Rare variation of flexor digitorum longus muscle of leg – a case report

The posterior compartment of leg is the largest but it diminishes markedly as it approaches the ankle. Flexor digitorum longus is thin and pointed proximally and gradually widens as it descends in the posterior compartment of leg. It arises from the posterior surface of the tibia medial to tibialis posterior from just below the soleal line to within seven or eight cm of the distal end of bone; it also arises from the fascia covering tibialis posterior. The muscle ends in a tendon that extends along almost the whole of its posterior surface. It passes deep to flexor retinaculum and enters sole of the foot. It continues across the sole to form the whole of long flexor tendons of the fifth toe and contributes to those of second, third and fourth toes. The tendons of quadratus plantae insert into the flexor digitorum longus tendons of the second, third and fourth toes. The long flexor tendons of the lateral four toes are attached to the plantar surfaces of the bases of their distal phalanges. It is innervated by branches of the tibial nerve [1]. Multiple accessory, supernumerary and variant muscles have been described in the anatomic, radiologic and surgical literature. Here, we present a case report of a variant muscle originating from the tendon of flexor digitorum longus muscle of the leg. Case Report Sixty inferior extremities of thirty embalmed adult human cadavers were studied in the Department of Anatomy, Govt. Medical College, Amritsar. They were dissected as per dissection steps provided by Cunningham’s Manual of Practical Anatomy [2]. The cadavers were labeled from one to thirty with suffix R (right) or L (left) extremity and M (male) or F (female). Out of sixty lower limbs, a variant muscle was observed in a male cadaver. It was a unilateral variation seen in left lower limb. A small muscle was originating from the tendon of flexor digitorum longus, going between flexor hallucis longus and tibialis posterior into the sole (Figure 1). Some of the fibers were originating from the fascia covering the flexor digitorum longus and tibialis posterior. The insertion of tendon of this variant muscle was traced, it merged with the tendon of flexor digitorum longus to the second toe and quadratus plantae (Figure 2). Nerve supply of this muscle was from a small branch of tibial nerve from its undersurface (Figure 1).