Thursday, February 23, 2012

Acromial base fractures after reverse total shoulder arthroplasty: report of five cases. JSES

Acromial base fractures after reverse total shoulder arthroplasty: report of five cases, a report in the October JSES calls attention to major clinical impact of these fractures and the difficulty in managing them. The problem is clearly demonstrated on this figure from the paper. While the immediate post operative x-rays show the acromion to be intact, the subsequent film on the right shows the fracture displacement with the resulting functional loss of the deltoid origin.

The authors do not discuss how this complication might be avoided - obviously prevention is preferred to treatment.

Our thought is that these fractures result from the fact that the reverse prosthesis abruptly enables loading of the osteopenic acromion that is not used to seeing load due to the preoperative disuse or non-use of the shoulder. Some surgeons using designs such as that shown in the figure above recommend putting the prosthesis in 'tight' to help with stability. In this x-ray one can see how much the arm has been lengthened by this surgery, adding to the tension in the deltoid and the bending load on the acromion.

Our preferred reverse prosthesis (in which we have no financial interest) achieves stability by 'East-West' tensioning as well as by 'South' tensioning, so that it is not necessary to put the deltoid under potentially harmful loads. Theoretically this should reduce the risk of these devastating fractures.


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