Accessory muscle belly of peroneus tertius in the leg--a rare anatomical variation with clinical relevance--utility in reconstructions.

We report here a rare muscular anomaly of the lower leg in an adult male cadaver observed during routine cadaveric dissection. Peroneus tertius (PT) is peculiar to man, being a hallmark of bipedal locomotion and erect posture. During the course of gross anatomy dissection, a rare finding of accessory belly of PT muscle was discovered. A meticulous dissection was performed and the observations were noted. The PT displayed two distinct bellies of origin. Both the bellies were substantial in size and were eventually fused close to their insertion at the base of the fifth meta-tarsal bone. Innervation of both the bellies was derived from the deep peroneal nerve. Soft tissue defects of the leg may be effectively covered by local muscles in the vicinity of the wounds. PT has been reliably used in the past for local transposition flaps in the lower extremities. The relations of the superficial nerve and the PT during placement of the anterolateral portal in ankle arthroscopy are vital to avoid inadvertent neuromuscular injuries. The presence of two bellies of the PT muscle has been discussed in the comparative perspective. A precise and detailed knowledge of the anatomical details of the crural muscles is important for performing reconstructive surgeries.