Applied anatomy of accessory tendons of extensor hallucis longus muscle and hallux valgus deformity: a cadaveric and radiologic study.

Introduction: The accessory tendon of the extensor hallucis longus (ATEHL) represents a common anatomical variant. However, the role of ATEHL in the etiology of hallux valgus (HV) has not yet been fully elucidated. This study aimed to determine the incidence and morphology of the ATEHL in cadavers and examine its possible correlation with the HV deformity presence and the relevant angular measurements of the feet.

Materials and methods: The study included 63 embalmed cadaveric feet. Following documentation of the demographic parameters of the cadavers, the dorsal aspect of the first ray was carefully dissected. The existence and morphological features of the ATEHL were recorded and analyzed. Subsequently, plain radiographs were taken to assess the hallux valgus angles (HVA) and intermetatarsal angles (IMA) without weight-bearing simulation. In this evaluation, HVA exceeding 15° and IMA exceeding 9° were characterized as hallux valgus (HV) deformity. Statistical analysis was used to examine any correlations between ATEHL existence and HV deformity presence, HVA degrees and IMA degrees.

Results: An ATEHL was found in 37 out of 63 cadaveric feet (58.73 %). A HV deformity was identified in 32 out of 63 cadaveric feet (50.79 %). The prevalence of the ATEHL was significantly higher in specimens with a HV deformity (26/32, 81.25 %) compared to specimens without a HV deformity (6/32, 18.75 %) (p < 0.001). A positive correlation was found between ATEHL existence and both HVA and IMA degrees (p < 0.001).

Conclusions: An ATEHL may be found in more than half of individuals. The current cadaveric and radiologic study revealed that ATEHL existence is significantly more common in feet with HV deformity and associated with increased HVA and IMA degrees. Further biomechanical studies are necessary to clarify the ATEHL role on the pathogenesis of HV deformity.