title: Rib fractures under anterior-posterior dynamic loads: experimental and finite-element study.
abstract: The purpose of this study was to investigate whether using a finite-element (FE) mesh composed entirely of hexahedral elements to model cortical and trabecular bone (all-hex model) would provide more accurate simulations than those with variable thickness shell elements for cortical bone and hexahedral elements for trabecular bone (hex-shell model) in the modeling human ribs. First, quasi-static non-injurious and dynamic injurious experiments were performed using the second, fourth, and tenth human thoracic ribs to record the structural behavior and fracture tolerance of individual ribs under anterior-posterior bending loads. Then, all-hex and hex-shell FE models for the three ribs were developed using an octree-based and multi-block hex meshing approach, respectively. Material properties of cortical bone were optimized using dynamic experimental data and the hex-shell model of the fourth rib and trabecular bone properties were taken from the literature. Overall, the reaction force-displacement relationship predicted by both all-hex and hex-shell models with nodes in the offset middle-cortical surfaces compared well with those measured experimentally for all the three ribs. With the exception of fracture locations, the predictions from all-hex and offset hex-shell models of the second and fourth ribs agreed better with experimental data than those from the tenth rib models in terms of reaction force at fracture (difference <15.4%), ultimate failure displacement and time (difference <7.3%), and cortical bone strains. The hex-shell models with shell nodes in outer cortical surfaces increased static reaction forces up to 16.6%, compared to offset hex-shell models. These results indicated that both all-hex and hex-shell modeling strategies were applicable for simulating rib responses and bone fractures for the loading conditions considered, but coarse hex-shell models with constant or variable shell thickness were more computationally efficient and therefore preferred.
authors.affiliation: Center for Applied Biomechanics, University of Virginia, Charlottesville, VA, USA. zl4c@virginia.edu
authors.forename: Zuoping
authors.initials: Z
authors.lastname: Li
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Kindig
authors.forename: Jason R
authors.initials: JR
authors.lastname: Kerrigan
authors.forename: Costin D
authors.initials: CD
authors.lastname: Untaroiu
authors.forename: Damien
authors.initials: D
authors.lastname: Subit
authors.forename: Jeff R
authors.initials: JR
authors.lastname: Crandall
authors.forename: Richard W
authors.initials: RW
authors.lastname: Kent
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002102:Cadaver; D003198:Computer Simulation; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D008954:Models, Biological; D012253:Rib Fractures / Q000473:pathology / Q000503:physiopathology*; D013314:Stress, Mechanical