TRIBOLOGY OF ELLIPTICAL HIP JOINT PROSTHESIS
Journal Title: Tribologia - Year 2014, Vol 254, Issue 2
Abstract
The presented paper shows and gives the reasons for the contemporary failures occurring in alloplastic (human hip joint prosthesis) performances such as the locally boosted friction forces and stresses and breaks of the prosthesis pin. This paper was motivated by the application of a spherical rather than elliptical head of a prosthesis that is not sufficiently adapted to the elliptical geometry of the natural acetabulum surfaces. The negative effects are enlarged by the stochastic standard effects occurring during the prosthesis exploitation. Numerous contemporary studies and experimental measurements regarding the human hip joints indicate that the femoral head is in fact naturally elliptical. Therefore, the elliptical head in hip prosthesis must be better adapted to the elliptical surface geometry of the natural acetabulum in comparison with the spherical head. Half prostheses of hip joints are applied when joint acetabulum cartilage is well maintained. In the half prosthesis, the head is welded to the spindle or seated to the pin. When acetabulum cartilage is worn (used), a complete prosthesis is implanted. The elliptical femoral prosthesis was designed to solve the problem of the relationship between the femoral prosthesis head and the anatomical acetabulum and to minimize the various incidence of wear protrusion and pain effects. Performed clinical tests indicate that elliptical prosthesis heads have the most advanced technological shapes, because they are based on the anatomy and biomechanics features of the natural human hip joint. The biomechanics of an elliptical head femoral prosthesis can be taken as the appropriate shape in respect to the treatment of medical fractures of the neck of the femur. Taking into account the hydrodynamic theory of the lubrication of cooperating surfaces, we must find pressure distributions, friction forces, friction coefficients, and wear. To prepare these calculations, we first determine and calculate the fields of the regions of lubrication on the internal surface lying on the elliptical femoral prosthesis (i.e. acetabulum) and on the external elliptical surface of the artificial bone or femoral head.
Authors and Affiliations
Krzysztof WIERZCHOLSKI
Keywords
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