The depth of the lumbar epidural space from the skin.

The depth of the epidural space at different intervertebral interspaces was measured in 1000 parturients. Overall the median distance from the skin to the epidural space was 4.7 cm, but this varied with the lumbar interspace at which it was measured, being greatest at the third (L3-4) interspace (4.93 cm) and least at the first (L1-2) interspace (4.23 cm). The clinical significance of these findings is discussed.