2006 Young Investigator Award Winner: lumbosacral nerve root displacement and strain: part 1. A novel measurement technique during straight leg raise in unembalmed cadavers.

STUDY
DESIGN: A descriptive cadaveric study incorporating a novel nerve root marking technique.
OBJECTIVES: To describe the displacement and strain of the lumbosacral nerve roots in the lateral recess during straight leg raise (SLR) without disrupting the foraminal ligaments. SUMMARY OF BACKGROUND DATA: Previous studies document 2 to 8 mm of lumbosacral nerve root displacement during SLR. Prior dissection methods incorporated laminectomy and facetectomy.
METHODS: Lower limbs and associated nerve roots of 5 unembalmed cadavers (n = 10) were studied. Metal markers were inserted intraneurally within the lateral recess of L4, L5, and S1 with a modified spinal needle. Fluoroscopic images were digitized to evaluate displacement and strain during SLR.
RESULTS: The lumbosacral nerve roots in the lateral recess moved less and experienced less strain during SLR than described in previously published reports. Statistically significant distal displacement occurred at hip positions greater than 60 degrees of flexion at all nerve root levels (P < 0.01).
CONCLUSIONS: The lumbosacral nerve roots (L4, L5, S1) moved less and underwent less strain during SLR testing than previously reported and may require hip motion greater than 60 degrees to produce substantive displacement in the lateral recess. Additional research is needed to examine the effects of prepositioning during SLR.