Sunday, July 23, 2017

Reverse total shoulder failure from polyethylene dissociation from humeral implant

Polyethylene dissociation from humeral stem status after reverse total shoulder arthroplasty

These authors present four cases of polyethylene liner dissociation from the humeral component of a  reverse shoulder arthroplasty (RSA).  In a series of 549 patients who underwent RSA, the incidence of this complication was 0.7%.  These patients presented with signs, symptoms, and imaging consistent with dislocation but were found to have a dissociation of the polyethylene from the humeral component, rendering a closed reduction impossible.

All four cases were male with a the same implant. The dissociations were recognized between 3 months and three years after surgery. The images from the four cases are shown here. The authors caution, "surgeons should be aware of this possibility if a closed reduction of an RSA dislocation is not possible."

Comment: Because the polyethylene liner of a reverse total shoulder can experience large, non-compressive loads, it is at risk for displacement from the metal humeral cup. Similar complications have occurred with other implants, so it is not clear whether the design of this system is at particular risk for this complication. With any design, it is important that the liner be vigorously and fully seated in the humeral cup after assuring that the cup is dry and free of any interposed tissue. After insertion, the security of the seating needs to be verified.
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