Axillary nerve temperatures during radiofrequency capsulorrhaphy of the shoulder

Purpose: The purpose of this study was to determine the temperatures along the course of the axillary nerve during radiofrequency (RF) capsulorrhaphy of the shoulder in a cadaver model. The hypothesis of this project was that temperatures capable of damaging neural tissue would be recorded during simulated RF capsulorrhaphy. Type of Study: Basic science evaluation. Methods: This study used 9 fresh-frozen cadaver shoulder capsules removed en bloc along with the underlying axillary nerve and soft tissue. The axillary nerve was instrumented with 4 thermocouples placed along the course of the nerve (2 thermocouples anterior and 2 posterior to the 6 o'clock position, spaced 7 mm apart). Each of the specimens underwent RF thermal capsulorrhaphy during which the temperature at each of the thermocouple positions was continuously recorded. Results: The average of the maximum temperature at each of the 4 positions measured along the course of the axillary nerve were 52.2 +/- 18.0 degreesC at the most anterior place probed, 45.8 +/-5.44 degreesC (mid anterior), 44.5 +/-8.7 degreesC (mid posterior), and 42.8 +/- 10.1 degreesC at the most posteriorly positioned probe. Two specimens had a maximum temperature greater than the 67 degreesC set point of the device, and 7 specimens had a maximum temperature greater than 45 degreesC in at least 1 thermocouple position. Conclusions: This study shows that heating of the axillary nerve can occur during RF capsular shrinkage of the shoulder and may potentially reach levels that can damage neural tissue.