While performing a caudal epidural block in a child, the anaesthetist identifies the sacral hiatus bounded laterally by the sacral cornua. Through which structure does the needle enter the sacral canal?

• A Sacrococcygeal membrane ✓
• B Posterior sacroiliac ligament
• C Sacrotuberous ligament
• D Thoracolumbar fascia

Explanation

The sacral hiatus is the midline defect formed by failure of fusion of the fifth (usually fourth and fifth) sacral laminae, and it is closed inferiorly by the sacrococcygeal membrane, a remnant of the supraspinous and interspinous ligaments. The needle passes through this membrane into the sacral canal. The sacrotuberous and posterior sacroiliac ligaments are unrelated pelvic stabilisers, and the thoracolumbar fascia lies at the lumbar region entirely above the target.

Reference: Gray's Anatomy for Students, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.