umi-umd-4778 - ABSTRACT Title of Document: HUMERAL FRACTURE...

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ABSTRACT Title of Document: HUMERAL FRACTURE FIXATION TECHNIQUES: A FEA COMPARISON OF LOCKING AND COMPRESSION TECHNIQUES WITH CADAVERIC PULLOUT COMPARISON OF CORTICAL COMPRESSION AND INTERNAL LOCKING SCREWS. Aaron Johnson, MS Mechanical Engineering, 2007 Directed By: Professor, Donald Barker, Mechanical Engineering Locking and non-locking humeral repair techniques provide different mechanical constructs for securing fractures, and consequently could generate different strain fields at the callus. The purpose of this study was to investigate the strain field callus, and to compare to determine if one construct offers a healing advantage over another. An FEA analysis was conducted using ABAQUS, with all contact surfaces modeled as friction interfaces; additionally, a pretension was applied to the non-locking construct to simulate the effect of installation. The models were subjected to axial tension loads, and results were compared with existing cadaveric and synthetic experimental loading. Additional validation involved screw pullout testing conducted on cadaveric humeri. Results showed that the strain fields at the fracture site showed no significant variation in distribution, shape, or magnitude, therefore concluding that the locking plate offered no biomechanical healing advantage.
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HUMERAL FRACTURE FIXATION TECHNIQUES: A FEA COMPARISON OF LOCKING AND COMPRESSION TECHNIQUES WITH CADAVERIC PULLOUT COMPARISON OF CORTICAL COMPRESSION AND INTERNAL LOCKING SCREWS. By Aaron Joseph Johnson Thesis submitted to the Faculty of the Graduate School of the University of Maryland, College Park, in partial fulfillment of the requirements for the degree of Masters of Science, Mechanical Engineering 2007 Advisory Committee: Professor Donald Barker, Chair F. Patrick McCluskey, Associate Professor, Mechanical Engineering, CALCE EPSC Adam Hsieh, Assistant Professor, Bioengineering, Orthopedic Mechanobiology Laboratory
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© Copyright by Aaron Joseph Johnson 2007
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ii Acknowledgements Thanks to all those who helped in the process of completing the research associated with this thesis: Morrigan Johnson, for her sample polishing and general support Gilad Sharon and Nathan Blattau for modeling advise and assistance with FEA David Ryan for help with experimental design and testing Robert O’Toole, MD and Adam Hsieh for orthopedic, medical, and biomechanical guidance while developing the models contained herein.
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iii Table of Contents Acknowledgements. ...................................................................................................... ii Table of Contents. ........................................................................................................ iii List of Tables . .............................................................................................................. iv List of Figures. .............................................................................................................. v List of Figures. .............................................................................................................. v Introduction. .................................................................................................................. 1 Reasons for Study . .................................................................................................... 1 Background. .............................................................................................................. 2 Purpose. ..................................................................................................................... 3 Chapter 2: Methods. ...................................................................................................... 4 Material Properties and Model Dimensions . ............................................................ 4 Modeling Assumptions. ............................................................................................ 7 Model loading. ........................................................................................................ 14 Chapter 3: Model Validation . ..................................................................................... 15 Including Cadaveric bone screw pullout experiment. ............................................. 15 Introduction. ............................................................................................................ 15 Cadaveric bone screw pullout. ................................................................................ 15 Introduction. ........................................................................................................ 15 Background. ........................................................................................................ 16 Methods. .............................................................................................................. 21 Data / Results. ..................................................................................................... 24 Discussion. .......................................................................................................... 30 Chapter 4: FEA Results and Discussion. .................................................................... 32 Chapter 5: Conclusion and Discussion . ..................................................................... 34
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iv List of Tables Table 1. Screw Dimensions . ....................................................................................... 21 Table 2. Comparison of shear failure stresses .
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umi-umd-4778 - ABSTRACT Title of Document: HUMERAL FRACTURE...

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