Clinical considerations in the choice of materials for orthopedic internal prostheses.

The six principal clinical considerations which influence the choice of materials for total joint replacements are given. The necessity for screening tests on potentially useful materials is stressed. These should be carried out on specimens which have been exposed to the sterilizing process, which will be used in clinical practice. The materials should also be investigated after immersion in a physiological solution-bovine serum; following implantation in a large animal. Useful tests are impact testing, and wear studies using pin-on-disk and journal and bush specimens. In the case of total joint replacements, equipment in which joint motions and loadings can be simulated can provide valuable information. The components should also be subject to fatigue testing. There is a need to develop agreed laboratory methods for testing of materials and implants and for the long term follow up of patients.