Temperature along the axillary nerve during radiofrequency-induced thermal capsular shrinkage

Background: There have been reports of axillary nerve palsy after thermal capsular shrinkage with radiofrequency energy-generating devices. The exact cause of this is unknown. Hypothesis: The temperature of the axillary nerve increases during shoulder capsular shrinkage at various degrees of shoulder abduction. Study Design: Laboratory study. Methods: Fifteen cadaveric shoulders had fiberoptic thermometer probes placed at various points along the axillary nerve and major branches under the capsule. The shoulders underwent thermal capsular shrinkage with a radiofrequency energy-inducing device at various positions of abduction. Results: With the arm at the side, temperatures above 50°C (56°-61°C) were evident along the teres minor branch of the axillary nerve in 4 of 6 specimens. The increase in temperature was noted in the middle to posterior aspect of the inferior capsule. At 45° of abduction, 4 of 5 shoulders demonstrated increases in temperature greater or equal to 50°. Three of 4 shoulders tested at 90° of abduction revealed similar temperature increases, Conclusions: The arthroscopic technique of thermal capsular shrinkage causes an increase in the temperature of the axillary nerve and its branches in 11 of 15 cadaveric specimens tested at various arm positions-particularly affected is the teres minor branch. Clinical Relevance: Orthopaedic surgeons using the radiofrequency device for thermal capsular shrinkage need to be aware of the possible increase in temperature along the axillary nerve and its branches during this procedure. The clinical effect of this type of increase on the nerve is unknown.