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Alex Glass-Hardenbergh and Grace Heidelberger

Modeling Interfragmentary Strains to Predict Healing of Bone Fractures

Department: Mechanical Engineering and Mechanics
Advisor: Hannah Dailey

View: UGRS Research Poster (PDF)

For tibial (shinbone) fractures, nonunion (failure to heal) occurs in about 4% of simple closed fractures and nearly 50% of very severe open fractures. Computational and animal models have shown that the local mechanical strains within the healing zone determine healing outcomes, but no previous studies have investigated the role of the three-dimensional fracture geometry in determining these strains or the risk of nonunion. In this study, we created idealized models of a transverse, oblique, spiral, and wedge fractures. Finite-element (FE) models were generated in ANSYS Mechanical, with applied axial compression and torsion loading conditions derived from test data from commercial bone fixation devices.  Linear elastic material properties were chosen from literature values for the cortical bone and surrounding callus (healing zone). The FEA simulations generated dilatational and distortional strains within the fracture zone and post-processing in MATLAB sorted elements according to likely tissue type evolution using previously-published mechanical strain thresholds. The results showed that peak strains were highest in the most geometrically complex fracture models (spiral) and these models were also most sensitive to torsional motion. Torsional instability strongly influenced the type of tissue predicted to form in the callus (bone, cartilage, or fibrous tissue) and that all fracture types had increasing tissue destruction with increasing torsion. This suggests that in addition to biological and patient factors, fracture geometry may contribute to the risk of nonunion.

About Alex Glass-Hardenbergh:
Alex Glass-Hardenbergh is pursuing a degree in dual degree in Mechanical Engineer and Integrated Business & Engineering in Finance.  He is a Dean’s List student, a member of Tau Beta Pi Engineering Honors Fraternity, and a member of Pi Tau Sigma International Honorary Mechanical Engineering Society.  Since 2010, Alex has been a volunteer fire fighter for Hillsborough Volunteer Company #3 and has completed 138 hours of interior and exterior training.  At Lehigh, Alex is a member of Lehigh’s club soccer team, snowboarding club, and Engineers Without Borders.  During the summer of 2013, he worked at Johnson & Johnsons World Wide Engineering & Technical Operations improving air pollution control equipment across the enterprise.  The following summer, Alex worked at JPMorgan in the Treasury Services Foreign Exchange Payment Products team assisting the pricing migration roll out strategy.  Alex is a graduate of the Lehigh Silicon Valley 2015 Program, an immersion program in entrepreneurship and venture capital.  He has performed extensive research in the mechanics of fracture healing and the Czech Republic’s Electricity infrastructure.  After college, Alex is interest in pursuing a career in consulting.

About Grace Heidelberger:
Grace Heidelberger, is a Junior at Lehigh University pursuing a B.S. in Mechanical Engineering with an Applied Mathematics minor. She began research with Professor Dailey in 2015, working to develop a correlation between torsional instability during bone healing and the type of tissue predicted to form. She plans on continuing her education with graduate school to pursue a PhD in Biomechanical Engineering. In addition to her school work, she is a co-captain of the club basketball team, an Admission Ambassador, and a tutor.