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.Electronic supplementary materialThe online version of this article (doi:10.1007/s10237-017-0891-9) contains supplementary material, which is available to authorized users.

Experimental Evaluation of Screw Pullout Force and Adjacent Bone Damage According to Pedicle Screw Design Parameters in Normal and Osteoporotic Bones

“…When stresses that exceeded the yield stress of the artificial bone were applied on it, deformation occurred in the contact area between the artificial bone and screw. When the maximum stress was exceeded, the artificial bone was broken at the contact lower part and upper part of the screw, and the screw was loosened and debonded [20]. Finally, when the conical angle increased, deformation and fracture of the artificial bone contacted screw rapidly occurred.…”

Bone Damage Evolution Around Integrated Metal Screws Using X-Ray Tomography — in situ Pullout and Digital Volume Correlation

“…This is consistent with observations made directly from the tomographic images and can be explained by the rather smooth screw threads. To our knowledge, only one other study experimentally investigated screw pullout using in situ loading ( Joffre et al, 2017 ). They observed strains initiating in close proximity of the implant (<500 μm), and decreasing radially inside the bone (up to 2 mm), which they attributed to bending of the trabeculae.…”

“…Concurrent mechanical testing and imaging approaches have recently become widely accepted to track the load response of bone tissue and to study the evolution of damage and local failure ( Dall’Ara et al, 2014 ; Gillard et al, 2014 ; Palanca et al, 2015 ; Jackman et al, 2016 ; Chen et al, 2017 ; Costa et al, 2017 ; Le Cann et al, 2017 ; Martelli and Perilli, 2018 ; Oliviero et al, 2018 ; Peña Fernández et al, 2018 ; Knowles et al, 2019 ). However, only sparse studies have applied the method to the bone-implant interface ( Du et al, 2015 ; Sukjamsri et al, 2015 ; Joffre et al, 2017 ; Le Cann et al, 2017 ; Rapagna et al, 2019 ).…”

Heterogeneous Strain Distribution in the Subchondral Bone of Human Osteoarthritic Femoral Heads, Measured with Digital Volume Correlation

“…This technique has been employed to evaluate full-field internal deformations in bone structures at the organ and tissue levels [ 17 , 18 ]. The DVC approach has also been used to study the effect of biomaterials and implants on the deformation of the bone tissue [ 19 , 20 , 21 ]. It has proved an auspicious approach for measuring internal strains of bone under various loading conditions and offers a crucial method for validation of finite element (FE) models of bone [ 22 , 23 , 24 , 25 , 26 , 27 ].…”