Revision of the polyethylene component for wear in TKA.

Abstract

Given reports of failure in isolated polyethylene exchange in well-fixed TKA components, we asked whether isolated exchange could be successful either by replacing the polyethylene in implants whose locking mechanism accepts currently available polyethylene designs or by creating a new locking mechanism fabricated with a carbide bit and augmented with polymethylmethacrylate cement. We performed isolated liner exchange for wear in 46 patients (49 knees). The polyethylene locking mechanism in two total knee designs (13 knees) allowed polyethylene exchange without polymethylmethacrylate fixation. A locking mechanism was fabricated for three implant designs (36 knees). Clinical function after polyethylene component exchange was good in all but three knees. No knees with a fabricated locking mechanism failed. The mechanical strength of the fabricated locking mechanism was tested in the laboratory. The cement- fabricated locking mechanism in the unmodified tray notably outperformed the standard polyethylene locking mechanism. Isolated polyethylene component exchange was successful in this small clinical study. Fabricating a locking mechanism with a carbide bit and acrylic cement was effective in laboratory testing and clinical application.