During a posterior approach to total hip replacement, the piriformis muscle is a key surgical landmark. Which important neurovascular structure lies inferior to piriformis in the greater sciatic foramen and is most at risk in posterior hip dislocations?

• A Sciatic nerve ✓
• B Superior gluteal nerve and artery
• C Obturator nerve
• D Pudendal nerve

Explanation

The piriformis muscle divides the greater sciatic foramen into superior and inferior compartments. Structures above piriformis: superior gluteal nerve (L4-S1) and vessels. Structures below piriformis: sciatic nerve (most lateral), inferior gluteal nerve, nerve to obturator internus, nerve to quadratus femoris, posterior femoral cutaneous nerve, internal pudendal vessels, and pudendal nerve. The sciatic nerve is the largest structure exiting below piriformis and is most commonly injured in posterior hip dislocation and posterior approach surgeries.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.