Intact and implanted femur behaviour during walking and jogging

The static position of single leg stance is a generally accepted worst case scenario for hip joint loading. However, it is essential in particular for investigations including temporal effects such as studies on fracture healing, fatigue, micromotion and remodeling to examine the dynamic loading situation not only at a single moment in time, but during the complete range of motion. In this study, a three-dimensional dynamic finite element model of the human femur during the gait cycle is developed. A temporally varying hip joint reaction force distribution during walking and jogging is employed and a temporally varying abductor muscles force is included while the distal end of the femur is constrained in translation only. The distribution of the displacements and stresses throughout the femur during different instants of the gait cycle is obtained in both loading conditions and compared. Also, an intramedullary prosthesis is nailed in the previous model and the femur-prosthesis is subjected to a similar type of loading. The results can be used to visualise the mechanical environment in the intact femur during dynamic loading and compare it to that after total hip arthroplasty. Such knowledge is vital for surgical procedures, healing processes as well as therapeutic regimes.