Instability After Reverse Total Shoulder Arthroplasty: Which Patients Dislocate?

Given the increasing use of reverse total shoulder arthroplasty (RTSA), it is important to study the complications associated with this procedure. We conducted a study of the incidence, predisposing factors, and treatment of RTSA dislocations. Using our institutional database, we retrospectively searched for RTSAs performed between September 27, 2010 and December 31, 2013 and identified postoperative dislocations. Four hundred eighty-seven patients underwent 510 RTSAs (393 primary, 117 revision). Fourteen patients had 15 dislocations (5 in primary RTSAs, 10 in revision RTSAs). Mean time from surgery to diagnosis was 58.2 days (range, 0-319 days). One dislocation occurred immediately after surgery, 2 after falls, 4 from low-energy mechanisms of injury, and 8 without known inciting events. Logistic regression analysis revealed revision RTSA (odds ratio [OR] = 7.515; P = .042) and higher body mass index (BMI) (OR = 1.09; P = .047) to be independent risk factors. The diagnosis of primary cuff tear arthropathy (CTA) was independently associated with a lower rate of dislocation (OR = 0.025; P = .008); dislocation occurred in only 1 (0.35%) of 285 patients with CTA. All dislocations were treated in the operating room; no dislocation was successfully treated with simple closed reduction in the clinic. Although dislocation after RTSA is uncommon, the risk is higher for patients with higher BMI and for revision patients. Patients may benefit from lifestyle modifications, preoperative counseling, intraoperative considerations, and rehabilitation modifications. Patients who undergo RTSA for primary CTA can be reassured that the likelihood of dislocation is low.