Acute histologic effects and thermal distribution profile of disc biacuplasty using a novel water-cooled bipolar electrode system in an in vivo porcine model.

BACKGROUND: Thermal treatment of the lumbar intervertebral disc has been suggested for the treatment of chronic discogenic pain. Disc biacuplasty (D-BAC) is a novel procedure that uses two water-cooled radiofrequency electrodes in a bipolar configuration to heat a large volume of the posterior annulus fibrosus. METHODS: Seven porcine lumbar discs were treated with D-BAC to assess acute effects on the treated tissue in a "worst-case"in vivo model. Intradiscal and peridiscal temperatures were measured during treatment and histologic analysis was used to assess for evidence of acute thermal injury. RESULTS: Temperature monitoring at designated safety zones outside the disc demonstrated maintenance of near-physiologic conditions while temperature in the inner posterior annulus reached 65 degrees C. Histologic sections of treated discs demonstrated no evidence of thermal damage to the dorsal root ganglia or spinal nerve roots when compared with controls. Increased coarseness of the fibrillar matrix and loss of cellular detail were noted in the nucleus pulposus of treated discs. DISCUSSION: Disc biacuplasty, in a porcine model, achieves suitable temperatures to induce thermal transition of collagen and thermoneurolysis while showing no evidence of damage to neural tissue in safety zones surrounding the disc.