One of the major problems in hip replacement surgery is the hipreplacement loosening. Hip replacement loosening occurs over time after thesurgery and it is related to the discretization between the bone cement andprosthesis. The underlying factors of this situation are the stress occurring inthe bone cement and the shape of the prosthesis. In this study, cortical andtrabecular layers of the femur, bone cement and prosthesis were modeled. Themodels of bone cement and prosthesis were constructed parametrically andtwo different sinusoidal formed prostheses were developed unlike the formerprostheses shapes. Analyses were conducted for these two different sinusoidalforms by using finite element method and optimization was conducted to obtainthe appropriate prosthesis stem shape and bone cement thickness by usingparametric modeling in finite element analyses. For finite element analyses andoptimization, Ansys Workbench software was used and analyses wereconducted for 316LS stainless steel material. Finally, the optimum prosthesisstem shape and bone cement thickness was determined by using the results ofthe analyses in the first stage.One of the major problems in hip replacement surgery is the hip replacement loosening. Hip replacement loosening occurs over time after the surgery and it is related to the discretization between the bone cement and prosthesis. The underlying factors of this situation are the stress occurring in the bone cement and the shape of the prosthesis. In this study, cortical and trabecular layers of the femur, bone cement and prosthesis were modeled. The models of bone cement and prosthesis were constructed parametrically and two different sinusoidal formed prostheses were developed unlike the former prostheses shapes. Analyses were conducted for these two different sinusoidal forms by using finite element method and optimization was conducted to obtain the appropriate prosthesis stem shape and bone cement thickness by using parametric modeling in finite element analyses. For finite element analyses and optimization, Ansys Workbench software was used and analyses were conducted for 316LS stainless steel material. Finally, the optimum prosthesis stem shape and bone cement thickness was determined by using the results of the analyses in the first stage