Biocompatibility testing of (degraded) PE-PUR foam: Additional testing is still being performed in accordance with ISO 10993 to facilitate a toxicological risk assessment of (degraded) foam particulates, which is relevant if they would potentially contact the patient. This testing includes chemical characterization (i.e., what chemicals may potentially extract or leach from the foam and have direct contact with body tissues and/or fluids), in vitro assessment (i.e., tests performed in a test tube, dish, etc. outside the body), and in vivo assessment (i.e., preclinical testing) of new, lab aged and/or used PE-PUR foam.
To support the assessment of potential genotoxicity, cytotoxicity, and irritation risks of lab-aged foam, chemical characterization of lab-aged foam, as well as experiments to assess the amount of foam that can potentially contact the patient are being conducted, as lab-aged foam did not pass Ames (genotoxicity), cytotoxicity and skin irritation bioassay testing. Further, complementing the lab-aged foam assessment, a chemical characterization of returned/used degraded foam is also being conducted to better elucidate risks under field conditions. Per ISO 10993, the bioassay results cannot stand alone and, therefore, a positive Ames, cytotoxicity, or skin irritation result triggers a required follow-up evaluation including identification of potential confounding factors, and a weight of evidence assessment to determine a confirmed conclusion on potential risks for patients under expected usage of the device.