Figure 4.

Non‐particulate Cr accumulates in BM matrix whereas Co was only found in the particulate state and co‐localized with Cr. A) H&E stainings of intertrabecular BM from the proximity of a hip resurfacing implant and a knee endoprostheses. B) Corresponding 2 µm resolved XRF‐maps of intertrabecular BM. The qualitative RGB imaging reveals spacious distribution of Cr and focal hotspots of Co co‐localized with Cr. C) Scatter dot plots of the Co and Cr special mass fractions (areas depicting cancellous bone were excluded, dashed lines) indicate that Co is exclusively co‐localized while Cr is also solitary detected in the BM. D) Scatter dot plots of the Co and P (red) and Cr and P (green) mass fractions indicate distinct co‐localization of Cr with P. E) Scatter dot plots of the Co and S (red) and Cr and S (green) mass fractions indicate distinct co‐localization of Cr with S. F) Cr versus Co mass fractions in P‐ and S‐rich data points by means of the upper 10% of data points regarding their S and P content. (Hip resurfacing: n = 22510 each group, primary TKA: n = 2853 each group; Mann–Whitney test (two‐sided); **** p < 0.001). G) Qualitative RGB imaging of nanoresolved (60 nm) XRF‐maps confirms the distinct deposition of Cr in the marrows’ matrix. Co and Cr containing particles of various sizes and shapes are abundantly represented in peri‐implant BM. H) Quantitative XRF‐heat maps at 30 nm resolution show non‐particulate Cr. Analyses of the according XRF‐spectra clearly demonstrate that the particles consist of both, Co and Cr, whereas areas of non‐particulate Cr do not contain Co. I) Quantification of Co and Cr contents of particles detected in the BM from a knee endoprosthesis (tibial, see (F)), knee endoprosthesis (femoral), hip resurfacing implant and a modular stem hip endoprosthesis (left to right) reveals lower Co:Cr ratios if compared to the bulk alloy. Stated numbers reflect the mass ratios of Co and Cr within the analyzed particles (dashed rectangles). Abbreviation: TKA, total knee arthroplasty.