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Forschungsdatenbank PMU-SQQUID

Evaluation of Osteosynthesis Options and Fracture Healing Progress from Computed Tomography Based Finite Element Analysis
Koerber, J; Eberle, S; Augat, P
IFMBE PROC. 2010; 25: 367-369.


Augat Peter


The bone healing process is primarily determined by the mechanical environment provided by osteosynthesis and the bone itself. The purpose of this study was to develop and validate patient-specific finite element analysis (FEA) generated from computed tomography (CT) data for the evaluation of fracture stability. These models have two primary purposes: To evaluate initial fracture stability with various osteosynthesis options and to assess changes in the stability during the fracture healing process. In order to create patient-specific finite element models for various osteosynthesis options, trabecular bone and cortical bone were segmented according to their CT Hounsfield Units (HU), the 3D geometries of these tissues were generated and potential implants were inserted into the model. Custom-written software was used to assign local bone mineral density (BMD) to elements in the model, from which BMD-based material laws allow the stiffness of the bone to be predicted. To validate the estimated mechanical properties, eight human femora were scanned and afterwards were loaded to simulate the actual loads occurring in the femur. The overall stiffness was measured with a materials testing system and local displacements were measured by a 3D video measurement system for intact bone and for A3.1 and A3.3 fractures. The overall stiffness and local displacements were calcula-ted with FEA and compared to the mechanical test results. It was found that the accuracy of these models was highly sensitive to the BMD-based material law used. Estimates of overall stiffness and deformation at specific points within 15% were possible. Finite element models of fracture callus are currently being validated with fractured ovine tibias at 6 weeks healing time. In the future, patient-specific FEA from CT scans may be a useful tool to evaluate osteosynthesis options for a particular fracture scenario and for evaluating the healing progress of a fracture.