McGaugh JM, Brismée JM, Dedrick GS, Jones EA, Sizer PS
Palpation reference line coursing between the superior-most aspect of the iliac crests has been reported to cross the L4 spinous process or L4/L5 intervertebral space in approximately 80% of the population. Comparable data have not been defined for the line coursing between the posterior superior iliac spines (PSIS). The purpose of this study was to compare the anatomical consistency of the PSIS to the iliac crest as landmarks used for spinal palpation. One hundred computerized tomographic images were reviewed in a three-dimensional setting. The PSIS corresponded to the S2 spinous process in 81% of subjects and the iliac crest to the L4 spinous process in 59% of subjects. Distance measures suggest that the PSIS was closer to S2 versus the iliac crest to L4 and the PSIS crossed S2 more frequently than the iliac crest crossed L4. The study findings support the relationship between the PSIS, and the spinous process of S2 is more consistent when compared to the iliac crest and the spinous process of L4. The authors conclude that the PSIS reference line may be used to find S2 as a reference standard in validity and reliability palpation studies in the lower lumbar spine.
Clinical Anatomy, 2007, online article ahead of print