Effects of thermal therapy on intervertebral discs: investigations using a miniaturized RF heating probe in a small animal model

摘要

Several studies have suggested that thermal therapy has a beneficial effect on degenerated intervertebral discs.Possible therapeutic mechanisms include collagen denaturation, cell ablation, and nerve tissue coagulation, howeverthe precise mechanism or combination of mechanisms is unknown. To investigate the in vivo effects of thermaltherapy on intervertebral discs using a murine model, a monopolar RF heating probe was developed and characterized.In addition, the effect size of several different thermal exposures was investigated by quantifying regions of cell deathand collagen denaturation in rat discs. The heating probes were fabricated to have a 0.3mm outer diameter, 0.9mmexposed heating tip, and contain a thermocouple to monitor probe temperature. Using less than 2 Watts of RF energyproduced high temperatures close to the probe and a steep radial temperature falloff. Five discs were treated at each ofseven thermal exposures: 80ºC for 10min, 80ºC for 1min, 75ºC for 5min, 62ºC for 10min, 55ºC for 15min, 48ºC for15min, and 48ºC for 5min. A cell death region was observed in all treated discs and was significantly greater at the80ºC for 10min exposure than any of the lower exposures. Denaturation area was significantly greater at the 80ºC for10min exposure than at the four lowest temperature exposures. Denaturation was not observed in the 48ºC exposuresand was inconsistent in the 55ºC and 62ºC exposures. These results demonstrate that it is possible to limit and targetthe effects of thermal therapy to a portion of the murine disc using this RF probe.