Survivorship of a Medialized Glenoid and Lateralized Onlay Humerus Reverse Shoulder Arthroplasty Is High at Midterm Follow-up

Background: Reverse shoulder arthroplasty (RSA) is a common treatment of a variety of disabling shoulder conditions. The purpose of this study was to determine revision-free survivorship after RSA using a medialized glenoid and lateralized onlay-type humerus implant and to identify etiologies of revision. Methods: All RSAs performed using the Comprehensive^® Reverse Shoulder System (Zimmer Biomet, Inc.; Warsaw, IN, USA) at one institution from 2008 to 2014 were identified through a retrospective review. Charts were reviewed to determine whether the RSA was a primary or revision surgery. Patients were contacted by telephone, and survivorship was defined as no subsequent surgery after RSA. Of the 526 RSAs performed, responses were obtained from 403 patients (77%). A Kaplan–Meier analysis was performed to determine survivorship over time. A χ² test was used to determine differences between revision rates after RSA. Results: Minimum follow-up was 3 years, and average follow-up was 4.83 ± 1.60 years. Survivorship was 96% at 2 years and 93% at 5 years after RSA. Revisions were performed for instability (n = 8), humeral tray-taper junction failure (n = 5), acute fracture (n = 4), infection (n = 3), glenoid loosening (n = 3), osteolysis (n = 1), or notching (n = 1). Fourteen of the 151 patients (9.2%) who had surgery prior to RSA required revision after RSA. Having shoulder surgery prior to RSA was associated with higher rates of subsequent revision after RSA. Conclusion: Overall, survivorship after RSA using a medialized glenoid and lateralized onlay-type humerus RSA is high, and prostheses implanted in native shoulders have lower rates of revision at midterm follow-up. Instability (1.9%) was the most common reason for revision.