INNERVATION OF THE LUMBAR FACET JOINTS - ORIGINS AND FUNCTIONS

Study Design. The levels of dorsal root ganglia and paravertebral symp athetic ganglia innervating the lumbar facet joint were investigated i n rats using the retrograde transport method. The pathways and functio ns of the nerve fibers supplying the lumbar facet joint were determine d immunohistochemically. Objectives. To study lumbar facet pain in rel ation to its innervation. Summary of Background Data The lumbar facet joints have been reported to be innervated segmentally. Little is know n, however, about the origins and functions of the nerve fibers. Metho ds. Cholera toxin B subunit, a neural tracer, was placed in the L5-L6 facet joint, and the bilateral dorsal root ganglia and paravertebral s ympathetic ganglia were examined immunohistochemically The serial sect ions of lumbar vertebrae of newborn rats and the sections of the facet joint capsules, dorsal root ganglia, and paravertebral sympathetic ga nglia of adult rats were investigated immunohistochemically. The pathw ays of the nerve fibers supplying the facet joint were reconstituted. Results. Labeled neurons existed in ipsilateral dorsal root ganglia fr om L1 to L5 and in paravertebral sympathetic ganglia from T12 to L6. T he dorsal ramus of the spinal nerve and rami communicantes were connec ted to each other by calcitonin gene-related peptide immunoreactive fi bers and dopamine p-hydroxylase immunoreactive fibers. Conclusions. Th e L5-L6 facet joint was innervated by ipsilateral dorsal root ganglia and paravertebral sympathetic ganglia, segmentally and nonsegmentally. Some of the sensory fibers from the facet joint may pass through the paravertebral sympathetic trunk, reaching L1 and/or L2 dorsal root gan glia. Inguinal and/or anterior thigh pain with lower lumbar facet join t lesions may be explained as referred pain.