Poster 84: Tumor Necrosis Factor-Alpha Levels in Herniated Intervertebral Disks

Abstract

Objective: To determine if tumor necrosis factor-alpha (TNF-α) is present in elevated concentrations within the central aspect of the disk in patients with symptomatic disk herniations. Design: Controlled immunochemical study. Setting: University academic center. Participants: Consecutive subjects undergoing percutaneous disk decompression (PDD) for radicular pain (n=20) and undergoing fusion for axial pain (n=20), serving as controls. Intervention: Nuclear material was removed from the central part of the disk using a fluoroscopically guided percutaneous decompression probe. Tissue was homogenized in a protease inhibitor buffer and assayed for the presence of TNF-α using a colorimetric enzyme linked immunosorbent assay. Control samples were taken from disks of surgical patients undergoing fusion and analyzed in the same manner. Main Outcome Measure: TNF-α concentration. Results: TNF-α was detected in the disk nucleus of patients who presented with a herniated disk and radicular pain in a statistically greater concentration than in disks from patients presenting with axial pain. Mean concentration of TNF-α was 411.2pg/mg tissue in the PDD group, which was significantly higher (Wilcoxon rank-sum test, P<.05) than TNF-α levels detected in the fusion group. Conclusions: TNF-α is a potent inflammatory cytokine that has been implicated in the pathophysiology of disk degeneration as well as radicular pain resulting from herniated disks. Prior studies have demonstrated the presence of TNF-α at the interface between the herniated disk tissue and the nerve root. In addition, the ability of nucleus pulposus cells to synthesize TNF-αin culture has been demonstrated. We report the novel observation that TNF-α is present in significantly higher concentrations in vivo in the nucleus pulposus of patients with herniated discs than in nonherniated control discs and at a site remote from the disk-nerve root interface.