Acute biomechanical and histological effects of intradiscal electrothermaltherapy on human lumbar discs

Study Design. Human cadaver lumbar spines were used to assess the acute eff ects of intradiscal electrothermal therapy in vitro. Objective. To determine whether intradiscal electrothermal therapy produces acute changes in disc histology and motion segment stability. Summary of Background Data. Intradiscal electrothermal therapy has been int roduced as an alternative for the treatment of discogenic low back pain. Se veral hypothesized mechanisms for the effect of intradiscal electrothermal therapy have been suggested including shrinkage of the nucleus or sealing o f the anulus fibrosus by contraction of collagen fibers, and thermal ablati on of sensitive nerve fibers in the outer anulus. Methods. Intradiscal electrothermal therapy was performed with the Spinecat h by Oratec on 19 fresh, frozen human lumbar cadaver specimens. In a separa te study, eight specimens were tested biomechanically and instrumented to m ap the thermal distribution, whereas five specimens were tested only biomec hanically, both before and after intradiscal electrothermal therapy. Six ad ditional specimens were heated with intradiscal electrothermat therapy, and the resulting canal was backfilled with a silicone rubber compound to allo w colocalization of the catheter and anular architecture. Results. A consistent pattern of increased motion and decreased stiffness w as observed. For the specimens in which only biomechanical measurements wer e taken, a 10% increase in the motion, on the average, at 5 Nm torque was o bserved after intradiscal electrothermal therapy. No apparent alteration of the anular architecture was observed around the catheter site in the intra discal electrothermal therapy-treated discs. Conclusion. The data from this study suggest that the temperatures develope d during intradiscal electrothermat therapy are insufficient to alter colla gen architecture or stiffen the treated motion segment acutely.