Optimizing Peripheral Nerve Block Placement in Hip Surgery: A Cadaveric Study Mapping the Posterior Cutaneous Innervation.

Abstract

Optimizing analgesia after hip surgery enables more rapid recovery. However, peripheral nerve blocks (PNBs) often fail to provide adequate pain relief in the posterolateral hip as they typically target the lateral cutaneous nerve of the thigh (LCNT). This study aimed to map the nerves innervating the posterolateral hip through analysis of anatomy textbooks (n = 5) and cadaveric dissections (n = 13). The subcostal (SCN), iliohypogastric (IHN), and ilioinguinal (IIN) nerves were identified as key contributors to innervating the posterolateral hip. The optimal site for ultrasound-guided PNBs to target these three nerves was identified at the "75/25" landmark: 75% horizontally along the 12th rib and 25% vertically down to the iliac crest. Ultrasound-guided dye injections in cadavers (n = 6) showed that while the "75/25" landmark effectively stained the SCN (6/6) and IHN (4/6), it inconsistently stained the IIN (2/6). A second injection in the posterolateral hip stained branches of the IHN (4/6) and IIN (4/6) but not the SCN (1/6), suggesting the IHN and IIN are the dominant nerves in the posterolateral hip. These findings recommend a more distal injection at the "100/75" landmark to consistently block the IHN and IIN, thereby optimizing postoperative analgesia after hip surgery.