Polyethylene components are prone to wear after long term usage. Instability as well will hasten wear due to abnormal biomechanics. Wear and the subsequent debris that it produces initiate synovitis and foreign body reaction, which can ultimately lead to severe bone loss.
Polyethylene wear is more frequently seen in knee and hip joint replacements due to weight bearing stresses.
In many linked arthroplasty prostheses models, bushings are made of polyethylene. A bushing is defined as a fixed or removable cylindrical lining used to constrain, guide, or reduce friction; in this instance between the humeral and ulnar components.
Bushing wear is determined on an AP radiograph. A line was drawn parallel to the yoke of the humeral component, and another line was drawn parallel to the medial or lateral surface of the ulnar component. An angle of intersection more than 7 degrees indicates excessive tolerance of the bushings due to wear or polyethylene deformation .
|Bushing (red arrow) in linked elbow replacement.|
|Angle of intersection – 9 degrees, consistent with bushing wear|