M. flexor digitorum longus accessorius in the lower limb of man.

An atypical m. flexor digitorum longus accessorius was observed on the shin of the left pelvic limb. The muscle originates with 2 heads from the middle third of the tibia and from the deep leaf of the shin fascia. Its tendon descends to the planta pedis (passing through a separate tendon sheath in the region of the medial ankle). In the planta pedis it joins the tendons of the long flexor for the 2nd to 4th toes and takes in the strong tendon link of the m. flexor hallucis longus. A similar case was observed on the shin of the right pelvic limb. The muscle originates from the dorsal surface of the tibia, its tendon running below the retinaculum flexorum in a separate tendon sheath, and in the planta pedis it merges with the tendon of the m. flexor digitorum longus. Besides the accessory long flexors of the toes, there was described a muscle link between the heads of the m. flexor digitorum longus and m. flexor hallucis longus. The presence of the accessory toe flexor is, together with the existence of muscle links between the flexors in the region of the shin, evidence of regressive varieties.