Biomechanical Role of Bone Anisotropy Estimated on Clinical CT Scans by Image Registration
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Image-based modeling is a popular approach to perform patient-specific biomechanical simulations. Accurate modeling is critical for orthopedic application to evaluate implant design and surgical planning. It has been shown that bone strength can be estimated from the bone mineral density (BMD) and trabecular bone architecture. However, these findings cannot be directly and fully transferred to patient-specific modeling since only BMD can be derived from clinical CT. Therefore, the objective of this study was to propose a method to predict the trabecular bone structure using a µCT atlas and an image registration technique. The approach has been evaluated on femurs and patellae under physiological loading. The displacement and ultimate force for femurs loaded in stance position were predicted with an error of 2.5% and 3.7%, respectively, while predictions obtained with an isotropic material resulted in errors of 7.3% and 6.9%. Similar results were obtained for the patella, where the strain predicted using the registration approach resulted in an improved mean squared error compared to the isotropic model. We conclude that the registration of anisotropic information from of a single template bone enables more accurate patient-specific simulations from clinical image datasets than isotropic model.
KeywordsTrabecular bone Femur Patella Anisotropy Finite element analysis (FEA)
The authors would like to thank Dr. Enrico Dall’Ara for preparing, scanning and sharing the femoral data, Dr. Jakob Schwiedrzik for providing the UMAT implementation of the mechanical model, Prof. Dieter Pahr for giving us access to the Medtool software and Dr. Ghislain Maquer and Dr. Hadi Seyed Hosseini for their assistance on the preparation of the FE models.
The authors have no commercial, proprietary, or financial interest in any products or companies described in this article.
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