Evaluation of cadaveric lumbar spine temperature distributions during nucleoplasty

Abstract

This study investigated the contribution of applied thermal energy during the nucleoplasty procedure by obtaining temperature maps throughout human cadaveric disc specimens (n=5) during a simulated treatment protocol. The procedure was performed using the ArthroCare SpineWand RF-Coblation device inserted through a 17 g needle into the cadaveric disc. The device uses a dual mode heating technique which employs a high voltage RF plasma field to vaporize tissue, followed by RF current heating for thermal coagulation. The device is manipulated to create a series of 6 channels at a 60 degree angular spacing within a period of 3 minutes. A computer-controlled, motorized translational system was used to mimic the insertion (coblation) and retraction (rf-coagulation) performed during clinical implementation. Rotation was performed manually between each coblation/rf-coagulation cycle. Transient temperature data were obtained using five multi-junction thermocouple probes (5 to 6- 0.05 mm diameter junctions spaced at either 2 or 5 mm) spaced throughout the desired heating volume. Temperature distributions and accumulated thermal doses calculated from the temperature-time history were used to define probable regions of thermal coagulation. Intra-discal temperatures of 60-65C were measured within 2 to 3 mm radial distance from the introducer with therapeutic thermal doses of >250 EM 43C achieved at radial distances of up to 5 mm from the introducer. Although appreciable regions of thermal coagulation within the nucleus are localized around the applicator, improper placement of the applicator during treatment may also generate undesirable hot spots in the bone endplate.