Multiple muscular variations including tenuissimus and tensor fasciae suralis muscles in the posterior thigh of a human case

The posterior thigh muscles on the right side of an 81-year-old male cadaver had multiple variations, denoted muscles I–IV. Muscle I originated from the posteromedial surface of the greater trochanter and divided into two muscle bellies. These muscle bellies fused with the long head of the biceps femoris and were innervated by two branches from muscular branches of the semitendinosus and the long head of the biceps. Muscle II separated from the medial surface of the long head of the biceps in the proximal third and fused with the semitendinosus in the distal fourth. Muscle III was a biventer muscle. Its superior belly separated from the medial surface of the long head of the biceps in the distal third. The inferior belly of this muscle fused with the posterior surface of the crural fascia and was innervated by the tibial nerve. Muscle IV separated from the adductor magnus muscle, passed between the long and short heads of the biceps, fused with the inferior belly of muscle III, and was innervated by the muscular branch of the common fibular nerve to the short head of the biceps. Peeling off the epineurium of the muscular branches to the inferior belly of muscle III showed that this nerve fascicle divided from the common trunk with branches to the gastrocnemius and soleus muscles. The inferior bellies of muscle III and muscle IV were thought to be equivalent to the tensor fasciae suralis and tenuissimus muscles, respectively.