anatomic variation, whose clinical significance remains debatable. The purpose of this study was to investigate the incidence and morphology of accessory EHL tendons in cadavers and to examine any possible correlation to the occurrence and severity of hallux valgus (HV) deformity. We examined any possible correlation between the AT presence and the cadavers' age and the HV deformity in 98 female adult cadaveric feet. The HV and intermetatarsal (IMA) angles were measured and compared with the relative angle between the primary EHL tendon and AT as well as the length of the AT. AT was present in 26.5% and HV deformity existed in 36.7% of all feet. There was a high prevalence (65.4%) of HV deformity in feet with AT, but the HV angle and IMA were similar in feet with AT and without AT. No significant correlations were found between AT morphological characteristics and the cadavers' age or the HV angle and IMA. In conclusion, there is a high incidence of HV deformity in cadaveric feet with AT of EHL (almost 2/3), but there is no correlation between the severity of the HV deformity and the presence or characteristics of the AT.