Review Question - QID 217369

This patient suffered a nerve injury during glenoid exposure and preparation of a reverse total shoulder arthroplasty (RSA). The most commonly injured nerve during this step of the procedure is the axillary nerve (B).

RSA is a type of shoulder arthroplasty that uses a convex glenoid hemispheric ball and a concave humerus articulating cup to reconstruct the glenohumeral joint. The center of rotation is moved inferiorly and medialized which allows the deltoid muscle to act on a longer fulcrum and have more mechanical advantage. One known complication following RSA is neuropraxia. Neurapraxia of the axillary nerve has a reported incidence 0.5-1%. Some cited risk factors include the use of an anterosuperior approach since adequate exposure requires retraction of the deltoid muscle, with a tendency to lever on these. Humeral lengthening is also a cited cause of axillary neuropraxia. Treatment is most commonly observation as the majority of these neurapraxias are transient.

Shinagawa et al. reviewed the risk of nerve injury with neuromonitoring during RSA. They reported that the axillary nerve was associated with the most amount of alerts during the glenoid preparation portion of the procedure. They concluded that the axillary nerve was the nerve most frequently exposed to the risk of injury, especially during glenoid and humeral implantation.

Lädermann et al. prospectively reviewed the subclinical prevalence of neurologic lesions after total shoulder arthroplasty. They reported that electromyography performed at a mean of 3.6 weeks postoperatively in the RSA group showed subclinical electromyographic changes in nine shoulders, involving mainly the axillary nerve; eight resolved in less than six months. They concluded that the occurrence of peripheral neurologic lesions following RSA is relatively common, but usually transient and that arm lengthening with an RSA may be responsible for these nerve injuries.

Figure A is the unlabeled brachial plexus. Illustration A is the corresponding labeled brachial plexus.

Incorrect Answers
Answer 1: This is the radial nerve.
Answer 3: This is the musculocutaneous nerve.
Answer 4: This is the median nerve.
Answer 5: This is the ulnar nerve.