title: Nonlinear quasi-static finite element simulations predict in vitro strength of human proximal femora assessed in a dynamic sideways fall setup.
abstract: Osteoporotic proximal femur fractures are caused by low energy trauma, typically when falling on the hip from standing height. Finite element simulations, widely used to predict the fracture load of femora in fall, usually include neither mass-related inertial effects, nor the viscous part of bone׳s material behavior. The aim of this study was to elucidate if quasi-static non-linear homogenized finite element analyses can predict in vitro mechanical properties of proximal femora assessed in dynamic drop tower experiments. The case-specific numerical models of 13 femora predicted the strength (R(2)=0.84, SEE=540N, 16.2%), stiffness (R(2)=0.82, SEE=233N/mm, 18.0%) and fracture energy (R(2)=0.72, SEE=3.85J, 39.6%); and provided fair qualitative matches with the fracture patterns. The influence of material anisotropy was negligible for all predictions. These results suggest that quasi-static homogenized finite element analysis may be used to predict mechanical properties of proximal femora in the dynamic sideways fall situation.
authors.affiliation: AO Research Institute Davos, Switzerland. Electronic address: peter.varga@aofoundation.org.
authors.forename: Peter
authors.initials: P
authors.lastname: Varga
authors.affiliation: Institute of Surgical Technology and Biomechanics, University of Bern, Switzerland.
authors.forename: Jakob
authors.initials: J
authors.lastname: Schwiedrzik
authors.affiliation: Institute of Surgical Technology and Biomechanics, University of Bern, Switzerland.
authors.forename: Philippe K
authors.initials: PK
authors.lastname: Zysset
authors.affiliation: AO Research Institute Davos, Switzerland.
authors.forename: Ladina
authors.initials: L
authors.lastname: Fliri-Hofmann
authors.affiliation: AO Research Institute Davos, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Widmer
authors.affiliation: AO Research Institute Davos, Switzerland.
authors.forename: Boyko
authors.initials: B
authors.lastname: Gueorguiev
authors.affiliation: Department of Trauma Surgery, University Hospital Innsbruck, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Blauth
authors.affiliation: AO Research Institute Davos, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Windolf
mesh_terms: D000058:Accidental Falls; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur / Q000293:injuries; D020342:Finite Element Analysis; D050723:Fractures, Bone; D006801:Humans; D008297:Male; D008422:Materials Testing; D055595:Mechanical Phenomena; D017711:Nonlinear Dynamics
keywords: Drop tower test; Finite element analysis; Fracture pattern; Proximal femur fracture; Quasi-static model