Finite Element Analysis of the Elbow After Joint Replacement

Summary

The stresses in bone, implant and bone-cement for three different elbow endoprostheses have been calculated using the finite element method. The geometry and material properties of all components were transferred to the three-dimensional models with high accurracy. Strain gauges were used to check experimentally the analytical results. Good agreement could be achieved. For an implant with short fixation parts (model OHH) great stress protection in the surrounding bone is predicted. The stresses at the ulna surface are more reduced due to an implant than the stresses on the humerus surface.

In another model the influence of interface conditions (rigid, loose) on the stresses around long stem implants has been studied. Allowing separation in the interface the stresses at the distal and proximal ends of the interface change significantly compared to the rigid bonded case.

For an isoelastic endoprosthesis the highest stresses and relative motion occur at the proximal end whereas for a metal implant the highest values are calculated at the distal end of the stem. The maximal value for relative motion for an isoelastic implant is predicted to be twice as high as the maximal value for an implant made of Co-Cr-Mo alloy.

This work was supported by grants from the German Ministery for Research and Technology (NT 01 VG 061) and from the Deutsche Forschungsgemeinschaft.