Development and Validity of Tissue Biomechanics Modeling for Virtual Robot Assisted Orthopedic Surgery System

Information with respect to the internal stresses/strains in the human leg during bone-setting is helpful to control the medical robots in HIT-robot assisted orthopedic surgery system (HIT-RAOS). While techniques to measure external pressure are well established, direct measurement of the internal stresses/strains is difficult. A three-dimensional (3D) finite element model of the human leg is developed using the actual geometry of the leg skeleton and soft tissues, which were obtained from 3D reconstruction of CT images. The major tendons are simulated using tension-only truss elements by connecting the corresponding attachment points on the bone surfaces. The bony structures are defined as linearly elastic, while the soft tissue and muscles are assumed to be hyper elastic. The bony and tendons structures are embedded in a volume of soft tissues. To validate this model, the same cadaver is utilized in experiment, during reposition procedure, the force needed to separate the two broken bones and corresponding the distance are recorded. Then, another set of data is acquired from the finite element analysis. After comparison, the finite element model is proved to be acceptable. This simulation model is used in virtual HIT-robot assisted orthopedic surgery system.