Patient-specific Biomechanical Modeling in Pre-Operative Surgical Planning

Larisa Goldmints, Carnegie Mellon University

Nowadays, computers are used in many areas traditionally dependent on human expertise, such as medicine. Computer-assisted orthopeadic surgery (CAOS) is the new area of computer application in medicine. It consists of three components: modeling, planning and execution. One of the most common sources of preoperative information in CAOS is medical imaging. Advances in medical imaging technology (computed tomography (CT), magnetic resonance imaging (MRI), etc.) and in computer-based image processing and modeling have made it possible to geometrically model and visualize anatomical structures in patients. These developments have given rise to the computer-based preoperative planners that are now appearing. The surgeon can interactively determine the operative procedure by manipulating computer-generated models of anatomical structures, surgical tools and/or implants. The computer can perform the simulations of the operative plan, giving the surgeon feedback on the proposed surgical procedure.

Existing preoperative planners do not relate the operation plan with the biomechanics of anatomical structures. Understanding the mechanics of orthopaedic surgery is particularly important, especially for cementless press-fitted implants. This work is the first attempt to incorporate patient-specific biomechanical simulation into a geometrical preoperative surgical planner. This can provide the surgeon with qualitatively new tools for computer-assisted surgery.

The complexity of anatomical structures requires the use of numerical methods, such as the FE method, to perform biomechanical simulations. Existing mesh generation techniques cannot automatically produce FE meshes of three-dimensional models of arbitrary geometry. Moreover, geometric modeling of patient-specific anatomical structure, which underlies existing preoperative planners, is still under development. A new method to automatically obtain three-dimensional FE models from CT scan data will be developed. This method utilizes mapping techniques, commonly applied for registration of MRI of the human brain. The method provides segmentation as a byproduct, which can be compared to the geometric planner's segmentation as a validation step. In the future, surface models obtained from FE models can also be used within geometrical preoperative planners. FE simulation of the acetabular component of Total Hip Replacement (THR) will be performed using patient-specific three-dimensional pelvic model of anatomical geometry.

Although this research is motivated by a specific problem of biomechanical analysis of the acetabular component of THR, the methods to be developed within this framework are general and can be applied to other biomechanical and medical imaging problems.

Abstract Author(s): Larisa Goldmints