Computer tomography assessment of the subscapularis after reverse shoulder arthroplasty and subscapularis repair: reduction in subscapularis size do not affect clinical outcomes

Abstract Background Excellent Clinical and patient-reported outcome have been reported following Reverse Shoulder Arthroplasty (RTSA). However, outcomes in range of motion (ROM) remain variable. The role and importance of subscapularis repair during RTSA is a topic of intense debate and the long term-integrity of the subscapularis after repair remains poorly studied. Aims of this study were to radiologically evaluate pre- and postoperative condition of the subscapularis muscle in RTSA with concurrent subscapularis tendon repair using transosseous suture, and to investigate the correlation between clinical and radiological results. Methods Patients who had undergone RTSA with subscapularis repair in our Institute between January 2010 and November 2016 were included. Constant, UCLA, Simple Shoulder Test and Visual Analog Scale (VAS) pain questionnaires were administered pre- and postoperatively. Internal rotation ability was recorded on a 6-point scale. Pre - and postoperatively shoulder CT scans were performed by a blinded examiner from which subscapularis muscle cross-sectional area (SMCSA) and supraspinatus fossa cross-sectional area (SFCSA) were measured in square millimeters. The SMCSA/SFCSA ratio was employed to standardize values for individual anatomical differences between patients. Results The study included 32 patients (32 shoulders). Mean follow-up was 74.6 months ± 15.2 months (range 35–117 months). Statistically significant differences were found between pre- and postoperative VAS score, Constant Score, UCLA and Simple Shoulder Test scales (P 35% was found in 38% of patients. Only 21% of patients maintained their preoperative SMCSA/SFCSA ratio. Overall, a statistically significant difference in pre and postoperative SMCSA/SFCSA ratios was found (P Conclusion Postoperative subscapularis size expressed as SMCSA and SMCSA/SFCSA ratio, was significantly reduced in the majority of patients treated with non-lateralized RTSA design and concurrent subscapularis tendon repair at final follow-up. A correlation between radiological findings and clinical outcomes was not found. RTSA with subscapularis tendon repair provides a high degree of patient satisfaction, as well as statistically significant improvements in clinical outcomes and internal rotation ROM. Being associated with several advantages, subscapularis repair may be routinely recommended. Level of evidence Level II; Prospective Cohort Design; Prognosis Study