Nerve Endings in the Human Lumbar Spinal Column and Related Structures

Abstract

The nerve terminals of the human lumbar vertebral column and its related structures were studied with cholinesterase and silver-impregnation techniques in specimens from twenty-one autopsies (including two fetuses and two newborn infants) and fifteen surgical procedures. Nerve endings of three morphological types were found: (1) free fiber endings, (2) complex unencapsulated endings which sometimes had expanded tips, and (3) encapsulated endings. In the fetuses and newborn infants, encapsulated (Vater-Pacini) endings were primarily concentrated around the facet-joint capsules and on the ventrolateral surface of the annulus fibrosus. Many free nerve fibers and nerve networks were found in the anterior and posterior longitudinal ligaments and in the peripheral layers of the annulus fibrosus. No nerve elements were found in the deeper zones of the annulus or in the nucleus pulposus. The cartilaginous end plates of the vertebrae had a nerve supply closely associated with the vascular sinusoids in the developing tissues of the fetuses and infants. In the adult specimens, fine free nerve fibers were observed in practically all anatomical locations studied. Complex, unencapsulated endings were concentrated primarily in the periosteum of the lumbar vertebrae and within the synovial intervertebral facet-joint capsules. Encapsulated nerve terminations were found only in the region of the fibrous facet capsules in the adult tissues. No significant increase in nerve elements was observed in several degenerated lumbar dises studied with the cholinesterase technique. Nerve fibers usually considered to be pain sensitive were found in the loose areolar tissue and periphery of the annulus fibrosus but none was seen within the body of the disc or in the nucleus pulposus.