Reference standards for implantable materials: problems and needs

Medical implant materials that come in contact with tissues, body fluids (including blood) constitute an area in medical devices where reliability and clinical performance limitations are vital. Polymeric implant materials differ in important aspects from metals and alloys, and ceramics (including glasses and carbons) with respect to their atomic and molecular structures and morphology. It is suggested that four categories of 'standards' be developed: (1) certified primary reference materials to be used for calibration purposes, (2) reference materials to be used for the comparative evaluation of physico-chemical and biological properties, (3) 'fabrication-grade' reference materials for intercomparative evaluation of processing conditions, and (4) reference implants aimed at the intercomparative evaluation of possible synergistic effects of additives, processing aids, and fabrication processes on in vivo service life, including biological and mechanical performance.