Anatomical study of human lumbar spine innervation

Abstract

To explore the detailed innervation of the lumbar spine of humans. Six adult cadavers fixed in a solution containing 10% formalin were investigated under a stereomicroscope. The lumbar spine, together with the abdominal aorta, inferior vena cava and psoas muscle, was extracted. The dissection was focused on various patterns of rami communicantes (RC), including superficial oblique rami (SOR) and deep transverse rami (DTR), and their relationship to the psoas major muscle, the minute nerve supply of the anterior and posterior longitudinal ligaments, vertebral bodies and the intervertebral discs. Two types of RC were observed: SOR and DTR. SOR ran obliquely between the superficial heads of the psoas major muscle, connecting the sympathetic trunk and T12-L2 spinal nerves non-segmentally. DTR, running along the lumbar arteries and veins, were distributed segmentally, close to the vertebral bodies. On the anterior aspect of the lumbar spine, the anterior longitudinal ligaments received branches from the sympathetic trunk and splanchnic nerves non-segmentally. On the lateral side of the lumbar spine, the vertebral bodies and the intervertebral discs received branches from the DTR and ventral rami segmentally, branches from the sympathetic trunk, and, in the upper lumbar region, SOR non-segmentally. Within the vertebral canal, the posterior aspect of the intervertebral discs and the posterior longitudinal ligaments received the sinu-vertebral nerves originating from DTR. Exist two different types of innervation in the lumbar vertebrae: one originating directly from the spinal nerve segmentally, and one reaching the vertebral body and intervertebral disc via the sympathetic nerves non-segmentally. Therefore, sympathetic nerves are involved in the innervation of the spinal column and intervertebral disc and are likely involved in discogenic low back pain.