The study of mechanical behavior on the interface between calcar-defect femur and restorations by means of finite element analysis

The mechanical behaviors of calcar-defected femur and restorations under physiological load are the key factors that will greatly influence the success of femur calcar defect repairing, especially the stress distribution on the bone-restoration interface. 3D finite elements analysis (FEA) was used to analyze the mechanical characters on the interfaces between femoral calcar defects and bone cement or HA restorations. Under the load of two times of a human weight (1436.03 N) and with the increase of the defect dimension from 6 mm to 12 mm, the maximal stresses on the surface of restorations are from 7.06 MPa to 11.89 MPa for bone cement and 2.97–9 MPa for HA separately. In this condition, HA restoration will probably be broken on the bone-restoration interface when the defect diameter is beyond 8 mm. Furthermore, under the load of 1.5 times of a human weight, HA restoration would not be safe unless the defect dimension is smaller than 10 mm, because the maximal stress (4.62 MPa) on the restoration is only a little lower than compressive strength of HA, otherwise the bone fixation device should be applied to ensure the safety. It is relatively safe for all restorations under all the tested defect sizes when the load is just the weight of a human body.