Is subscapularis repair beneficial in patients undergoing reverse shoulder arthroplasty for glenohumeral osteoarthritis with an intact rotator cuff: evaluation of a treatment protocol?

Reverse total shoulder arthroplasty (rTSA) is an alternative to anatomic total shoulder arthroplasty for the treatment of primary glenohumeral osteoarthritis (GHOA) with intact rotator cuff. The utility of subscapularis (SC) repair in rTSA remains controversial. The purpose of this study was to investigate the effect of an SC repair treatment protocol on the outcome of rTSA for treating GHOA with an intact rotator cuff using a lateralized glenoid and inlay humerus rTSA system (Enovis/DJO RSP and AltiVate). This was a retrospective study of 80 patients with GHOA and intact rotator cuff who underwent rTSA with a lateralized glenoid and inlay humerus design. SC repair was performed in 50 patients (62.5%) when it did not limit intraoperative passive external rotation (PER). Outcomes were assessed at a minimum of 1-year follow-up. Mixed effects models assessed associations between SC repair and patient-reported outcome measures (PROMs), internal rotation activities of daily living (IR-ADL), range of motion (ROM), and strength. There were no differences in the characteristics of the repaired and unrepaired groups. At minimum 1-year follow-up, there were no significant differences in the PROMs between the repaired and unrepaired groups. However, the repair group had significantly better PROMs at the 3- and 6-month follow-up. The repair group had greater mean preoperative active external rotation (AER) (11.9° ± 20.0° vs. -1.3° ± 23.1°, P = .017). There was no difference in postoperative mean AER (32.5° ± 15.3° vs. 31.2° ± 13.6°, P > .99). The no repair group had greater improvement in AER (32.5° ± 20.5° vs. 20.8° ± 20.7°, P = .032). The repair group had significantly greater internal rotation (IR) ROM and strength at all follow-ups. A greater proportion of patients in the repair group achieved the patient acceptable symptom state (PASS) for IR ROM (93.8% vs. 75.9%; P = .024), whereas a greater proportion of the unrepaired group achieved substantial clinical benefit (SCB) for AER (90.0% vs. 60.4%, P = .005). Although there were no differences in IR-ADLs at 1-year minimum follow-up, the repair group was better at the 3- and 6-month follow-ups. There were no cases of instability. There are trade-offs to SC repair in rTSA for patients with GHOA and intact rotator cuff. Selective SC repair was associated with greater early outcomes without meaningful PROM differences at minimum 1-year follow-up. However, SC repair that does not limit intraoperative PER results in better IR motion and strength compared with cases in which repair without limiting PER ROM is not possible. On the other hand, if SC repair limits PER, foregoing repair improves AER ROM without affecting PROMs or stability.