(Kiosk 2) A Case of Proximal Median Neuropathy After Reverse Total Shoulder Arthroplasty

Case Diagnosis: 72-year-old female with right reverse total shoulder replacement presenting with post-operative right hand weakness.

Case Description or Program Description: A 72-year old female with history of right reverse total shoulder arthroplasty (rTSA) presented to Emory upper extremity clinic with persistent hand weakness 6 weeks after her shoulder replacement. Physical examination revealed difficulty activating her right thumb and index finger flexors and making an “OK” sign. With concern for anterior interosseous nerve palsy, the patient was referred for electrodiagnostic studies.

Setting: EMG clinic

Assessment/Results: Nerve conduction studies of the right upper extremity were notable for reduced median motor compound muscle action potential (CMAP) and absent median sensory nerve action potential (SNAP) amplitudes compared to the left. There was also significantly reduced right median motor conduction velocity in the forearm. Electromyography was notable for positive sharp waves and fibrillation potentials in the right abductor pollicis brevis, flexor digitorum superficialis, flexor pollicis longus, pronator quadratus, and pronator teres, suggesting median neuropathy proximal to innervation of the pronator teres. Repeat electrodiagnostic studies 6 weeks later revealed similar findings. The patient opted to continue with physical therapy given steady improvement of her fine motor function, including thumb flexion.

Discussion (relevance): Classically, proximal median neuropathies can be caused by median nerve entrapment at the heads of the pronator teres, the ligament of Struthers, the lacertus fibrosus, or the flexor digitorum superficialis sublimis bridge. Interestingly, review of the literature demonstrates that reverse total shoulder arthroplasty is associated with high numbers of post-operative nerve complications. Specifically, median neuropathy was demonstrated to be the most common nerve injury after shoulder replacement, though function returned to baseline between 6 and 12 months after replacement.

Conclusions: Nerve complications after shoulder replacement can be attributed to direct nerve damage, excessive traction, and interscalene nerve blocks, among other causes. It is important to recognize post-operative nerve complications, particularly median neuropathy, after shoulder replacement.