Clinical outcomes of over-the-top subscapularis repair in reverse shoulder arthroplasty.

Background: Biomechanical research demonstrates increased subscapularis abduction range of motion (ROM) when the tendon's upper two-thirds is repaired over-the-top of the center of rotation during reverse shoulder arthroplasty (RSA). This study compares the clinical outcomes of patients undergoing RSA with over-the-top subscapularis repair (OTTR) to patients without repair.

Methods: We retrospectively reviewed 97 consecutive RSAs with either OTTR of the subscapularis (N = 75) or no repair (N = 22). Repair was attempted in all patients but not performed if the subscapularis could not be brought to the over-the-top position in 20° of external rotation (ER) and 30° of abduction. Improvements in ROM were compared to the minimal clinically important difference for RSA.

Results: The mean follow-up was 3.8 ± 1.6 years. Demographics were similar between groups. Preoperatively, patients undergoing repair had greater ER when compared to those without repair (15 ± 16° vs. 5 ± 12°,  = .003). Postoperatively, patients undergoing repair had greater forward elevation (132 ± 21° vs. 126 ± 22°,  = .268) and abduction (114 ± 26° vs. 106 ± 23°,  = .193) with both exceeding the minimal clinically important difference (-2.9° and -1.9°, respectively); however, not statistically significant. Patients with repair were more frequently able to reach the small of their back postoperatively (65% vs. 21%,  = .006) but had less improvement in ER (13 ± 20° vs. 24 ± 20°,  = .028). Postoperative outcome scores, complications, and reoperations were similar between groups.

Discussion: OTTR of the subscapularis in RSA had similar ROM and outcome scores compared to no repair, but a significantly larger proportion of patients with repair achieved functional internal rotation to the small of the back. ER limitations seen after conventional repair may also apply to this novel technique, but without a corresponding detrimental effect on forward elevation or abduction.