Sclerotomes in the Thoracic and Lumbar Spine, Pelvis, and Hindlimb Bones of Rats

Abstract Pain in lumbar radiculopathy shows a segmental distribution in muscles and bones, requiring knowledge of myotomes and sclerotomes for diagnosis of the involved nerve roots. The rostrocaudal coordinate in sensory space was examined for 49 reference sites placed on the periostium in the spine and hindlimb bones of rats to clarify the sclerotomes. Neurotracer 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI) was applied to reference sites. DiI-labeled neurons were counted from the T9 through S3 dorsal root ganglia. The coordinate was calculated for each reference site as the location of the “median” neuron of all DiI-labeled neurons. The coordinate was between T13 and L3 for the lumbar spine, L2 and S1 in the coxal bone, L3 and L4 in the hip joint, femur, knee joint, tibia, and first digit, and L5 in the fibula and fifth digit. The routes of sclerotome boundary lines (SBLs) were determined based on the coordinates of the reference sites. SBLs obliquely demarcated the lumbar spine. SBLs were aligned parallel rostrodorsally to caudoventrally in the coxal bone, with medially-oriented convergence. The SBL between L3 and L4, which corresponded to the level of the furcal nerve, passed from the femur, tibia, and toward the first digit in the hindlimb bones. Perspective The present study is the first report of the detailed sclerotome chart of rats. The sclerotome chart is not only useful for basic research of lumbar radiculopathy using rats, but would also facilitate an understanding of the spatial distribution of pain in patients with lumbar radiculopathy.