Friday, June 29, 2018

Reverse total shoulder - risk of dislocation

Instability after reverse total shoulder arthroplasty

Many designs of reverse total shoulder are now available.

The outcome of the arthroplasty depends not only on the prosthesis, but also on patient characteristics, shoulder characteristics, and surgical technique

These authors evaluated 119 patients with and without a prosthetic dislocation after reverse total shoulder arthroplasty (RTSA) to identify risk factors for instability.

Eleven patients (9.2%) demonstrated instability in the early postoperative period, occurring at an average of 8 weeks postoperatively (range, 3 days-5 months). All dislocations were anterior (see below right).

All failed attempts at closed reduction. The most common preoperative diagnosis for performing a RTSA was rotator cuff tear arthropathy (55%).  

A more horizontal (155°) humeral neckshaft angle and a medialized center of rotation glenoid design were associated with a higher likelihood of stability.

Postoperative instability was associated with male gender, history of prior open shoulder surgery (82%), and preoperative diagnoses of fracture sequelae, particularly proximal humeral or tuberosity nonunion. Absence of subscapularis repair was an independent predictor of instability.

Revision surgery failed in 5 of the 11 patients (45%); these patients sustained a second dislocation requiring another operation.

Treatment for the initial dislocation event by placement of a thicker polyethylene insert was inadequate in 45% of the patients and required another revision with a larger glenosphere and thicker humeral inserts.

Comment: This paper again points to the problem of dislocation after reverse total shoulder arthroplasty. The 9% rate of dislocations requiring revision surgery is a concern.

The majority of these patients received a reverse total shoulder because of cuff tear arthropathy. It is not stated how many of these actually had pseudoparalysis.

Our practice is to offer a CTA prosthesis to patients with cuff tear arthropathy and retained active elevation to avoid the instability risks of a reverse total shoulder. See this link. We have had no instances of dislocation with the CTA prosthesis.

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