Arthroscopic rotator cuff repair is among the most painful of orthopedic surgeries (1-3). Hundreds of thousands of these procedures are carried out in the U.S. each year. Many involve the use of a brachial plexus nerve block, which serves to control pain for 12 to 14 hours. However, when the block wears off, many patients are left with severe pain. (4-5) This severe pain must then be managed at home with oral opioids, which have numerous undesirable side effects, and may lead to chronic opioid dependence. Thus, any therapy which might reduce the pain burden on these patients and therefore reduce opioid use and side effects, would be advantageous.