| Objective:To find proper electrode tip spacing and tip angles of bipolar radiofrequency thermocoagulation(RFTC)treatment in the patients of chronic pain such as discogenic low back pain.Methods:Two 20G(150 mm cannulae lengths,10 mm tip lengths)RF cannula were arranged in the tip spacing of 10 mm,14 mm,18 mm and 22 mm respectively with 0°,30°,60°,90°and 120° on top of a slab of fresh pork liver whose top surface was flat.Temperature of the probes were raised from 65℃to 85℃at a rate of 10℃ every 30 second,and held at 85℃for 180 second.85℃ maintaining 180 second is one cycle.If the core temperature of the heat-lesions not reached 50℃ for 120 second during 4 cycles,these strip-lesions were considered invalid.The tests were repeated 5 times in each group.The geometry of RF heat-lesions are photographed and analyzed.Result:A continuous strip-lesion between two separated bipolar electrode tips was formed,when the tip spacing was 10 mm,14 mm respectively with 0 °,30°,60°,90° and 120 °,18 mm tip spacing with 0°,30° and 60° respectively,and tip spacing is 22 mm with 0°,30 °respectively.The area of lesion under the same tip spacing was two-way correlated to the bipolar angle,the lesion width was positively correlated,and the height of lesion midline was negatively correlated,while under the same bipolar angle,the area,width,andthe height of midline of lesion were positively correlated to the tip spacing.However,no matter how the tip spacing or bipolar angle changes,there is no obvious change in the the distance of outer electrode.In addition,the core temperature of heat lesions can reach 65℃,when the bipolar angle maintained at 0° or 30° with the tip spacing was 10 mm,14 mm,18 mm respectively,60° with 14 mm,18 mm respectively.Conclusion:The following groups can mainly meet the need of bipolar RF treatment of chronic pain such as discogenic low back pain : tip spacing is 14 mm with bipolar angle less than60°,and 18 mm not exceed 30°. |
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