Effect of humeral tray offset on clinical outcomes and computed tomography parameter in reverse total shoulder arthroplasty

Abstract

BackgroundDespite the evolution of reverse total shoulder arthroplasty (RTSA), limitations in range of motion (ROM) and strength leading to limited increases in functional scores have been reported. This study was undertaken to determine the effects of humeral tray lateralization. MethodsA retrospective clinical study was performed on 35 patients who underwent RTSA with a single implant (Aequalis Ascend Flex short stem; Tornier SAS–Wright Medical Inc., Bloomington, MN, USA) and a humeral tray offset of 1.5 mm from July 2016 to November 2020 by a single surgeon. Patients were classified into two groups: an inferiorly positioned humeral tray group resulting in humeral lateralization (the inferior group [n = 22]) and a superiorly positioned humeral tray group resulting in distalization (the superior group [n = 13]). Constant-Murley score, University of California-Los Angeles shoulder scale, Simple Shoulder Test, Activity scale, American Shoulder and Elbow Surgeons shoulder score, and pain visual analog score were evaluated. ROM for forward flexion and abduction was measured. Strengths of forward flexion, internal rotation at 90° abduction, and external rotation at side (ER) were measured. Computed tomography was performed postoperatively to measure the amount of humeral lateralization. ResultsPostoperative ER power was greater in the inferior group (32.39 N ± 12.08 N) than in the superior group (23.77 N ± 10.96 N; P = .043). Postoperative abduction ROM was also greater in the inferior group (158.18° ± 18.36° vs. 128.08° ± 34.97°; P = .011), and humeral tray center to greater tubercle distance was larger in this group (54.68 mm ± 5.31 mm vs. 50.76 mm ± 3.65 mm; P = .025). ConclusionLateralization by inferior humeral tray positioning provided better results than distalization by superior humeral tray positioning in RTSA in terms of ER strength and abduction ROM. RTSA with humeral lateralization appears to result in better functional outcomes in certain conditions.