Influence of three variables on the stresses in a three-dimensional model of a proximal tibia-total knee implant construct.

A finite element analysis of the stresses in a three-dimensional model of the proximal human tibia containing the tibial components (insert, tray, and stem) of a cemented total knee joint replacement was conducted. 12 cases of this model, covering three variables (composition of applied loading, interface conditions, and assignment of elastic properties to the cortical and cancellous bones) were analyzed. It was found that the stresses in various parts of the model were markedly lower when (a) the applied load comprised a compressive joint reaction force (F), of 2 kN, only (quadriceps inactive) versus F+ a patellar ligament force of 1.46 kN (P), representing the situation when the quadriceps are active; and (b) the interfaces were considered fully bonded compared to when they represented as having surface-to-surface Coulomb frictional contact (coefficient of friction = 0.2). However, the nature of the elastic properties that were assigned to the bones (isotropic versus anisotropic) had only a marginal influence on the stresses.