Adrian Buchholz

It has been shown that the incorporation of silver into the surface of a titanium alloy (Ti6Al4V) by powder mixed electrical discharge machining (PMEDM) exhibits an antiadhesive effect against Staphylococcus spp.. This study aims to investigate the electrochemical performance of this modified surface under simulated physiological conditions, mimicking in vivo corrosion-inducing conditions. Electrochemical behavior was analyzed using potentiodynamic polarization measurements, Kelvin probe fore microscope (KPFM) measurements and ion release quantification, while crevice-corrosion mechanisms were evaluated retrospectively by scanning electron microscopy and energy-dispersive X-ray spectroscopy.Corrosion current density showed an inverse association with PMEDM discharge energy, while neither silver content in the modified zone nor the open-circuit potential exhibited a significant association with corrosion activity. Crevice exposure led to Ti-rich, O-poor deposits at the inner end consistent with hydride formation and localized Ag-associated microgalvanic pitting corrosion were observed; which could be confirmed by local Volta potential differences in KPFM measurements. However, no widespread material degradation or propagating crevice corrosion was observed under the investigated conditions. Metal quantification revealed higher absolute release of alloying elements from the rougher PMEDM surfaces and an increase in the Ag release with the Ag content on the surface; the measured released Ag levels were within ranges regarded as antibacterial.Together, these findings indicate that PMEDM processing parameters influence the global electrochemical response, whereas Ag (particles) primarily affect localized surface mechanisms and Ag ion release. Under the investigated conditions, no correlation between Ag and corrosion current nor widespread surface degradation was detected, which could be translated into independent adaptation options for both electrochemical performance (based on discharge energy) and antibacterial properties (based on Ag content).

This study compares CoCrMo particles generated by a high-energy ball milling method with those produced by the established Buchhorn method and with in vivo-generated wear particles from periprosthetic tissue. CoCrMo particles were produced utilization both methods. The particle size distribution was analyzed using laser diffraction, and the morphology was examined through scanning electron microscopy (SEM). Energy-dispersive X-ray spectroscopy (EDS) provided a qualitative analysis of the material composition. The high-energy ball milling method yielded CoCrMo particles with a D50 of 7.92 µm, a significantly smaller value than the D50 of 88.30 µm observed for Buchhorn particles. The SEM analysis demonstrated that the particles produced by the ball mill have a roundish, red blood cell-like and irregular shape, similar to that observed in particles generated in vivo. In contrast, the particles produced by the Buchhorn method exhibited a flake-like and irregular morphology. The ball mill particles displayed a tendency towards agglomeration, which was also observed in particles generated in vivo. In conclusion, the ball mill method produces CoCrMo particles that closely resemble natural wear particles in terms of size and morphology. These particles provide a superior model for biological testing in comparison to those produced by the Buchhorn method. Furthermore, the ball mill method offers advantages in terms of reproducibility and scalability, making it a promising alternative for the generation of CoCrMo particles for orthopedic research.

Periprosthetic joint infections (PJI) are a common reason for orthopedic revision surgeries. It has been shown that the silver surface modification of a titanium alloy (Ti–6Al–4V) by PMEDM (powder mixed electrical discharge machining) exhibits an antibacterial effect on Staphylococcus spp. adhesion. Whether the thickness of the silver-modified surface influences the adhesion and proliferation of bacteria as well as the ossification processes and in-vivo antibacterial capacity has not been investigated before. Therefore, the aim of this work is to investigate the antibacterial effect as well as the in vitro ossification process depending on the thickness of PMEDM silver modified surfaces.

DAMAGE ANALYSIS OF RETRIEVED BIOLOX DELTA CERAMIC COMPONENTS FROM TOTAL HIP ARTHROPLASTIES

The detection and differentiation of BCP and CPP crystals in calcified tissue is an important factor in the context of research and potential future treatment of osteoarthritis and chondrocalcinosis. Current standard methods originate from clinical practice and often lack precision in the correct identification of the calcium crystal type. In this work, a step-by-step guide for the use of the high-resolution imaging methods of tissue sections, Raman spectroscopy and scanning electron microscopy (SEM) in combination with energy-dispersive X-ray spectroscopy (EDS), for calcium crystal identification is presented. Sample preparation including Von Kossa staining, measurement and measurement parameters, data processing and data analysis methods are discussed and described. Furthermore, the different methods are compared to show advantages and disadvantages. Overall, Raman spectroscopy is a reasonable method from an economic point of view and regarding the time/effort required for acquiring highly reliable data in calcium crystal identification. Potentially, semi-quantitative results can be obtained with little effort and without the destruction of the respective test sample. The analysis/penetration depth during the Raman measurements, which is not precisely defined, poses a potential problem for accuracy. SEM can also be used for this task but requires more time, advanced technical knowledge and a pre-treatment of the samples using, e.g., gold sputtering, which may distort further analysis on the specific specimen. Therefore, this technique yields additional value compared to Raman spectroscopy only with additional research questions needed to be answered in the same sample, such as analysis of the sample topography or analysis of other unknown particles/deposits using EDS. The methods described in this manuscript are helpful for retrospective analyses in the context of research, but can also be used for potential future treatment strategies to discriminate between osteoarthritis and chondrocalcinosis patients.