What Makes Two Materials “Identical”?

On April 26, FDA released a final guidance on Characterization of Ultrahigh Molecular Weight Polyethylene (UHMWPE) Used in Orthopedic Devices1. The draft of this guidance was issued on February 12, 2016. The guidance addresses four different types of UHMWPE: conventional, highly crosslinked, highly crosslinked containing antioxidants, and non-conventional. The parameters of characterization include material description, sterility, biocompatibility, mechanical properties, and chemical properties. For the base material, FDA “recommends” the inclusion of information on starting resin, resin consolidation method, and the terminal sterilization method. Material properties of interest, depending on the type of UHMWPE, include tensile properties, impact resistance, density, crosslinking parameters, percent crystallinity, melting temperature, fatigue resistance, antioxidants used, effect of antioxidant on wear, creep resistance, and surface durability. These many parameters, and the allowable ranges in relevant standards, demonstrate that material characterization is a complex issue. Yet in the section on biocompatibility, FDA states that “If the subject device uses the identical UHMWPE materials and manufacturing processes as a legally marketed device with a history of safe use, you may reference previous testing experience or literature, if appropriate.” It is not explained exactly what such referen...
Source: MDDI - Category: Medical Devices Authors: Tags: Materials Source Type: news