Postoperative scapular neck length is associated with strength and rotational range of motion following reverse total shoulder arthroplasty with the Arthrex Univers Revers

Abstract

Background: The purpose of this investigation was to evaluate the impact of scapular neck length (SNL) on outcomes following reverse total shoulder arthroplasty (rTSA) using a lateralized 135° implant (Univers Revers; Arthrex Inc.; Naples, FL). Our hypothesis was that increased postoperative SNL would be associated with improved range of motion (ROM) following rTSA.

Methods: A multicenter retrospective study was performed on a prospectively collected database. Inclusion criteria were patients undergoing primary rTSA with minimum 2-year follow-up. Preoperative radiographs were analyzed for SNL and glenoid height. Postoperative radiographs were analyzed for scapular notching, inferior glenosphere overhang, effective SNL defined as the distance from medial glenosphere to lateral column of scapula (MGLS), lateralization shoulder angle, and distalization angle. Patient reported outcomes, ROM, and strength at 2 years postoperatively were correlated with outcomes controlling for demographic variables. MGLS was stratified by 0-5 mm, 5-10 mm, and >10 mm for analysis.

Results: A total of 485 patients met inclusion criteria for this investigation. Preoperative SNL was negatively associated with external rotational strength at 2 years postoperatively (P = .039), but was not found to influence patient reported outcomes, ROM, or the incidence of scapular notching (P > .05). Increased postoperative MGLS was positively associated with active internal rotation to the highest spinal level (P = .024) and belly press strength (P < .001). Improved abduction strength was observed with MGLS >10 mm (P = .011) and improved belly press strength was observed with a postoperative MGLS of >5 mm (P < .001). Internal rotation was higher in the >10 mm group compared to the 0-5 mm (L3 vs. L4; P < .001). External rotation at 90° was higher in the >10 mm compared to the 5-10 mm group (73° vs. 57°; P = .013).

Conclusion: Increased effective postoperative SNL, or MGLS, is positively associated with rotational ROM and shoulder strength and following rTSA with the Arthrex Univers Revers. Postoperative MGLS of >10 mm is associated with increased Constant strength and belly press strength compared to an MGLS of 0 to 5 mm. The differences in external rotation at 90° in the >10 mm group compared to the 5-10 mm group and for the internal rotation in the 10 mm group compared to the 0-5 mm group met criteria for a substantial clinical benefit.

Keywords: Reverse shoulder arthroplasty; motion; outcome; scapular neck; scapular neck angle; scapular notching; strength.