Does Correction of Reverse Shoulder Arthroplasty Angle by Asymmetrical Glenoid Reaming Reduce Scapular Notching?

Background Scapular notching (SN) is a unique complication of Grammont-type reverse shoulder arthroplasty (RSA). Avoiding superior inclination of the glenoid component is one of several strategies proposed to minimize the incidence of SN. Preoperative measurement of glenoid inclination across the entire glenoid surface may underestimate the potential superior inclination of the RSA baseplate, which is typically implanted in the inferior part of the glenoid fossa. Therefore, a specific RSA angle was introduced. Materials and methods A two-center retrospective study was conducted in 121 patients treated with a primary Grammont-type reverse shoulder arthroplasty between January 2018 and December 2022, with a mean radiographic follow-up of 4.1 years (range, 2–5.9 years). Global glenoid inclination, as well as preoperative and postoperative RSA angles, were measured on plain anteroposterior shoulder radiographs. Scapular notching was assessed according to the Sirveaux classification. Results The mean global glenoid inclination was 11° ± 6°, and the mean preoperative RSA angle was 17° ± 6°. Scapular notching was observed in 36 shoulders (29.75%). Patients with SN had a statistically significantly higher postoperative RSA angle (17° ± 5°) than patients without SN (5° ± 5°) ( p < 0.001). Patients without SN demonstrated a significantly greater change from preoperative to postoperative RSA angle (12° ± 5°) compared with patients with SN (6° ± 5°) ( p < 0.001). Conclusion The inclination of the inferior part of the glenoid fossa is variable and significantly higher than the global glenoid inclination. Insufficient correction of glenosphere inclination by asymmetrical glenoid reaming in medialized Grammont-type RSA is associated with a higher incidence of scapular notching, and measurement of the RSA angle during preoperative planning may be recommended.