Opportunities and Challenges of Retrieval Analysis: The Role of Standardized Periprosthetic Tissue and Fluid Analysis for Assessing an Aggravated Host Response

Despite the recent advances with implantable devices, implant longevity and functionality may be compromised by degradative processes such as wear and corrosion, and the implant performance may be further complicated by the resultant host responses. As a window into in vivo implant performance, retrieval analysis is paramount for providing an essential feedback for improving new biomaterial choices and device designs and for securing a decision-making accounting for interindividual variability of real-world performance. Acknowledging the need for leaving the device-tissue interface intact, the current retrieval recommendations (e.g., ASTM F561-13) refer to the importance of proper collecting and handling of the adjacent tissues and fluids so as not to interfere with device/tissue-related analyses or jeopardize patient safety. However, without further stipulation of the utmost importance of comprehensive histopathological assessment, the current retrieval practices remain mostly focused on the mechanical analyses of explanted devices, without sufficiently addressing the corresponding tissue/biofluid changes at microscopic and molecular levels. The recently accumulated evidence on biological responses that comprise implant reactivity provides an impetus for rethinking the retrieval-related potential to enhance our understanding of the implant-elicited host responses and thereby improve preclinical biocompatibility testing and enable more predictive evaluation of in vivo implant performance. The retrieval assessment may be improved by a more detailed characterization of the implant debris in terms of its cellular uptake (e.g., phagocytosability), immune and tissue-destructive responses (e.g., not limited to lymphocyte-mediated alterations), as well as other parameters the implant was exposed to that might affect implant longevity (e.g., mechanical alignment, cement technique, soft tissue support). The revised retrieval practices may help facilitate the Center for Devices and Radiological Health's mission and priorities for building the infrastructure and assessment tools for the National Evaluation System for Health Technology.