What are the instability and infection rates after reverse shoulder arthroplasty?

BACKGROUND: A concern regarding reverse shoulder arthroplasty (RSA) is the possibly higher complication rate compared with conventional unconstrained shoulder arthroplasty. QUESTIONS/PURPOSES: We determined (1) the rate of instability and infection; (2) whether diagnosis influenced instability and infection rates; and (3) whether these complications affect ASES, Constant, and WOOS scores after RSA.
METHODS: A prospective database, clinical charts, and radiographs of 284 patients who had undergone primary (n = 212 patients) or revision (n = 72 patients) RSA were reviewed to identify patients whose postoperative course was complicated by instability or infection.
RESULTS: The rate of instability was similar in patients with primary (eleven of 212 [5%)] and revision (six of 72 [8%]) reverse arthroplasty. The rate of infection was higher in the revision (five of 72 [7%]) than in the primary (three of 212 [1%]) group. Patients with an irreparable subscapularis tendon had a higher rate of instability (14 of 123 [12%]) compared with patients with a repairable subscapularis tendon (one of 161 [less than 1%]). The fracture sequelae group had the highest rate of instability (seven of 25 [28%]) among diagnoses within the primary group. The rates of infection were similar between the diagnoses within the primary group. The improvements in the ASES score, the Constant score, and the WOOS score from preoperatively to postoperatively were better in the no instability/infection group as compared with the instability/infection group.
CONCLUSIONS: This information confirms the available literature allowing surgeons to give patients realistic expectations regarding the infection and instability rates after RSA. LEVEL OF EVIDENCE: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.