Innervation of the Rabbit Lumbar Intervertebral Disc and Posterior Longitudinal Ligament

Abstract

The present study sought to determine to what extent the lumbar intervertebral disc and posterior longitudinal ligament are innervated in the New Zealand white rabbit. The intent is to use this disc model in future neurophysiology studies. To characterize the distribution of nerve fibers and endings in the lumbar intervertebral disc and posterior longitudinal ligament in an animal model. The results of previous disc innervation reports are somewhat conflicting regarding the density and depth of innervation into the anulus. A silver impregnation technique was used to analyze sections from lumbar intervertebral disc and posterior longitudinal ligament of the New Zealand white rabbit. Numerous fine profiles of nerve fibers were demonstrated in the lumbar disc anulus and posterior longitudinal ligament. In the disc, the nerves were limited to the superficial anulus and anular surface. The nerve axons typically were 1 to 3 μm in diameter and were found around the entire periphery of the disc. No encapsulated endings were seen within the anulus, while occasional encapsulated endings were seen on the anular surface and posterior longitudinal ligament. This study demonstrates an extensive distribution of small nerve fibers in the size range of C and A-delta fibers throughout the peripheral anulus and provides an illustration of this distribution. These findings support a role for the disc as a source of low back pain.