A physical examination of orthopaedic implants and asjacent tissue.

This paper reports a metallurgical study of five metal-on-metal total hip replacements removed from patients because of varying degrees of loss of bone substance and/or proven sensitivity to Ni and Cr. Evidence of corrosion of the Co-Cr-Mo-C alloy used to fabricate the prostheses was found. It is suggested that the products of this corrosion may alter the balance of bone formation/resorption to produce a loss of bone substance. An unusual tissue response which included rod-like particles (1-2 micron long x 0.2 micron in cross section), of possible immunological origin, was seen on examination of the articulating surface of one of the prostheses by scanning electron microscopy.