Review Question - QID 213963

This patient underwent a reverse shoulder arthroplasty (RSA) with superiorly tilted glenoid components. This patient is most at risk for scapular notching.

RSA has several clinical indications and its biomechanical advantage relates to the placement of the center of rotation (COR) medially and inferiorly, allowing the deltoid muscle to act on a longer fulcrum to substitute for rotator cuff muscle insufficiency. Scapular notching is a common complication following RSA. It is related to the impingement of the medial rim of the humeral cup during shoulder adduction. Risk of scapular notching is increased with a superiorly placed glenoid component, or insufficient inferior tilt of the glenoid component. Inferior tilt, inferior translation, and lateral offset have all been found to be protective of this finding.

Friedman et al. reviewed the clinical importance of notching and treatment options and reported that the incidence and severity of scapular notching is related to prosthetic design and surgical technique. They found that scapular notching may lead to deterioration of functional outcomes and glenoid implant loosening and failure. They concluded that lateral offset, inferior glenosphere overhang, and careful consideration of the presurgical glenoid morphology may help prevent scapular notching.

Li et al. retrospectively reviewed the incidence of notching with an eccentric glenosphere in 82 patients. They found the overall presence of notching was 11% and was correlated to the amount of inferior offset. They concluded that an inferior offset glenosphere reduced the incidence of scapular notching in RSA.

Figure A is the AP radiograph demonstrating an RSA with superiorly tilted glenoid components. Illustration A is the classification of scapular notching following RSA.

Incorrect Answers:

Answer 1: Acromion fractures are feared complications following RSA. They occur following a fall and have been associated over-tensioning the RSA components
Answer 2: Glenoid baseplate failure is a serious complication following RSA, but much less common than scapular notching with superiorly placed glenoid components in RSA
Answer 3: Glenosphere disassociation is rare. It may be secondary to intraoperative failure of engaging the glenosphere to the baseplate
Answer 4: Periprosthetic humeral stem fracture would not be a significant complication related to superiorly placed glenoid components in RSA