Function after closed reduction from early unstable reverse shoulder arthroplasty

BackgroundOptimizing deltoid tension during reverse shoulder arthroplasty (RSA) remains a challenge for the shoulder surgeon. Ideal tension likely differs based on patient age, anatomy, size, preoperative diagnosis, and deltoid strength. Excess tension might overstuff the joint and limit range of motion. The aim of this study was to compare the function of patients with early postoperative instability (as a proxy for deltoid tension) and those without instability.MethodsA retrospective cohort study comparing two groups of patients with primary RSA operated on over a 5-year period by a single fellowship-trained shoulder and elbow surgeon using a combination of lateralized and medialized glenoid prosthesis with a 135-degree neck-shaft angle on the humeral side was conducted. The main exposure was shoulder dislocation that did not require revision arthroplasty compared with all other patients in the study period who underwent uneventful primary RSA. Chart review was performed for patient demographics, preoperative diagnosis, operative details, preoperative and postoperative range of motion and pain, reoperation, and instability events. The primary outcome was final clinic visit forward elevation. Outcomes included preoperative, postoperative, and difference in forward elevation and external rotation, as well as pain level.ResultsA total of 79 shoulders treated with primary RSA from 2015 to 2019 were identified. The average follow-up was 9 months (range, 3-47 months). Sixty-seven patients (72 shoulders) underwent uneventful primary RSA. Seven patients (7 shoulders) in the treatment cohort presented to a postoperative visit with complaint of shoulder dislocation that was able to be self-reduced and/or presented with a dislocated shoulder requiring closed reduction without sedation. At the final follow-up, average postoperative forward elevation was 121 ± 27 degrees in stable shoulders versus 145 ± 15 degrees in the unstable group (P = .003). No significant difference in external rotation was shown between stable and unstable RSA (39 ± 12 degrees and 36 ± 14 degrees, respectively). Overall average forward elevation and external rotation improved from 71 to 123 degrees and 19 to 39 degrees, respectively. More than 95% of patients (69/72 uneventful RSA and 6/7 unstable RSA) reported improvement in shoulder pain postoperatively.ConclusionIn the absence of other reasons for instability, early dislocation after RSA is a potential marker of relatively loose deltoid tension. In this study, patients with instability demonstrated higher forward elevation. Patients without instability are likely a mix of those with optimal and suboptimal deltoid tension.Level of evidenceLevel III, Retrospective Comparative Treatment Study