When performing a lumbar puncture, the needle is inserted in the midline at the level of the intercristal line (Tuffier's line). This line most reliably corresponds to which vertebral level?
- A L3–L4 interspace (or L4 body) ✓
- B L1–L2 interspace
- C L5–S1 interspace
- D T12–L1 interspace
Correct answer: A. L3–L4 interspace (or L4 body)
Explanation
Tuffier's (intercristal) line connects the highest points of both iliac crests and crosses the vertebral column at the L3–L4 interspace or the spinous process/body of L4 in most adults. This is the standard surface landmark for lumbar puncture (LP), which is safely performed below the conus medullaris (which ends at L1–L2 in adults, L3 in neonates). LP is typically done at L3–L4 or L4–L5. Accessing L1–L2 risks conus injury. L5–S1 is occasionally used but is less accessible. T12–L1 is above the safe zone.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.