Mechanism for Proximal Median Neuropathy as a Complication of Reverse Shoulder Arthroplasty: Nerve Strain Calculated from a Computerized 3-D model Cadaver Brachial Plexus (P2.016)

BACKGROUND: Reverse total shoulder arthroplasty (RSA) received FDA approval for rotator cuff-tear arthropathy and has been shown to provide pain relief and improve function. RSA is a shoulder replacement procedure wherein there is a reversal of the physiological ball (humeral head) and socket (glenoid fossa of the scapula). The result is distal displacement and medialisation of the centre of rotation of the shoulder joint, increasing the lever arm of the deltoid and also allows more recruitment of deltoid muscle fibers for shoulder elevation and abduction. Its use has become popular even though with a high major complication rate. We present a case of proximal median neuropathy as a consequence of reverse shoulder arthroplasty. PATIENT: This is a case of a 72-year-old, left handed lady working as an artist painter, who underwent a left reverse total shoulder surgery for a massive rotator cuff tear injury. After 10 days following surgery, she developed left hand grip weakness, hot, burning and tingling sensation radiating particularly to the thumb, index and middle fingers. At 1 month postoperatively, a needle electromyography (EMG) study showed severe left proximal median mononeuropathy at/above origin of the branch to pronator teres muscle. OUTCOME: The mechanism of injury of the median nerve can be isolated to traction injury. Demonstrated on an in vitro cadaver brachial plexus computerized 3D model that successfully calculated the strain and measured nerve displacement before and after placement of reverse shoulder prosthesis (Van Hoof et al). Results showed that the medial (19.3[percnt]) and lateral (15.3[percnt]) root of the median nerve are far more strained than any other parts of the brachial plexus. CONCLUSIONS: To the authors’ best knowledge, this case is the first report of a proximal median mononeuropathy arising from reverse shoulder arthroplasty. Future design modifications should consider reducing the strain on the brachial plexus. Disclosure: Dr. See has nothing to disclose. Dr. Katirji has nothing to disclose. Dr. Preston has nothing to disclose. Dr. Shapiro has received research support from Actelion Pharmaceuticals.