Finite Element Analysis Of Pull-Out Performance Of Bone Screw
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Date
2022-07-25
Authors
Tan, Yong Quan
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
In orthopaedic surgery, bone screws were frequently used in open reduction
internal fixation (ORIF) to keep the broken bones in place by screw’s compression force
to cure the bone fracture. It was critical to thoroughly examine its parameters, especially
the pull-out strength, to accelerate bone healing and minimise additional injury.
Previous studies focused on bone properties, screw design, and insertion techniques of
bone screw, through experimental or computational approach. The insertion angle of
bone screw was often mentioned as one of the potential parameters influencing pull out strength of the bone screw, yet it had received comparatively little attention and was
not the key element on any research particularly with numerical approach. The purpose
of this project was to numerically examine the effect of insertion angle of bone screw
on its axial pull-out strength. The stress-strain field after the screw insertion and
residual field after the screw pull-out were examined and analysed. 3-dimensional finite
element (3D FE) model of a cortical bone and solid rigid polyurethane foam block were
modelled and were computational simulated for pull-out test complying ASTM F543
standards. The total deformation, equivalent elastic strain, and equivalent stress were
evaluated from the simulation results for both the screw insertion and pull-out. The
pull-out force of the screw inserted into synthetic human bone was measured. The study
concluded that the increase in bone screw insertion angle will reduce the pull-out
strength. The stress-strain distribution was concentrated at screw-block contact zone
after the insertion, providing better fixation to the screw despite having lesser contact
volume at high insertion angle, leading to insignificant improvement. The residual field
of the foam block after the bone screw was pulled out promoted bone cure.