Review Question - QID 3531

During the posterior approach to the hip, the most predictable course of the sciatic nerve is deep to the piriformis and superficial to the short external rotators exiting above the superior gemellus. As such, most recommend identification of the sciatic nerve by palpation in primary THA. In revision THA, many advocate identification of the sciatic nerve by both palpation and direct visualization.

The most common anatomic variant in the relationship of the short external rotators and the sciatic nerve is with the sciatic nerve traveling between the capsule and the short external rotators exiting below the superior gemellus.

Smoll reviewed the anatomy of the gluteal region and sciatic nerve anomalies in a meta-analysis and review of over 6000 cadavers. They concluded that the anomalies were present in about 16.8% of cadavers. They recommended a heightened awareness of the anomalies in hip surgery. The most common variants are found in Illustration D which were also supported by an earlier Beaton et al study.

Illustrations A,B and C depict the anatomy of the gluteal region including the anatomic relationship of the sciatic nerve to the short external rotators.