Finite element analysis of a three-dimensional model of a proximal femur-cemented femoral THJR component construct: influence of assigned interface conditions on strain energy density.

A finite element analysis of the stresses in a construct, comprising a three-dimensional model of the proximal human femur in which the stem of a total hip joint replacement was cemented, was performed. The one-legged standing condition was used, with all applied forces on the proximal femur being considered. These forces were the resultant hip joint reaction force and the forces due to the activation of the abductor, ilio-psoas, and ilio-tibialis muscles. The cortical and cancellous bones were assigned anisotropic elastic properties. It was found that the mean value of the strain energy density at each of the regions considered was considerably higher when debonding was considered at both the cancellous bone-acrylic bone cement and bone cement-stem interfaces (represented using surface-to-surface Coulomb friction, coefficient of friction = 0.22) compared to when perfect bonding conditions were taken to exist at these interfaces. The significance of this finding, together with the study limitations, is discussed.