Trigger point of the posterior iliac crest: painful iliolumbar ligament insertion or cutaneous dorsal ramus pain? An anatomic study.

A trigger point is frequently found over the iliac crest at 7 to 8 cm from the midline in low-back-pain syndromes. Previously, this was described as either a painful insertion site of the iliolumbar ligament or pain in the distribution of the cutaneous dorsal ramus of the first or second lumbar nerve. The authors performed 37 dissections, and they report their anatomic findings. The iliac insertion of the iliolumbar ligament is inaccessible to palpation, being shielded by the iliac crest. The dorsal rami of L1 or L2 nerve roots, however, cross the crest at 7 cm from the midline, and this distance closely correlates with the dorsal projection of the iliolumbar ligament insertion. These rami are superficial and dorsal to the crest, easily accessible to palpation. In two of the 37 dissections performed, some rami were found to be narrowed as they crossed through an osteofibrous orifice over the crest, thus being susceptible to an entrapment neuropathy. The authors conclude that the trigger point sometimes localized over the iliac crest at 7 cm from the midline likely corresponds to elicited pain from a cutaneous dorsal ramus originating from the thoracolumbar junction rather than from the iliac insertion of the iliolumbar ligament.