Finite Element Representation of Bone-Screw Mechanics

Date of Award

3-2016

Document Type

Masters Thesis

Degree Name

M.S.

Organizational Unit

Daniel Felix Ritchie School of Engineering and Computer Science, Mechanical and Materials Engineering

First Advisor

Peter J. Laz

Keywords

Humerus fracture, Bone screws, Locking plates

Abstract

Proximal humerus fracture remains a major public health concern due to the large number of occurrences and is one of the leading causes of mortality especially among the elderly populations. Proximal humerus fracture is often caused by low energy falling directly on the shoulder or arm. Fixation using locking plates and bone screws has become the treatment of choice; however, an overall complication rate of 49% has been reported, with 7.5% resulted from failure of the bone-screw interface. Accordingly, the purpose of the work presented in this thesis is to develop finite element representations of the bone-screw mechanics. This computational model can be used to evaluate locking plate designs and screw placement configurations; it can be a cost effective alternative to expensive and labor intensive experimental testing.

Models of the bone screw interface were calibrated under screw pull-out, translational screw cut-out, and wiper screw cut-out loading conditions. A bone cube crush model was also created to calibrate material behavior. Modeled peak screw pull-out forces matched reasonably well with those from experiment, with an average difference of 11%. The cut-out models were able to generate comparable force-displacement behaviors. A unified representation, considering the various failure modes and using the optimized interface interaction parameters, was demonstrated in a full bone-implant construct model. Various loading conditions can be applied to the full bone-implant model to assess bone failure behaviors. The studies incorporated finite element techniques that allow researchers to observe bone-screw interface failures while maintaining relatively efficient computational time and accuracy.

Publication Statement

Copyright is held by the author. Permanently suppressed.

Rights Holder

Haixiang Sean Hu

Provenance

Received from author

File Format

application/pdf

Language

en

File Size

78

Discipline

Mechanical engineering, Biomechanics

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