Case of High Origin of the Common Peroneal Nerve Accompanied by Variation in the Sacral Plexus and the Piriformis Muscle

摘要

During routine tutorial in gross anatomy, we encountered a case (female, older than 60 years) of altered gross anatomy of the sacral plexus and the piriformis muscle, and altered passage and distribution of the superior and inferior gluteal arteries and their branches. From the lumbosacral trunk and the ventral division of S2 arise branches, which form a second plate. This plate is situated behind the sacral plexus and passes through the piriformis muscle dividing it into two separate parts. It separates the superior gluteal nerve and the common peroneal nerve. The latter leave the pelvis between the two parts of the piriformis muscle. The anterior plate of the sacral plexus divides into the inferior gluteal nerve, the pudendal nerve and the tibial nerve. The posterior cutaneous femoral nerve begins with two roots arising from the two plates of the sacral plexus. The superior gluteal artery has large diameter and its descending branch takes over the blood supply of the gluteus maximus muscle. The inferior gluteal artery and the obturator artery arise from a common trunk originating from the posterior branch of the internal iliac artery. The inferior gluteal artery leaves the pelvis through the infrapiriform opening. It passes behind the tendon of the internal obturator muscle and splits into several branches providing blood supply for the latter muscle, the gemmeli muscles and partially for the head of the femur and the capsule of the hip joint.