This study focused on the design of specific prostheses in the case of patients affected by Chordoma of the lumbar 4, lumbar 5, sacrum, and coccyx. A chordoma is a group of malignant and rare cancers, commonly found in the spine or skull bones. As a treatment method, if cancer has not spread beyond the bone, the infected bone's removal procedure is replaced with an artificial bone (prosthesis). The design method is carried out using a CT Scan of patient data, which is processed into a 3D model with Materialise Mimics software, 3D model engineering is done using Solidworks software and finite element analysis with ANSYS. The design process is carried out with several kinds of design variations, including the bone-implant model with a solid and shell model which is divided into several components, the use of iliac screw lateral connector, modification of iliac screw locking head, and modification of iliac screw locking head with cross connector. From the results of the calculation analysis and simulation, the best concept chosen based on the lowest dominant Peak von Mises Stress value in the iliac screw section is designs using the Iliac Screw Locking Head with Shell Model Lattice Structure.