title: Sex differences in the branching position of the nerve to the abductor digiti minimi muscle: an anatomical study of cadavers.
abstract: 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.
authors.affiliation: Department of Anatomy, Aichi Medical University School of Medicine, Nagakute, Aichi 480-1195 Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Mizuno
authors.affiliation: Department of Anatomy, Aichi Medical University School of Medicine, Nagakute, Aichi 480-1195 Japan.
authors.forename: Munekazu
authors.initials: M
authors.lastname: Naito
authors.affiliation: Department of Anatomy, Tokyo Medical University School of Medicine, Shinjuku-ku, Tokyo Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Hayashi
authors.affiliation: Department of Anatomy, Aichi Medical University School of Medicine, Nagakute, Aichi 480-1195 Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Ohmichi
authors.affiliation: Department of Anatomy, Aichi Medical University School of Medicine, Nagakute, Aichi 480-1195 Japan.
authors.forename: Mika
authors.initials: M
authors.lastname: Ohmichi
authors.affiliation: Department of Anatomy, Aichi Medical University School of Medicine, Nagakute, Aichi 480-1195 Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakano
keywords: Abductor digiti minimi muscle; Cadaver dissection; Heel pain; Lateral plantar nerve; Posterior tibial nerve; Sex difference