title: Trabecular deformations during screw pull-out: a micro-CT study of lapine bone.
abstract: The mechanical fixation of endosseous implants, such as screws, in trabecular bone is challenging because of the complex porous microstructure. Development of new screw designs to improve fracture fixation, especially in high-porosity osteoporotic bone, requires a profound understanding of how the structural system implant/trabeculae interacts when it is subjected to mechanical load. In this study, pull-out tests of screw implants were performed. Screws were first inserted into the trabecular bone of rabbit femurs and then pulled out from the bone inside a computational tomography scanner. The tests were interrupted at certain load steps to acquire 3D images. The images were then analysed with a digital volume correlation technique to estimate deformation and strain fields inside the bone during the tests. The results indicate that the highest shear strains are concentrated between the inner and outer thread diameter, whereas compressive strains are found at larger distances from the screw. Tensile strains were somewhat smaller. Strain concentrations and the location of trabecular failures provide experimental information that could be used in the development of new screw designs and/or to validate numerical simulations.
authors.affiliation: Materials in Medicine Group, Division of Applied Materials Science, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden. thomas.joffre@angstrom.uu.se.|Applied Mechanics, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden. thomas.joffre@angstrom.uu.se.
authors.forename: Thomas
authors.identifier: 0000-0002-1524-2497
authors.initials: T
authors.lastname: Joffre
authors.affiliation: Applied Mechanics, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Isaksson
authors.affiliation: Materials in Medicine Group, Division of Applied Materials Science, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden.
authors.forename: Philip
authors.initials: P
authors.lastname: Procter
authors.affiliation: Materials in Medicine Group, Division of Applied Materials Science, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Persson
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001863:Bone Screws / Q000592:standards; D000071556:Cancellous Bone / Q000601:surgery; D005592:Fracture Fixation / Q000295:instrumentation; D021621:Imaging, Three-Dimensional; D023421:Models, Animal; D011817:Rabbits; D055114:X-Ray Microtomography
keywords: Digital volume correlation; Implants; Micro-CT; Pull-out test; Screws; Trabecular bone