Sex differences in the branching position of the nerve to the abductor digiti minimi muscle: an anatomical study of cadavers

BACKGROUND: The nerve to the abductor digiti minimi muscle (ADMM nerve) is the first branch of the lateral plantar nerve or originates directly from the posterior tibial nerve. Damage to the ADMM nerve is a cause of heel pain and eventually results in ADMM atrophy. It is known that ADMM atrophy occurs more often in females than in males, and the reason remains unclear. This study aimed to explore sex differences in the branching pattern, position, and angle of the ADMM nerve. METHODS: Forty-two cadavers (20 males, 22 females) were dissected at Aichi Medical University between 2011 and 2015. Cases of foot deformity or atrophy were excluded and 67 ft (30 male, 37 female) were examined to assess the branching pattern, position, and angle of the ADMM nerve. RESULTS: The branching positions of the ADMM nerve were superior to the malleolar–calcaneal axis (MCA) in 37 ft (55 %), on the MCA in 10 ft (15 %), and inferior to the MCA in 20 ft (30 %). There was no case among male feet in which the ADMM nerve branched inferior to the MCA, whereas this pattern was observed in 19 of 37 female feet (51 %). The branching position of the ADMM nerve was significantly closer to the MCA in female feet than in male feet. There were no significant sex differences in the branching pattern and angle of the ADMM nerve. CONCLUSIONS: The ADMM nerve sometimes branches off inferior to the MCA in females, but not in males. This difference may be the reason for the more frequent occurrence of ADMM atrophy in females than in males.