Thermal profile of radiofrequency energy in the inferior glenohumeral ligament.

PURPOSE

Currently, two different methods of applying radiofrequency (RF) energy (monopolar and bipolar) are available to the surgeon for thermal shortening of the shoulder capsule. The objective of this study was to investigate the temperature changes and the thermal conduction across the human inferior glenohumeral ligament (IGHL) during radiofrequency energy application.

METHODS

Thermistors were secured onto both the intra-articular and extra-articular surfaces of human IGHL. Monopolar RF energy and bipolar RF energy were delivered to the intra-articular surface at the manufacturer's recommended settings. Pre-treatment and post-treatment ligament lengths, widths, heating times, and temperatures were measured and compared.

RESULTS

For the monopolar devices, temperature spikes to 89 degrees C were recorded for the set temperature of 67 degrees C, averaging 77 degrees C +/- 10 degrees C. Temperatures across the ligament averaged 48 degrees C +/- 3 degrees C. For both devices, the IGHL became thicker with higher RF settings. Recorded temperatures decreased as distance increased from the point of application. Maximum temperatures occurred at least 6 to 7 seconds after cessation of energy application.

CONCLUSIONS

The bipolar and monopolar devices had similar conduction times across the ligament, suggesting that this occurs by simple diffusion of heat. Bipolar and monopolar devices were equally efficacious for capsular shrinkage if the extent of the shortening is tightly defined.

CLINICAL RELEVANCE

The thermal probe should not rest in one position for an extended period of time during RF energy application because, as our study showed, the monitoring of temperature or the visualization of tissue change is not efficacious for determining the end point of thermal shrinkage of the shoulder capsule.