Biomedical subjects
Publications and source records attributed to J Ohnsorge.
When treating a septic hip-joint prosthesis with bone loss of the proximal femur secondary to osteomyelitis, we implanted a specially designed prosthesis to act as a local antibiotic and spacer between the acetabulum and femur until the infection abated. Arthroplasty could then be carried out with no trouble and there was no recurrence of infection.
The passive layer of a metal implant is responsible for its tolerance in a biological environment. A report is given on ESCA-investigations on the passive layer on Vitallium implants which consists largely of Cr-oxide and is only approx. 3-5 micrometer thick. This passive layer can easily be damaged with OP-instruments. The oxide layers rebuilt on exposure to air or on sterilization in boiling water were also investigated by ESCA. Oxide layers normally formed are very similar to the original passive layer. Accumulations of Co- and Mo-oxides are also observed, however. Some short implantation experiments show that the thin Cr-oxide layer is indeed effective as a passive layer. The analytical findings indicate that the formation or re-formation of the passive layer is due to a selective dissolution process. This accords with results obtained by the neutron activation analysis of the serum.
The uppermost monolayers of a metal implant are far more important for the corrosion resistance than the alloy itself. Using electron spectroscopy for chemical analysis (ESCA) technique these oxide layers on Vitallium specimens were investigated regarding thickness, elemental composition, and valence state of the elements. The oxide layers on metal implants are not very strong, as they can be easily damaged mechanically. According to environmental conditions, oxide layers of different elemental composition can be grown on the same specimen.
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The principals of the ESCA technique are described in details. Oxide layers on pure metals are investigated regarding composition and growth velocity. The valence state of a metal and the thickness of its oxid layer at the time of implantation into human body tissue are highly responsible for the corrosion resistance of this metal. Compared with Iron, Cobalt and Nickel and oxid layers of pure Titanium, Chromium and Molybdenum did not show further growth of thickness after several days in air. Immediately after removal of the passive layer only the stable and not the reactive oxids of the metal were restored.
Instrumental neutron activation analysis with Gamma-spectroscopy is a very sensitive method for testing trace elements. Specimens of contact tissue around 5 Blount's vitallium clamps were, after preparation at the Nuclear Research Institute Jülich irradiated with thermic neutrons and their element-specific gamma spectra were measured after 33 and 125 days. In contact tissue a significant rise in concentration of the alloy-specific elements cobalt and chromium was found. The unspecific elements silver, caesium, iron, rubidium, antimon, scandium and zink were either within or very close to the normal. The metallosis of contact tissue is due to corrosion of the surfaces of cobalt-chromium implants.
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