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J Shoulder Elbow Surg. 2018 Nov;27(11):1946-1952. doi: 10.1016/j.jse.2018.04.015. Epub 2018 Jun 19.

Instability after reverse total shoulder arthroplasty.

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Department of Orthopaedic Surgery, Stanford University Medical Center, Redwood City, CA, USA. Electronic address:
Department of Orthopaedic Surgery, Stanford University Medical Center, Redwood City, CA, USA.



This study evaluated patients with and without a prosthetic dislocation after reverse total shoulder arthroplasty (RTSA) to identify risk factors for instability.


Dislocation and nondislocation cohorts were established for analysis in 119 patients who had undergone RTSA at our institution between 2011 and 2014. Preoperative history and parameters pertaining to RTSA design were evaluated for correlation with instability. A logistic regression model was used to analyze independent predictors.


Eleven patients (9.2%) demonstrated instability in the early postoperative period. Dislocations occurred at an average of 8 weeks postoperatively (range, 3 days-5 months). The mean follow-up of all patients was 28 months (range, 6-106 months). Postoperative instability was associated with male gender, history of prior open shoulder surgery, and preoperative diagnoses of fracture sequelae, particularly proximal humeral or tuberosity nonunion. Absence of subscapularis repair was an independent predictor of instability. In addition, 5 of the 11 patients (45%) in the instability cohort sustained a second dislocation requiring another operation.


Redislocation after revision surgery for the initial dislocation was an unexpected and alarming finding. Treatment for the initial dislocation event by placement of a thicker polyethylene insert was inadequate in 45% of patients of our cohort and required another revision with a larger glenosphere and thicker humeral inserts. Initial instability after RTSA must be carefully managed, especially in the revision and post-traumatic setting. Exchange to a thicker polyethylene insert only carries a higher risk of recurrent instability.


Reverse total shoulder arthroplasty; complication reverse shoulder; dislocation prosthesis; prosthetic dislocation; prosthetic instability; recurrent instability; revision shoulder arthroplasty

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