Radiographic parameters associated with excellent versus poor range of motion outcomes following reverse shoulder arthroplasty.

Background: The purpose was to evaluate the relationship of component size and position to postoperative range of motion following reverse shoulder arthroplasty. The hypothesis was that increased lateralization, larger glenospheres, and a decreased acromiohumeral distance would be associated with excellent postoperative range of motion.
Methods: A retrospective multicenter study was performed at a minimum of one year postoperatively on 160 patients who underwent primary reverse shoulder arthroplasty with a 135° humeral component. Outcomes were stratified based on postoperative forward flexion and external rotation into excellent ( n  = 42), defined as forward flexion >140° and external rotation > 30°, or poor ( n  = 36), defined as forward flexion <100° and external rotation < 15°. Radiographic measurements and component features were compared between the two groups.
Results: A larger glenosphere size was associated with an excellent outcome ( p  = 0.009). A 2-mm posterior offset humeral cup ( p  = 0.012) and an increased inferior glenosphere overhang (3.1 mm vs 1.4 mm; p  = 0.002) were also associated with excellent outcomes. Humeral lateralization and distalization were not associated with an excellent outcome. Conclusion: L arger glenosphere size and inferior positioning as well as posterior humeral offset are associated with improved postoperative range of motion following reverse shoulder arthroplasty.
Level of Evidence: Level 3, retrospective comparative study.
Competing Interests: Declaration of Conflicting Interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: PJD is a paid consultant for and receives royalties from Arthrex, Inc. PJD and GH, their immediate family, and any research foundation with which they are affiliated did not receive any financial payments or other benefits from any commercial entity related to the subject of this article. AL is a paid consultant for Arthrex, Wright, and Medacta and receives royalties from Wright. RUH is a paid consultant for Arthrex, Inc. BOP, ESL, and JMT are paid consultants for and receive royalties from Arthrex, Inc.
(© 2020 The British Elbow & Shoulder Society.)