Abstract
Acetabular prosthesis loosening is associated with structural characteristics of the implant-bone system and the operative procedure. In order to improve the service life of the cup, it is important to develop the material, design, fixation mechanism, etc. and to assess the mechanical behavior around the cup. In this study, stress condition around the artificial acetabular cup before and after the worn is investigated by three-dimensional finite element method. The FEM model was constructed on the basis of the CT image around the cup and profile measurements of the cup worn in vivo for approximately 15 years. The results obtained are as follows. (1) In the cup before the worn, the load transmitted from femoral head to cup is mainly distributed within the cup, and the influence on bone cement and cancellous bone is small. (2) In the worn cup, the load is not sufficiently distributed within the cup, and as a result, the compression stress is caused locally in the worn area of the cup and the tensile stress in the circumference increases. (3) The tensile stress inclination increases in the boundary of bone cement and cancellous bone, when the thickness of bone cement is small.
