ANATOMIC BASES OF MEDICAL, RADIOLOGICAL AND SURGICAL TECHNIQUES M. del Sol ® E. Olave ® Carla Gabrielli Eduardo Mandiola ® J. C. Prates Innervation of the abductor digiti minimi muscle of the human foot: anatomical basis of the entrapment of the abductor digiti minimi nerve Received: 19 October 2001 / Accepted: 5 January 2002 / Published online: 29 March 2002 Ó Springer-Verlag 2002 Abstract The origin, relationships and innervation of the abductor digiti minimi muscle were determined in 145 human feet, from formaldehyde-fixed cadavers. The muscle arises from both processes of the calcaneal tub- erosity, from the plantar aponeurosis and from the septum which separates it from the flexor digitorum brevis muscle. The nerve to the abductor digiti minimi muscle arises next to the origin of the lateral plantar nerve, close to the abductor hallucis muscle, and de- scends becoming closely related to the medial face of the calcaneus and the deep face of the abductor hallucis muscle. Then, it passes inferiorly through the origin of the quadratus plantae muscle and later divides into two branches for the two heads of the muscle. Innervation du muscle abducteur du petit orteil. Base anatomique de la compression de son nerf Re´ sume´ L’origine, les rapports et l’innervation du muscle abducteur du petit orteil ont e´te´ e´tudie´s sur 145 pieds humains issus de cadavres formole´s. Le muscle naıˆt des deux processus de la tube´rosite´ calcane´enne, de l’apone´vrose plantaire et du septum qui le se´pare du muscle court fle´chisseur des orteils. Le nerf du muscle abducteur du petit orteil naıˆt pre`s de l’origine du nerf plantaire late´ral, juste a` coˆte´ du muscle abducteur de l’hallux et descend en rapport e´troit avec la face me´diale du calcane´us et la face profonde du muscle abducteur de l’hallux. Il se dirige ensuite vers le bas a` travers l’origine du muscle carre´ plantaire et se divise ensuite en deux branches destine´es a` chacun des chefs du muscle. Keywords Foot ® Muscles ® Tibial nerve ® Nerve compression syndromes Introduction Traditionally, the plantar region has been divided into three parts: medial, intermediate and lateral. Therefore in most textbooks the abductor digiti minimi is located in the lateral compartment of the plantar region. The muscle arises from the two processes of the calcaneal tuberosity, from the intervening bone, from the plantar aponeurosis and from the intermus- cular septum separating it from flexor digitorum brevis [11, 14, 17]. Subcalcaneal pain of non-traumatic origin can be caused by compression of the nerve of the abductor digiti minimi by the calcaneal spur [1, 2, 5]. This branch takes a lateral course through the sole, lies in the prox- imal portion of the long plantar ligament and divides into two branches, namely anterior and posterior, which enter the abductor digiti minimi immediately adjacent to the calcaneal tuberosity [3, 5]. It has been stated that this nerve arises from the lateral plantar nerve or directly from the tibial nerve in a common trunk with the plantar nerves and the medial calcaneal branches [1, 8]. In some cases, it arises from a common trunk with the posterior branch for the quad- ratus plantae [4]. The muscle receives sometimes two branches from the lateral plantar nerve: from a posterior branch which penetrates into the proximal part of the muscle, next to its origin in the calcaneus, and from another which penetrates into the muscle at the level of the fifth metatarsal [12]. This last branch is a branch for the flexor digiti minimi brevis [6]. Surg Radiol Anat (2002) 24: 18–22 DOI 10.1007/s00276-002-0001-1 M. del Sol (&) ® E. Olave Faculty of Medicine, Universidad de La Frontera, Casilla 54-D, Temuco, Chile E-mail: mdelsol@ufro.cl Tel.: +56-45-284343 C. Gabrielli Department of Morphological Sciences, Universidade Federal de Santa Catarina, Brazil E. Mandiola Faculty of Medicine, Universidad Andre´s Bello, Santiago, Chile J.C. Prates Escola Paulista de Medicina, Universidade Federal de Sa˜o Paulo, Brazil