Extensor hallucis longus innervation: an anatomic study.

Thirty legs from skeletally mature embalmed cadavers were dissected to define the most common pattern and the variants of innervation of the extensor hallucis longus muscle and its clinical significance. Twenty-seven muscles had only one innervating branch (90%). Only three muscles had two innervating branches (10%). Twenty-one of the branches entered the muscles from the fibular side (63.6%), six entered the muscles from the tibial side (18.2%), and six entered the muscles from the anterior edge (18.2%). The branches innervating the extensor hallucis longus from the fibular side had a closer relation with the fibular periosteum than those entering the muscle from the tibial side or the anterior edge. The mean length of these branches between their points of origin and entry in the extensor hallucis longus was 5.0 +/- 1.5 cm. The high risk zone for the iatrogenic injury to the muscular branch of the extensor hallucis longus was located between 5.9 +/- 1.7 and 10.9 +/- 1.7 cm inferior to the most distal palpable point of the fibular head. The current study confirmed that the extensor hallucis longus was supplied mostly by one nerve that usually entered the muscle from the fibular side and had a close relation to the fibular periosteum in the dangerous zone.