HSS Ultrasound of the Month Case 125

Clinical History 71 year old male with new bump along the front of the shoulder several months after reverse shoulder arthroplasty placement.

Ultrasound of the Month – Case 125

1

Ultrasound of the Month – Case 125

Ultrasound of the Month – Case 125

Ultrasound of the Month – Case 125

Diagnosis: Polyethylene Dissociation in Reverse Total Shoulder Arthroplasty.

Instability, including dislocation, is a common complication in reverse total shoulder arthroplasty, reported in 5% of patients.

Polyethylene dissociation occurs much less frequently, but when it does occur, it precludes closed reduction.

The polyethylene liner is not easily visible on radiographs as it is hypodense (dark), unlike the metallic components.

Because the polyethylene is usually positioned between the glenosphere and the humeral component, the two components appearing to be closer together is a radiographic sign of polyethylene dissociation.

On radiographs, the displaced polyethylene liner may be visible as a dark structure surrounded by the more hyperdense (brighter) soft tissues around it.

Ultrasound is another modality which can identify the displaced polyethylene liner if one is familiar with the ultrasound appearance of the liner.

Ultrasound of the Month – Case 125

5