Unilateral absence of an extensor digitorum longus muscle and variations of toe tendons

Introduction During routine dissection in the gross anatomy course, the author was called to confirm the absence of the right extensor digitorum longus (EDL) muscle in a 49-year-old Caucasian male who died of pneumonia. Once confirmed, the author also noted the left foot had only a single EDL tendon to the fifth toe. Further dissection by the author revealed other tendon variations. During the dissection of almost 1,400 cadavers, this was the first time these variations were seen. The EDL muscle is found in the anterior compartment of the leg and is the primary extensor of the second-fifth toes; it is innervated by the deep fibular nerve. The function of the EDL is assisted by the extensor digitorum brevis (EDB) muscle that sends tendons to the second-fourth toes. Much like the tibialis anterior and fibularis tertius muscles, the EDL functions to dorsiflex the foot and toes for ground clearance during the swing phase of walking [1]. The fibularis tertius tendon can be absent in up to 10% of the population, and it often appears to be part of the EDL where it has been described as its “fifth tendon” [2]. During surgical procedures, EDL tendons can be used for tendon grafts [3]. Although its presence has not been questioned by surgeons, its potential absence could present a surgical hindrance if EDL tendons are used for ankle stabilization.