Histopathological studies in the long-term evaluation of Plastipore prostheses.

Polyethylene sponge (Plastipore TM) prostheses were clinically implanted in the middle ear for periods varying from 2 weeks to 6 years. Revision surgery allowed removal of 98 of these prostheses for histological examinations. Local foreign body reactions and/or microscopic breakdown of the polyethylene were found to varying degrees in 95 of the 98 prostheses. The remaining 3 prostheses showed only fibrous tissue ingrowth without other changes. We compared the histopathology present with the length of time of implantation, and found that the changes noted were more frequent and marked in those prostheses implanted for long periods of time.