Morphological and Analytical Studies of the Tissues Adjacent to Joint Prostheses: Investigations into the Causes of Loosening of Prostheses

Abstract

Loosening of the prosthesis, an important cause of clinical failure following total joint replacement, may be due to faulty implantation of the prosthesis, to trauma, or to infection in the tissues adjacent to the implant. Many cases of loosening exist, however, in which the technique of implantation appears to have been satisfactory, in which there is no history of injury, and in which there is no evidence by conventional criteria of the presence of infection. Moreover, the very good results which are generally obtained immediately following total joint replacement are, regrettably, no guarantee of permanent success in the long term. Thus even if a prosthesis is firmly fixed for a short or long period after implantation, various factors can eventually lead to loosening at a later date. Clearly, at the forefront of any discussion of the causes of late prosthetic failure must be the consideration of the possible sequelae of the interaction between the body tissues and the implant materials used. It is for this reason that the biological reactions to implant materials have been actively studied in a number of centres in recent years. This chapter will attempt to review the findings in the light of current knowledge with particular regard to:

• 1. loosening of the bond between cement and bone,

• 2. reactions of the tissues to the products of wear and corrosion,

• 3. hypersensitivity to implant materials as a cause of prosthetic failure, and

• 4. 4. the implications regarding the future design of prostheses, techniques of implantation, patient selection, and the early detection and treatment of late prosthetic failure.