Axillary Nerve at Risk
Axillary Nerve at Risk
Abstract & Commentary
Synopsis: Radiofrequency probes can deliver temperatures in excess of safe levels to the axillary nerve despite being used in a recommended manner.
Source: Gryler EC, et al. Arthroscopy. 2001;17(6):567-572.
Radiofrequency and laser energies are methods designed to apply thermal energy to tissues. Radiofrequency uses either a monopolar or bipolar probe tip to deliver the low-frequency energy. Application of radiofrequency to injured tissue is a common procedure performed by arthroscopic surgeons to tighten loose shoulder capsules. However, the axillary nerve is in close proximity to the capsular tissues heated during surgery and temperatures as low as 47°C can injure a nerve in animal studies. Therefore, the purpose of this study was to measure temperatures in the axillary nerve of cadavers.
Shoulder capsule tissue was dissected in 9 fresh cadaver specimens and thermocouplers were placed along the axillary nerve. The Oratec ORA-50 generator with a temperature setting of 67°C, power setting of 40 W, and a wheel selector of 5 was used for testing. A slow, constant, medial-to-lateral pattern of wand direction was used to treat the entire capsule. The speed of movement of the wand was based on observing visual changes in the capsule.
The histologic results identified that the capsular tissue was contracted and slightly hyalized. The temperature readings identified 5 specimens that had a thermocoupler temperature greater than 45° for 10 seconds, and 3 specimens that had temperatures greater than 50° for 10 seconds. Two specimens had transient spikes greater than 67°.
Comment by James Slauterbeck, MD
I was impressed with the response to a commentator’s question posed at a sports medicine meeting where the audience replied that more than half of the participants have noted axillary nerve sensory changes in patients after radiofrequency treatment. Additionally, 2 surgeons stated that they have had patients with mild motor weakness for longer than 6 months. The prolonged elevated temperatures in this study may explain why surgeons are experiencing these complications.
Radiofrequency is a relatively young technique to treat loose capsules during arthroscopy. Several methods have been advocated to decrease complications from excessive energy application. These methods center on the timing of energy application to the capsule (speed of wand movement) and pattern of application (checkerboard, paintbrush, entire capsule, avoiding 6 p.m. position, etc.).
After reviewing this article I am more cognizant of the fact that the probe tips may not accurately measure tissue temperature. Therefore, I recommend that one makes sure adequate flow is present in the shoulder, one uses a consistent, appropriate wand, and one never reapplies radiofrequency to already treated tissue. We need to respect temperatures in the heating of the shoulder capsule so that we do not create a worse problem in the long run in these injured athletes.
Dr. Slauterbeck, Associate Professor, Department of Orthopedic Surgery, Texas Tech University Health Sciences Center, Lubbock, TX, is Associate Editor of Sports Medicine Reports.
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