Movements of the lumbo-sacral nerve roots in the spinal canal induced by straight leg raising test: an anatomical study.

PURPOSE: The pain involved in the herniated discs could be generated by some mobility of the nerve roots during straight leg raising (SLR). SLR produces some movement of nerves, but the magnitude of this displacement needs to be thorough, that is why we have investigated lumbo-sacral nerve root displacement in the spinal canal during the passive straight leg raise (SLR).

METHODS

Fourteen cadavers underwent laminectomy to mark the nerve roots of L2-S1 with lead balls. X-rays were taken during different movements imposed on the body: bilateral hip extension, left SLR then right and bilateral SLR. By superimposing these images two by two, the displacement of the nerve roots is quantified numerically during the various SLR maneuvers with respect to the reference position corresponding to the bilateral hip extension.

RESULTS

The median range of the different nerve root movements ranged from 0.10 to 0.51 cm (p < 0.05 except for the L2 root) when the left SLR is applied, from 0.26 to 0.48 cm (p < 0.05) with the right SLR and from 0.30 to 0.65 cm (p < 0.05) with a bilateral SLR. No statistically significant relationship was found between age and movement value.

CONCLUSIONS

The lumbo-sacral nerve roots in the spinal canal region move statistically significantly in response to the clinically applied SLR test, except for L2 root during the left SLR. This movement is symmetric and greater when a bilateral SLR is applied. These anatomical results are correlated with those observed empirically in clinical practice.