Scapular Notching after Reverse Shoulder Arthroplasty Does Occur and Adversely Affects Outcomes

Objectives: Reverse shoulder arthroplasty (RSA) is increasingly used for rotator cuff arthropathy, glenohumeral arthritis, and irreparable rotator cuff tears. Scapular notching, erosion of the inferior scapular neck from prosthetic impingement, is graded using the Nerot-Sirveaux classification. This study aimed to determine the incidence and severity of scapular notching after RSA in an Asian population, identify factors predictive of its occurrence, and evaluate its effect on functional outcomes. Age, sex, glenoid height, and implant neck-shaft angle were assessed as candidate predictors given their influence on glenosphere positioning and impingement risk. Material and Methods: This was a retrospective cohort study of all patients who underwent primary RSA at a single institution by a single surgeon between January 2011 and December 2019 (IRB-approved; consent waived). Patients with rotator cuff arthropathy, primary glenohumeral osteoarthritis, post-traumatic glenohumeral arthritis with rotator cuff tear, or humeral head avascular necrosis were included; those with fracture non-union, malunion, or revision RSA were excluded. In total, 142 shoulders in 137 patients (5 bilateral) met these criteria and were analyzed, with 1-year follow-up. Post-operative radiographs were graded for notching using the Nerot- Sirveaux system, and outcomes were compared using the Constant, UCLA, and Oxford Shoulder scores and range of motion. Results: Scapular notching occurred in 25 of 142 shoulders (17.61%; 95% CI, 11.73%-24.88%) within 1 year (Grade 1, n=14; Grade 2, n=6; Grade 3, n=4; Grade 4, n=1). Notching was not significantly associated with age, sex, glenoid height, or implant neck-shaft angle; 1-year forward flexion and abduction were similar between groups. At 2 years, shoulders without notching had significantly better median Constant ( p <0.001), UCLA ( p <0.046), and Oxford Shoulder ( p <0.001) scores than those with notching. Conclusion: Scapular notching occurred in approximately 1 in 6 shoulders after RSA in this Asian cohort. While it did not affect early range of motion, notching was associated with significantly poorer functional outcomes at 2 years, supporting strategies to minimize its occurrence.