Movements induced by straight leg raising in the lumbo-sacral roots, nerves and plexus, and in the intrapelvic section of the sciatic nerve

Abstract

It is well known that on straight leg raising (Lasegue's test) traction is exerted on the sciatic nerve, the lumbo-sacral nerve roots, and the dura. The roots move through their intervertebral foramina for distances which may amount to several millimetres. If, however, dissection is made from the front instead of from the back (which is the usual approach) the course of the nerves and their changes with leg movements can be followed to the sciatic notch. This more extensive examination reveals several points not generally appreciated in descriptions of the sciatic nerve or in consideration ofthe significance of the straight-leg-raising test. In particular, it shows that nerve movements become progressively greater with increasing distance from the intervertebral foramina, and it establishes the existence of multiple points of pressure against the bone. Alterations in tension and the degree to which the roots are adherent to the intervertebral foramina are open to inspection. All of these changes can readily be examined and correlated with age. This paper incorporates the objective findings and the conclusions reached after a considerable number of dissections made by an anterior approach after routine necropsy, and it records measurements of the movements of those nerves commonly implicated in sciatic pain in a smaller series of 30 cases. TERMINOLOGYIn this paper the elements of the cauda equina are referred to as filia. From the point at which these evaginate the dural sheath around the cord to the point of fusion of the dorsal and ventral components distal to the ganglion, they are called roots. More distally again they are termed nerves, at first forming part of the lumbo-sacral plexus. The lumbosacral cord is that segment of the anterior primary division of the fifth lumbar nerve extending from the 'Present address: Pathology Department, Metropolitan General Hospital, Cleveland, Ohio, U.S.A. point at which it receives a contribution from the fourth lumbar nerve until its junction with the first sacral nerve, or that part of the fifth lumbar nerve which runs over the ala of the sacrum. MATERIAL AND METHODSCadavers were selected from routine necropsies as time and circumstance permitted. Although an attempt was made to obtain these as soon as possible after death and before refrigeration, a wide range of body temperatures was encountered, varying from warm fresh bodies to others which were very cold. Rigor mortis was present in varying degrees in most of these and had to be broken down by forcible ventroflexion of the hips and dorsiflexion of the knees. The ankles were not mobilized and were left at approximately 90 degrees to the leg.To retain anatomical stability and avoid loosening of the spinal dura, filia and nerve roots which, in the lumbosacral region, run with a ventral convexity in the spinal canal, and to afford exposure of the nerves running over the ala of the sacrum, a technique of anterior dissection with minimal interference to neural structures was devised. After removal of abdominal viscera, t...

Effects of Nucleus Pulposus on Nerve Root Neural Activity, Mechanosensitivity, Axonal Morphology, and Sodium Channel Expression

“…Mechanical stimulation includes compression from herniated disc and stretch of the nerve root as in the straight leg raising test. 41 Sodium channel has been found increased with 7-day and 21-day NP exposure in this study. Sodium channel blocking agents including carbamazepine 37,42 and lidocaine 36,43 may be useful to alleviate sciatic pain and paresthesia resulting from abnormal neural activity.…”

Validity of the Straight-Leg Raise Test for Patients With Sciatic Pain With or Without Lumbar Pain Using Magnetic Resonance Imaging Results as a Reference Standard

“…In the literature, several features have been investigated to identify the causes of a positive SLR test (nerve root compression, 18,21 damage to structures and collateral ligaments, 22 edema around nerve root, [23][24][25] nerve irritation, 26,27 venous obstruction, [28][29][30] shape, size or location of disk herniation, 31,32 blood perfusion, 33 and inflammatory cells or factors 34,35 ); however, no clear explanation has yet been found.…”

Strain and excursion of the sciatic, tibial, and plantar nerves during a modified straight leg raising test

“…The amount of longitudinal movement was in agreement with earlier findings. 6 Despite the widespread use of ankle dorsiflexion as a sensitizing maneuver, the supposition that this additional movement increases strain in the lumbosacral plexus remains unexamined.…”