The pars defect as a pain source. A histologic study.

Study Design. Tissue from the pars defects of six adult patients with symptomatic spondylolysis and spondylolisthesis was obtained at surgery. A histologic study was conducted to identify and characterize neural elements in this tissue. Objectives. To determine if nociceptive nerve endings were present within the pars defect of patients with symptomatic spondylolysis. Summary of Background Data. The origin of back pain in patients with spondylolysis remains uncertain. The defect in the pars interarticularis has been implated as a possible pain source. Methods. The solft tissue form the pars defect was obtained at surgery. A modified gold chloride stain was used to prepare the tissue for histologic examination. Tissue blocks were sectioned and studied under light microscopy. Results. Neural elements were found in all specimens examined. Free nerve endings believed to have nociceptive function were identified in all specimens. The density of neural elements varied betwseen specimens. Conclusions. The finding of neural elements, including free nerve endings within the pars defect tissue, suggests that the pars defect may be a source of back pain in some paitents with symptomatic spondylolysis.