Scapular notching in reverse shoulder arthroplasty: is it important to avoid it and how?

BACKGROUND:
Scapular notching, erosion of the scapular neck related to impingement by the medial rim of the humeral cup during adduction, is a radiographic sign specific to reverse shoulder arthroplasty (RSA). Its clinical and radiological consequences remain unclear.

QUESTIONS/PURPOSES:
Therefore, we: (1) determined the incidence of notching in a large series, (2) described the natural history of notching, (3) determined whether notching is related to functional scores or (4) radiographic signs of failure, and (5) identified factors related to notch development.

PATIENTS AND METHODS:
We retrospectively reviewed 448 patients who underwent a Grammont-type RSA (461 shoulders) with a mean followup of 51 months (range, 24-206 months). RSA was implanted for cuff tear arthropathy or osteoarthritis with cuff deficiency. We assessed scapular notching using AP views standardized under fluoroscopy. Clinical assessment included Constant-Murley score and range of motion. Aside from notching, radiographic assessment included evaluation of humeral and glenoid radiolucent lines.

RESULTS:
Notching occurred in 68% of cases. It appeared early, but its later evolution was variable. Notching was associated with followup, strength, passive and active elevation, humeral radiolucent lines, and glenoid lucent lines. It also correlated with a higher rate in patients with preoperative superior erosion.

CONCLUSIONS:
Scapular notching is frequent, generally progresses, and is associated with deterioration of some clinical parameters and radiolucent lines. We believe the preoperative pattern of glenoid erosion is of particular importance due to its influence on the surgeon's glenoid preparation and base-plate positioning. It is crucial to avoid cranial position and superior tilt.

LEVELS OF EVIDENCE:
Level IV, Therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.