Date on Master's Thesis/Doctoral Dissertation

5-2018

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Bioengineering

Committee Chair

Bertocci, Gina

Committee Co-Chair (if applicable)

Thompson, Angela

Committee Member

Frieboes, Hermann

Committee Member

Voor, Michael

Author's Keywords

pediatric femur fracture; child abuse; in-silico femur model; finite element analysis

Abstract

Bone fracture is the second most common injury of child abuse. Studies have generally reported that femur fractures are more likely due to abuse than accidental causes in cases where the child is non-ambulatory. They have also found that household falls are commonly offered as the cause of injury in cases of abuse. In this study, a finite element (FE) pediatric femur model will be developed and used to evaluate likelihood of fracture in common household fall scenarios (bed falls and feet first falls). This will provide greater biomechanical evidence as to the likelihood of femur fracture due to common fall scenarios which may serve to better inform clinicians when assessing compatibility between stated cause and injury when household falls are reported. The purpose of this study is to determine the likelihood of fracture of a 12-month-old child’s femur due to commonly reported accidental fall scenarios using finite element analysis. Loading conditions in the FE model were derived from femur loads reported in a previously study measured using a 12-month old anthropomorphic test device (ATD) in experimentally simulated household falls. A FE femur model was derived from a CT scan performed on an 11-month old child. Validation of the FE model was conducted through mechanical testing of a bone surrogate printed using selective laser sintering of glass-fiber reinforced nylon. The finite element model used simple support for the constraints and the loads from the ATD study were applied at the corresponding location of the load cells, which bounded the diaphysis of the femur. The FE predicted outcomes including maximum principal stress and strain values were used to evaluate the likelihood of fracture by comparing to three different thresholds: (1) tensile yield strain, (2) ultimate tensile strength, and (3) ultimate flexural strength. Fifty-percent of bed falls exceeded the yield strain and ultimate tensile strength fracture threshold whereas only two (of 12) exceeded the flexural strength fracture threshold. Different bed fall dynamics considered resulted in a significant difference in peak strains while impact surface did not. Peak strains in bed falls were associated with the peak bending moment. No feet-first falls exceeded fracture thresholds. Fall height resulted in a significant difference in peak strains while the impact surface did not. Peak strains in feet-first falls were associated with the peak bending moment or torsional loads.

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