[Abrasion reducing polyethylene ceramic-metal compound hip prosthesis head]. / PE-verschleissmindernde Keramik-Metallverbund-Hüftgelenkkugeln.

There are two specific problems in using metallic or ceramic heads for hip prostheses: (1) the amount of polyethylene abrasions in the cup caused by the heads (especially a metal head). (2) the polyethylene abrasions caused by Al2O3 ceramic heads is far less than metal heads, but its ability to adapt geometrically is limited due to its being less strong. The abrasions appear because of geometric differences in the prosthetic joint, local problems in the surface architecture and physical/chemical interactions between the different materials. In this study we compare the new "Titan-Niob Ceramic Multilayer Sandwich Head" (built three layers of microsegregation phases and three in-between layers of ultrathin metal, 8-10 microns thick, and a surface with integrated grease holes) with the common CoCrMo heads and Al2O3 ceramic heads. Testing 2,000,000 cycles in a bodylike liquid under permanent loads of 90 kPa, periodically increasing up to 250 kPa, simulating normal stress situations (i.e., walking), the "Titan-Niob Ceramic Multilayer Sandwich Head" showed major advantages over the metal heads and also over the ceramic heads even though the ceramic head has been accepted so far to have the best friction coefficient. Furthermore, there has been no problem in surface fracture with the "Titan-Niob Ceramic Multilayer Sandwich Head".

[A comparative study of the characteristics of femoral hip prosthesis heads--study and results ceramic-coated hip joint heads of titanium]. / Eine Vergleichsstudie zur Oberschenkelbeschaffenheit von Hüftprothesenköpfen--Untersuchung und Ergebnisse cerid-beschichteter Hüftgelenkskugeln aus Titan.

Today, only hard/soft cup and femoral head combinations are employed for hip joint prostheses. Highly polished ceramic is a material with very good tribological properties for femoral heads, being highly resistant to mechanical wear and tear, and highly resistant to chemical reactions in the biological environment. The advantage of metal heads, in contrast, undoubtedly lies in their resistance to breakage and the ease with which their geometry can be modified with respect, for example, to antirotation angle and neck length. The ideal material for femoral heads is a combination of the two materials. The new multi-layer combination of titanium-niobium oxide/nitride ceramic coating applied to a prehardened titanium head combines the positive material properties in an ideal manner. Femoral heads made of CoCrMo, oxide-hardened titanium, aluminium oxide or multilayer titanium-niobium ceramic were compared by means of friction an wear and tear tests. The TiNb-ceramic-metal heads showed similar abrasion at the surface as the ceramic heads. At the high loads of more than 400 kp, which may also be reached under physiological conditions, the specially coated titanium-ceramic heads proved to be superior in terms of resistance to fracture and tribological properties.