In Silico Analysis of Bone Tension During Fixation of the Medial Malleolus Fracture After Ankle Joint Endoprosthesis.

ABSTRACT

Total ankle arthroplasty (TAR) is a procedure alternative to arthrodesis which enables the biomechanical stabilization of the ankle joint. The procedure is associated with a high risk of complications, including fractures of the medial malleolus. In this study, the finite element method (FEM), based on CT examinations, was used to model the ankle fracture fixation after TAR. Three types of fracture stabilization were considered screw, Blount staple, and both screw and Blount staple. In the in silico model, the maximum stress tension was found at prosthetic junctions with the base, cone, and talar components of the tibial prosthesis. When the fracture was stabilized with the Blount staple, tension along the cone of the tibial component was about 12% of the maximum tension. Stabilizations with the screw alone or Blount staple combined with a screw on the medial side of the cone induced tension in the immediate vicinity twice as high. In the area of the medial malleolus, the tension was alike for both types of stabilization. The tension was lowest when using the Blount staple alone. We conclude that, contrary to the hitherto clinical routine of using screws, fracture fixation using the Blount staple leads to the lowest bone tension around the fixation of the medial malleolus fracture after ankle joint endoprosthesis.