From a clinical case to a general methodology to analyze prosthetic joint failure, by micro- and nano-characterization with SEM of intra-tissue wear debris

Release of prosthesis debris at the tissue-implant interface is a major cause of aseptic loosening, a phenomenon that requires premature replacement of the prosthesis. The main objective of this paper is to propose a step-structured modus operandi for a reliable scanning electron microscopy (SEM) analysis of debris released from prostheses into the surrounding tissues. Following a proven methodology for the analysis of this wear debris would allow research and hospital laboratories to reduce time and obtain results associated with a common protocol and consequently, more comparable results. For developing the methodology, we chose the clinical case of a hip prosthetic revision, in which a Cr-Co head misalignment caused the wearing out of the polyethylene acetabular insert and a partial wear of the Ti-6Al-4 V acetabular cup. Samples of periprosthetic tissues, after being partially digested in a KOH basic solution, were investigated in vivo and in situ with SEM observations and Energy Dispersive X-rays Spectroscopy (EDXS) analyses. Although developed from a specific case study, this methodology is compatible and applicable to other standard cases as well. Regarding the set of samples we selected, a complete set of micro- and nano-structural analysis, compositional spectra and high-resolution images have been acquired, showing the morphology of the debris involved, and the agglomeration phenomena occurring in the tissue. The proposed protocol complements previous studies on tribological phenomena, underlying debris production at the tissue-prosthesis interface, best digestion techniques for fragment isolation, and nanotoxicology.