Background The intercristal line (ICL), defined by the superior aspect of the iliac crest, is used to clinically identify the entry point for lumbar puncture (LP) in neonates. Accepted practice is to insert the needle at the L3/4 or L4/5 intervertebral space.

Aim To investigate the vertebral level crossed by the ICL as determined by manual palpation and the ability of manual palpation to reliably identify a specified intervertebral space.

Method A total of 30 term neonates were recruited. Paediatricians identified and marked the ICL and the intervertebral space above, with babies in left lateral position. The anatomical positions of both points and the end of the conus medullaris were confirmed using ultrasonography.

Results The ICL was marked from L2/3 to L5/S1. In 25 babies (83%), the ICL was identified at the desired vertebral level between L3/4 and L4/5. The intervertebral space above this line was marked between L1/2 to L4/5. The potential site for LP was identified higher than intended in 11 cases (36%). The end of the conus medullaris ranged from L1 to L3 terminating at L2 or lower in 11 cases (36%).

Conclusions There are wide variations in the positions of the ICL and potential LP site. Using the ICL to guide LP does not appear to be accurate, raising the possibility of potential spinal cord damage.