The skin dimples overlying the posterior superior iliac spines are used as a surface landmark during spinal procedures. These dimples indicate which vertebral level, a fact that matters because the dural sac terminates at this level in adults?
- A L4
- B S2 ✓
- C S1
- D L5
Correct answer: B. S2
Explanation
A line joining the two posterior superior iliac spines crosses the S2 vertebra, identifiable on the surface as the dimples of Venus. In adults the dural sac and subarachnoid space end at the S2 level, so a needle passed through the posterior sacral foramina or the sacral hiatus stays extradural if kept below this line. L4 is the intercristal level used for lumbar puncture, and S1 lies above the termination of the dural sac.
Reference: Moore's Clinically Oriented Anatomy, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.