Figure 2.

Principle for the numerical computation of the bone remodelling after THA. The strain-adaptive bone remodelling in the periprosthetic femur was computed using the FEA. Figure 2 shows the principle of this procedure. The physiological load distribution in the intact femur according to a specific loading case was computed in one single cycle. For this, the strain energy per unit of mass S was calculated and serves as the reference data to compute the strain-adaptive bone remodelling. After THA, the load distribution in the periprosthetic femur, according to the same loading case as in the intact one, changes. In each computation step the stimulus ξ for the bone remodelling is calculated. Using the bone adaptation law, the new material properties of the bone structure in the femur after THA were determined for the next computation step. This is an iterative process, in which the simulation ends when convergence and thus the stationary state are reached. The computed elastic properties (ρ_end and E_end) of the bone in this final state are supposed to correspond to the periprosthetic femur's real long-term situation.