PhD student Matthew MacEwen successfully defends dissertation

December 6, 2024 — University of Minnesota Biomedical Engineering PhD student Matthew MacEwen successfully defended his dissertation, "Dynamic, Multiscale Assessment of Lumbar Functional Spinal Unit Biomechanics during Physiologic Motion" this week. He was advised by Assistant Professor Arin Ellingson, and co-advised by Professor Victor Barocas.

Following is an abstract of his dissertation:

Low back pain affects approximately 80% of Americans over their lifetime and remains challenging to diagnose due to the complex interplay of anatomical structures and biomechanical forces in the lumbar spine. Many contributors to LBP are exacerbated by the mechanical demands of lumbar intersegmental motion, underscoring the need for a deeper understanding of these dynamic interactions. This thesis investigates the spine’s response to dynamic loading across multiple scales by developing and applying innovative analytical tools to address critical gaps in spinal biomechanics. At the macroscale, the Dynamic Compliance Vector (DCV) was developed as a novel framework to quantify dynamic kinetic responses during complex, multi-planar motions. Cadaveric testing revealed flexion exhibited the greatest compliance and axial rotation the lowest, with significant compliance reductions near the end range of motion. The Kemp’s test, a clinically significant multiplanar motion, emerged as a distinctive diagnostic tool, combining lateral bending and axial rotation to reveal key aspects of lumbar motion dynamics. At the microscale, an enhanced digital image correlation protocol quantified facet capsular ligament (FCL) strain under dynamic loading. Flexion produced the highest strain and most aligned strain fields, while the Kemp’s test uniquely isolated ipsilateral strain under minimal joint compression, further validating its clinical utility for diagnosing facetogenic pain. The findings of this thesis connect macroscale and microscale analyses to deepen our understanding of lumbar spine biomechanics and improve diagnostic approaches.