Saturday, December 27, 2014

The confusing picture of glenoid component loosening

A man in his late thirties had a total shoulder for arthritis. He had a good result went back to heavy use of his shoulder. He also had a major fall on his shoulder.

He presented to us 12 years later with pain in his shoulder, normal labs and these x-rays.

A surgery the humeral component was well fixed, but the glenoid component was loose. There was a large amount of glenoid osteolysis and a lot of glenoid membrane.

A frozen section was interpreted as showing a foreign body histocytic reaction to wear debris with only rare neutrophils. 

In spite of this apparently benign result, we removed the glenoid and the well fixed humeral component, throughly debrided the reactive tissue, and inserted a new humeral component with Vancomycin allograft impaction grafting according to the red protocol. He was discharged on Ceftriaxone and Vancomycin. In the absence of Mec A positive Coagulase Negative Staph, the Vancomyin was discontinued.

Ten days after surgery, his culture results are as shown below. We will continue to follow the cultures for another week.

It is of interest that his explants had the highest amount of Propionibacterium, possibly because of their location in biofilms.

Is this mechanical loosening, loosening from a reaction to polyethylene debris, or were the Propionibacterium responsible for his osteolysis and glenoid component failure?  Because we are unsure, we're treating this as a Propionibacterium infection.


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