Thursday, November 7, 2013

Reverse total shoulder - dislocations soon after surgery

Early dislocation after reverse total shoulder arthroplasty

These authors characterized the patients have a dislocation of a reverse total shoulder within three months of surgery.
Atraumatic instability occurred in 11 patients at an average of 3 weeks. Risk factors appeared to include prior surgery, male sex, obesity, and subscapularis deficiency.
Initial treatment included closed reduction in 9 patients, open reduction in 1, and open reduction with a thicker polyethylene insert in 1. Four experienced recurrent instability requiring a thicker polyethylene insert. Two additional patients were converted to hemiarthroplasty due to persistent instability. 

Importantly, as pointed out in this paper, most of the patients are often unaware of a dislocation. Some report that shoulder pain increased or the shoulder began to feel different after using their shoulder during activities of daily living. Alcohol use and falls can also contribute to the risk of instability.
bed. Two patients admitted to significant alcohol use.

Other series have shown a dislocation rate of up to 10% and have identified unstable prior arthroplasty as the diagnosis with the greatest risk of instability after a reverse total shoulder. Other factors include insufficient soft tissue tension, component malposition, and abutment of the medial aspect of the humeral cup against the scapular neck causing the humeral component to lever away from the glenosphere.

Here is an example - a patient with a history of a fracture treated with a humeral prosthesis. In the process, the tuberosities were lost along with the rotator cuff attachment to the humerus resulting in severe anterosuperior escape.

The patient was treated with a reverse total shoulder that was tight and stable at surgery.
Soon after surgery the patient sustained an atraumatic dislocation.

The shoulder was revised with a thicker polyethylene insert.
Which again dislocated without a traumatic event.
The shoulder was then converted back to a humeral hemiarthroplasty, essentially where the patient started.
This is obviously a very difficult problem, in part because the posterior soft tissues are tight and the anterior soft tissues are frail and weak.

The bottom line is that patients with unstable prior arthroplasties carry an increased risk of instability after a reverse.

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