Design of a dimpled femoral head in total hip replacements using elastohydrodynamic lubrication theory

In this paper, a three-dimensional computational and analytical elastohydrodynamic lubrication (EHL) analysis of a new dimpled design of an artificial hip joint is discussed. The shape, size and location of the dimple are known a priori. The method employed here differs from those found in literature, in that, unlike existing methods, which express the film thickness as a function of the eccentricities of the femoral head relative to the acetabular cup, the present method derives an expression for film thickness as a summation of film thickness from Reynolds equation, the elastic deflection, the geometry, the central film thickness and the contribution to the film thickness by the presence of the dimple. Therefore, in the present method, the film thickness and hence the pressure, has no dependence on eccentricities. The dimple, as sized and located in the present design, had negligible effect on the minimum film thickness, but did reduce the maximum pressure distribution between the femoral head and the acetabular cup. Optimization of the shape, size and location of the dimple is planned for the next phase of this work.