[Innervation of the sacroiliac joint of the human]

The innervation of the human sacroiliacal joint was investigated on adult cadaveric specimens devoted for routine dissection courses, and on fetuses obtained from therapeutic abortions. Gross anatomical and microscopic dissection, histology of dissected nerves, and histological and immunocytochemical approaches were used. Innervation of the iliosacral joint is provided by fine nerve branches derived exclusively from dorsal rami of spinal nerves S1-S4. No branches could be detected from the plexus sacralis and obturator nerve coursing over the ventral aspect of the joint. Nerves were distributed to superficial and deep dorsal sacroiliac ligaments, and to the sacrotuberous and sacrospinous ligaments. Dorsal spinal rami continued their course laterally, sandwiched between superficial and deep portions of sacroiliac ligaments, piercing the origin of the glutaeus maximus muscle. Histological examination of dissected nerves demonstrated numerous thick myelinated, besides thin myelinated and unmyelinated nerve fibers compatible with a broad repertoire of sensory receptors including encapsulated mechanoreceptors. Histological and immunocytochemical studies on fetal iliosacral joints showed neurofilament positive nerve fibers only in dorsal portions. This innervation pattern may provide explanations for various patterns of pseudoradicular and referred pain in affections of the sacroiliac joint.