Analysis of Force Flow in Natural and Artificial Hip Joints Using the Finite-Element Method

摘要

Detailed knowledge of the force flow (in magnitude and direction) is essential for the design and comparative evaluation of artificial hip joints. In this paper, the authors present a finite element analysis based on the use of a tetrahedron as the basic volume element. The calculation model has approximately 3000 degrees of freedom. Comparative analyses are carried out for a natural femur, for a number of conventional endoprostheses with different fixations, as well as for a new endoprosthesis design. These analysis have yielded surprising results. In particular, it is found that the medial radial stresses are strongly dependent on the fixation conditions (i.e. support of the endoprosthesis pin, etc.) and the dissimilarities between these bone stresses and those in the natural (physiological) case often cause bone failures. The force-flow results for an implanted endoprosthesis of the new type indicate that this type of appliance has definite advantages, in closely similating the natural stress distribution.