This paper describes how to create interactions between the virtual world and the medical environment to solve one of the problems frequently encountered during the design phases of operations, highlighting the importance of this project in the realm of Applied R&D + i for high-detail, patient-specific medical operations. In particular, rotations and translations required to solve valgus and varus problems of the tibia and femur are analyzed. Currently, prostheses are produced using non-specific software that requires the presence of an external operator. A virtual reality (VR) application to improve the interaction between the software and the surgeon, thus simplifying the prosthesis design process, is presented. The method proposed in this paper applies mechanical design to the medical field, starting from the principles of Industry 4.0 for human–machine interaction. Virtual Reality implements mechanical concepts such as the hinge and its function in virtual environments like Unity. This approach allowed us to limit the movement of an object in space to rotations around an axis defined by the end user, making these rotations ‘parametric’, i.e. traceable to finite mathematical values. It was demonstrated that the design of wedge-shaped prostheses for realigning the tibia and femur during surgery has been thus simplified.