title: A novel methodology for generating 3D finite element models of the hip from 2D radiographs.
abstract: Finite element (FE) modelling has been proposed as a tool for estimating fracture risk and patient-specific FE models are commonly based on computed tomography (CT). Here, we present a novel method to automatically create personalised 3D models from standard 2D hip radiographs. A set of geometrical parameters of the femur were determined from seven a-p hip radiographs and compared to the 3D femoral shape obtained from CT as training material; the error in reconstructing the 3D model from the 2D radiographs was assessed. Using the geometry parameters as the input, the 3D shape of another 21 femora was built and meshed, separating a cortical and trabecular compartment. The material properties were derived from the homogeneity index assessed by texture analysis of the radiographs, with focus on the principal tensile and compressive trabecular systems. The ability of these FE models to predict failure load as determined by experimental biomechanical testing was evaluated and compared to the predictive ability of DXA. The average reconstruction error of the 3D models was 1.77 mm (±1.17 mm), with the error being smallest in the femoral head and neck, and greatest in the trochanter. The correlation of the FE predicted failure load with the experimental failure load was r(2)=64% for the reconstruction FE model, which was significantly better (p<0.05) than that for DXA (r(2)=24%). This novel method for automatically constructing a patient-specific 3D finite element model from standard 2D radiographs shows encouraging results in estimating patient-specific failure loads.
authors.affiliation: Department of Medical Technology, University of Oulu, Oulu 90014, Finland.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Thevenot
authors.affiliation: Department of Medical Technology, University of Oulu, Oulu 90014, Finland.
authors.forename: Janne
authors.initials: J
authors.lastname: Koivumäki
authors.affiliation: Institute of Anatomy, Ludwig-Maximilians-University, Munich, Germany; Department of Trauma Surgery and Sports Medicine, Medical University, Innsbruck, Austria.
authors.forename: Volker
authors.initials: V
authors.lastname: Kuhn
authors.affiliation: Institute of Anatomy, Ludwig-Maximilians-University, Munich, Germany; Institute of Anatomy and Musculoskeletal Research, Paracelsus Medical University, Salzburg, Austria.
authors.forename: Felix
authors.initials: F
authors.lastname: Eckstein
authors.affiliation: Department of Medical Technology, University of Oulu, Oulu 90014, Finland; Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland. Electronic address: timo.jamsa@oulu.fi.
authors.forename: Timo
authors.initials: T
authors.lastname: Jämsä
mesh_terms: D055119:Elastic Modulus / Q000528:radiation effects; D005260:Female; D005270:Femur Head / Q000000981:diagnostic imaging*; D020342:Finite Element Analysis; D050723:Fractures, Bone; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed; D014129:Trabecular Meshwork / Q000000981:diagnostic imaging
keywords: Biomechanics; Finite element method; Hip fracture; Radiography; Structure analysis