INNERVATION OF THE HUMAN SACROILIACAL JOI NT

The innervation of the human sacroiliacal joint was investigated on ad ult cadaveric specimens devoted for routine dissection courses, and on fetuses obtained from therapeutic abortions. Gross anatomical and mic roscopic dissection, histology of dissected nerves, and histological a nd immunocytochemical approaches were used. Innervation of the iliosac ral joint is provided by fine nerve branches derived exclusively from dorsal rami of spinal nerves S1 - S4. No branches could be detected fr om the plexus sacralis and obturator nerve coursing over the ventral a spect of the joint. Nerves were distributed to superficial and deep do rsal sacroiliac ligaments, and to the sacrotuberous and sacrospinous l igaments. Dorsal spinal rami continued their course laterally, sandwic hed between superficial and deep portions of sacroiliac ligaments, pie rcing the origin of the glutaeus maximus muscle. Histological examinat ion of dissected nerves demonstrated numerous thick myelinated, beside s thin myelinated and unmyelinated nerve fibers compatible with a broa d repertoire of sensory receptors including encapsulated mechanorecept ors. Histological and immunocytochemical studies on fetal iliosacral j oints showed neurofilament positive nerve fibers only in dorsal portio ns. This innervation pattern may provide explanations for various patt erns of pseudoradicular and referred pain in affections of the sacroil iac joint.