Inverted-bearing reverse total shoulder arthroplasty: scapular notching does not affect clinical outcomes and complications at up to 7 years of follow-up.

Abstract

Scapular notching is a common complication of reverse total shoulder arthroplasty (RTSA). Inverted-bearing RTSA (IB-RTSA) systems, with polyethylene (PE) glenospheres and metal or ceramic humeral liners, reduce notching and PE wear compared with traditional Grammont prosthesis designs. However, whether notching after IB-RTSA influences clinical outcomes or complications remains unknown. Therefore, we evaluated the influence of notching on midterm clinical outcomes and complication rates after IB-RTSA. In our prospective multicenter, observational study, patients underwent IB-RTSA, using a prosthesis system with a PE glenosphere and a metal humeral component. We assessed patients clinically for functional scores, active range of motion, and pain and radiographically for notching. Overall, 270 patients (284 shoulders) were treated with IB-RTSA. Of these, 229 shoulders were available for a mean follow-up of 86.7 months (range, 24.0-133.4 months). We observed notching in 35% of shoulders (28% grade 1; 3% grade 2; and 4% grade 3). IB-RTSA led to a distinct type of notching representing the mechanical indent of the humeral component into the scapular neck without PE-induced osteolysis. Patients with and without notching showed similar clinical outcomes (P ≥ .05), complication rates (P = .23), revision rates (P = .87), and survival of implant components after 10 years (P = .85). Midterm results confirmed our hypothesis that patients with notching had equally good clinical outcomes and low complication rates as patients without notching. Additionally, we found a distinct type of notching without signs of PE-induced osteolysis.