Does Subscapularis Repair Influence Range of Motion After Reverse Shoulder Arthroplasty With a Lateralized Glenosphere?

Background The role of subscapularis repair in reverse shoulder arthroplasty remains controversial, particularly with contemporary glenoid designs that lateralize the center of rotation. This study compared early postoperative range of motion in patients undergoing reverse shoulder arthroplasty with and without subscapularis repair using a single prosthetic platform with a lateralized glenosphere. Methods This retrospective, comparative, single-center study included 66 patients who underwent primary reverse shoulder arthroplasty between January 2021 and December 2025 using the same prosthetic platform (Implantcast GmbH, Buxtehude, Germany) with a lateralized glenosphere and a 135° humeral neck-shaft angle. Forty-four patients underwent subscapularis repair and 22 did not. Active and passive elevation, external rotation, and internal rotation were assessed at three and six months postoperatively according to the standardized method of the American Shoulder and Elbow Surgeons. Between-group comparisons were performed for each range-of-motion variable at each time point, and paired observations were used to assess changes from three to six months. Twelve between-group comparisons were performed; the analysis was exploratory, no outcome was designated as primary, and Holm-adjusted p values are reported as a sensitivity analysis. Results At three months, passive external rotation was greater in the group without subscapularis repair (67.08 ± 12.15° vs. 57.65 ± 10.33°; difference -9.44°, 95% CI -18.03 to -0.85; p = 0.033). At six months, active internal rotation was greater in the repair group (median L1/T12 vs. L1; p = 0.023). Neither difference retained statistical significance after Holm-Bonferroni adjustment (adjusted p = 0.358 and 0.281, respectively). No other between-group difference was observed at either time point. Active elevation improved from three to six months in both groups (+19.5°, 95% CI +8.5 to +30.5 in the repair group; +29.1°, 95% CI +8.2 to +50.0 in the non-repair group), while within-group changes in internal rotation did not reach statistical significance in either group. Conclusions In this retrospective, non-randomized cohort, subscapularis repair was associated with nominal differences in early postoperative rotation after reverse shoulder arthroplasty with a lateralized glenosphere. Greater active internal rotation was observed at six months in the repair group, whereas greater passive external rotation was observed at three months in the non-repair group; however, neither finding remained statistically significant after adjustment for multiple comparisons. No overall range-of-motion advantage was identified for either strategy. These exploratory observations should be considered hypothesis-generating and require confirmation in adequately powered prospective studies.