Complication rates of hip fractures after proximal femoral nail are not rare. In such fractures, treatment invariably comprises the extraction of proximal femoral nail and the introduction of a different hip prosthesis. To solve this problem, we aimed to develop a new implant, the modular nail prosthesis, which combines an intramedullary nail with a hip prosthesis. The aim of this study was to determine the effect of stress load distribution on the stem using finite element analysis under laboratory conditions. For this, the shortest stem of 175mm was chosen. In addition, six proximal femoral nail-hip prosthesis combinations were produced and tested with a biomechanical test device and passed 2300-N load bearing. According to the test results, our newly developed modular nail prosthesis can be converted to hip prosthesis securely.