An investigation on the effect of stem size and type of prosthesis fixation on stress distribution of the femur using finite element method

The effect of stem size and the type of fixation of the prosthesis on the stress distribution in the femoral part of the knee joint is studied here. In this investigation a two dimensional model of a section in the external condyle of distal femur is considered for stress analysis. This model is solved by using the finite element method and by the aid of SAP90 software. The stress analysis and shape deformation are done in 8 different models and each model under 4 different flexion conditions: namely 0, 30, 60 and 90 degrees. By assuming that the constituting elements are made of isotropic material the following results are obtained. A short length prosthesis causes an increase in the stress level of the cortical bone of in the posterior part of the shaft. A prosthesis with a medium sized stem, produces a stress distribution similar to the no prosthesis case. The application of a long size stem decreases the stress level in the cortical bone of the posterior part of the shaft. For a prosthesis with no stem and no cement an increase in the stress level in the cortical bone of the posterior part of the shaft is seen. Furthermore, implanting the prosthesis with cement causes a greater reduction in the stress level