A caudal epidural block is performed by injecting local anesthetic into the sacral epidural space through the sacral hiatus. Which structure forms the ROOF of the sacral hiatus that the needle penetrates?

• A Sacrococcygeal ligament ✓
• B Posterior longitudinal ligament
• C Ligamentum flavum of S1
• D Supraspinous ligament

Explanation

The sacral hiatus is the inferior opening of the sacral canal, formed by failure of fusion of the laminae of S5 and S4. It is covered posteriorly by the sacrococcygeal ligament (the caudal continuation of the ligamentum flavum and supraspinous ligament). The hiatus is bounded laterally by the sacral cornua. Caudal epidural anesthesia is performed by piercing the sacrococcygeal ligament to access the epidural space.

Reference: Gray's Anatomy, 42nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.