Saturday, December 13, 2014

The hazards of a press fit humeral stem in total shoulder arthroplasty

Here's an instructive case. 
The patient had bilateral total shoulder arthroplasties, each of which went on to fail because of rotator cuff rupture and rocking horse loosening of the glenoid component.
The x-rays below show that the on each side the humeral component was placed so that the head was too high in relation to the tuberosity placing extra stress on the cuff tendons and preferentially loading the superior aspect of the glenoid component.

Why did this happen?

The answer is found on the films of the entire humerus, where it is seen that the the distal tip of the prosthesis is wedged in the diaphysis preventing more distal seating. Attempting to drive the stem down further would have risked fracture.

In our practice of revision for failed arthroplasties performed elsewhere we encounter this problem frequently as shown again here.
This problem can be avoided by using a smaller stem along with impaction grafting as shown here.


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