Recently concerns have been raised as to the effect of intra-articular radio-frequency energy on axillary nerve function. In our unit 120 shrinkage procedures have been performed with 5 intra-operative contractions of deltoid and no axillary nerve palsy. In this study we aimed to identify and quantify any changes in axillary nerve function following capsular shrinkage. Needle electrodes were inserted into the deltoid muscle of 10 patients undergoing radio-frequency capsular shrinkage and 3 patients having diagnostic arthroscopy. Recordings of Compound Muscle Action Potentials (CMAPs) were made following pre-operative magnetic coil stimulation of the axillary nerve. The nerve was then monitored during operation. At the end of the procedure, a further recording of CMAP following axillary nerve stimulation was made to allow comparison with initial readings. We have shown:
Low amplitude stimulations of the axillary nerve in 6 of the 10 patients undergoing shrinkage. Increase in latency of the axillary nerve was noted in some patients including the controls. Increase in latency was independent of time spent performing shrinkage. We have concluded:-
Stimulation of the axillary nerve occurs frequently during capsular shrinkage. This axillary nerve stimulation cannot be causally related to the application of radio-frequency energy. Increased latency may occur due to cooling of the nerve by extravasated irrigation fluid. Nerve monitoring is recommended during the training of surgeons new to this technique. We would like to acknowledge the Magstim Company for their assistance with this project.
