Extraspinal course of the fifth lumbar spinal nerve: An update of its topographical relationships

Abstract

The fifth lumbar spinal nerve traverses a highly mobile transitional junction of the vertebral column. Evidence suggests that it is often implicated in the etiology of low-back pain, notably in entrapment syndromes. There appears to be a high incidence of unsuccessful attempts at surgical decompression in cases of suspected entrapment of the nerve, suggesting that perhaps the anatomical information on the topography of the nerve is incomplete. The present study examined the course and relations of the fifth lumbar spinal nerve by gross dissection of human cadaveric material. The results showed that the nerve and its subdivisions follow a complex, tortuous course as they cross the lumbosacral junction. The trunk and ventral and dorsal rami are all related to strong ligaments that are thought to be protective. The nearness of these nerves to ligaments in such an area of high mobility, however, predisposes them to impingement or entrapment in the event of joint or ligamentous pathology. It is suggested therefore that investigations of spondylogenic low-back pain should include a detailed evaluation of the status of all parts of the fifth lumbar spinal nerve as they traverse their individual osteoligamentous compartments.