Glenoid-sided lateralization decreases scapular notching with a 135° humeral component Arthrex reverse shoulder arthroplasty.

BACKGROUND

The incidence of scapular notching has dramatically reduced with the shift from 155° to 135° humeral inclination in reverse shoulder arthroplasty (rTSA). However, humeral inclination is not the only factor as notching persists with medialized glenospheres. The purpose of this study was to assess the effect of glenoid-sided lateralization on scapular notching with a 135° rTSA.

METHODS

A retrospective review was performed from a multicenter prospectively collected database to identify patients who underwent primary rTSA and had a minimum 2-year follow-up. All rTSAs were performed with the Arthrex system using a 135° inlay humeral component. Varying amounts of glenoid-sided lateralization were used from 0 to 8 mm in 2-mm increments based on surgeon preference. Postoperative radiographs were evaluated for scapular notching, distalization shoulder angle, and lateralization shoulder angle. The lateralization shoulder angle was further subdivided into humeral and glenoid contributions. Regression analysis was performed on component and clinical variables to assess for factors predictive of notching and the effect on clinical outcomes.

RESULTS

Overall, scapular notching was observed in 56 of 517 shoulders (10.8%). Metallic glenoid lateralization and glenosphere overhang were protective of notching (P = .030 and P = < .001, respectively). For women, 6 mm of lateralization reduced notching compared to 4 mm or less (5.3% vs. 15.6%; P = .016). For men, 8 mm of lateralization reduced notching compared to 6 mm or less but the difference did not meet statistical significance (7.6% vs. 13.6%; P = .161). Notching also was associated with decreased forward flexion by 13° (β -12.79, 95% confidence interval: -19.63 to 5.96 P = < .001).

DISCUSSION: With a 135° inlay humerus and lateralized glenoid rTSA, scapular notching decreases with metallic lateralization of 6 mm or more. Additionally, inferior glenosphere positioning is protective of notching. Notching is associated with worse clinical outcomes and lower postoperative range of motion.