title: Development of a balanced experimental-computational approach to understanding the mechanics of proximal femur fractures.
abstract: The majority of people who sustain hip fractures after a fall to the side would not have been identified using current screening techniques such as areal bone mineral density. Identifying them, however, is essential so that appropriate pharmacological or lifestyle interventions can be implemented. A protocol, demonstrated on a single specimen, is introduced, comprising the following components; in vitro biofidelic drop tower testing of a proximal femur; high-speed image analysis through digital image correlation; detailed accounting of the energy present during the drop tower test; organ level finite element simulations of the drop tower test; micro level finite element simulations of critical volumes of interest in the trabecular bone. Fracture in the femoral specimen initiated in the superior part of the neck. Measured fracture load was 3760N, compared to 4871N predicted based on the finite element analysis. Digital image correlation showed compressive surface strains as high as 7.1% prior to fracture. Voxel level results were consistent with high-speed video data and helped identify hidden local structural weaknesses. We found using a drop tower test protocol that a femoral neck fracture can be created with a fall velocity and energy representative of a sideways fall from standing. Additionally, we found that the nested explicit finite element method used allowed us to identify local structural weaknesses associated with femur fracture initiation.
authors.affiliation: Institute for Biomechanics, ETH-Zürich, Switzerland. Electronic address: bhelgason@ethz.ch.
authors.forename: B
authors.initials: B
authors.lastname: Helgason
authors.affiliation: Orthopaedic and Injury Biomechanics Group, University of British Columbia, Vancouver, Canada; Centre for Hip Health and Mobility, University of British Columbia, Vancouver, Canada; Department of Mechanical Engineering, University of British Columbia, Vancouver, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Gilchrist
authors.affiliation: Institute for Biomechanics, ETH-Zürich, Switzerland; Orthopaedic and Injury Biomechanics Group, University of British Columbia, Vancouver, Canada; Centre for Hip Health and Mobility, University of British Columbia, Vancouver, Canada; Department of Mechanical Engineering, University of British Columbia, Vancouver, Canada.
authors.forename: O
authors.initials: O
authors.lastname: Ariza
authors.affiliation: Orthopaedic and Injury Biomechanics Group, University of British Columbia, Vancouver, Canada; Department of Mechanical Engineering, University of British Columbia, Vancouver, Canada; Department of Orthopedics, University of British Columbia, Vancouver, Canada.
authors.forename: J D
authors.initials: JD
authors.lastname: Chak
authors.affiliation: Institute for Surgical Technology and Biomechanics, University of Bern, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Zheng
authors.affiliation: Institute for Biomechanics, ETH-Zürich, Switzerland.
authors.forename: R P
authors.initials: RP
authors.lastname: Widmer
authors.affiliation: Institute for Biomechanics, ETH-Zürich, Switzerland.
authors.forename: S J
authors.initials: SJ
authors.lastname: Ferguson
authors.affiliation: Centre for Hip Health and Mobility, University of British Columbia, Vancouver, Canada; Department of Orthopedics, University of British Columbia, Vancouver, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Guy
authors.affiliation: Orthopaedic and Injury Biomechanics Group, University of British Columbia, Vancouver, Canada; Centre for Hip Health and Mobility, University of British Columbia, Vancouver, Canada; Department of Mechanical Engineering, University of British Columbia, Vancouver, Canada; Department of Orthopedics, University of British Columbia, Vancouver, Canada.
authors.forename: P A
authors.initials: PA
authors.lastname: Cripton
mesh_terms: D000058:Accidental Falls; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D005260:Female; D005264:Femoral Fractures / Q000503:physiopathology*; D020342:Finite Element Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008422:Materials Testing; D008954:Models, Biological; D014741:Video Recording
keywords: Digital image correlation; Drop tower testing; Femur; Finite element analysis; Osteoporosis