INTRODUCTION: The final cleaning afterfabrication of medical devices is becomingmore and more important. Based on thebackground of the 4th amendment of theMedical Device Directive, the validation ofcleaning processes has become moresignificant, so that the notified bodiesincreasingly demand proof of the chemicalcleanliness and absence of particles on productsurfaces. Against this background the NMI hascarried out an industrial joint research projectin cooperation with 22 implant manufacturersfrom Germany and Switzerland with theobjective of a qualitative entire as well asquantitative and therefore objective validation of chemical cleanliness of implant surfaces.
METHODS: Characteristic implant surfaces made from material grades like titanium,stainless steel and CoCrMo were contaminatedwith auxiliaries used in the fabrication andwere subjected to a standardized cleaningprocess. Afterwards the cleaned surfaces werecharacterised with interface- andmicrostructural analysing technologies. Theexaminations were focused on X-rayphotoelectron spectroscopy (XPS) and scanningelectron microscopy (SEM).
RESULTS: The examinations offered thechemical composition and surface structures ofaccepted clean surfaces according to the currentstate of the practice in fabrication of medicalproducts on multiple of common implantmaterials in medical technologies andespecially in implantology. The analyses yield the concentration of everychemical element (except hydrogen andhelium) and the chemical compounds ofresidues on the surface, but also potentialchanges in chemical composition. Furthermorethe structure of the surface of the materialgrades itself was examined.
DISCUSSION & CONCLUSIONS: According to the used analysis methods, it hasbeen concluded that residues of the fabricationcould be identified and also quantifiedconcerning their entire complexity. In contrast to other methods like OPA, TOC,GC, IR etc. all chemical elements andcompositions can be detected. In addition theexaminations are carried out directly on thesurface. XPS analysis in contrast avoids typicaluncertainties of elution methods such as thepossible incomplete ablation and, therefore,incomplete analysis of the contaminations. The compiled results are building the basis forthe generation of our XPS standard surfaces.These are used for an objective benchmarkingfor the cleanliness of implant surfaces and alsoother medical products. Hence XPS standardsurfaces by now are suitable within theframework of the approval of medical devicesand quality assurance in fabrication processes.Moreover the use of our analysis methodsprovides information about the material surfaceitself, particularly with regard to theirfunctionality. In comparison to the documentedstructures of new products a benchmarking ofthe functionality of corresponding reprocessedproducts with idem product numbers can be conducted.
REFERENCES: B. Oppermann (2008)Chemische Sauberkeit sicher nachweisen -auch ohne Normen; medizin & technik, 04: 4041.