Development of a Biplanar Fluoroscopy System for Characterizing in vivo Foot and Ankle Biomechanics

Abstract

Precise quantification of lower extremity skeletal kinematics during functional tasks is paramount to impactful foot biomechanics research. Skin motion artifact errors associated with motion capture and bony occlusions present in sagittal radiographic imaging approaches limit the ability of biomechanists to apply these respective techniques to the forefoot. A custom biplane system for dynamic imaging of the entire foot and ankle complex during gait is presented as a solution to this challenge. In addition to detailing the imaging chain hardware, the necessary software for preprocessing the data and performing marker-based and model-based tracking from the stereo fluoroscopy images is described. Further, this dissertation explores the accuracy of foot bone models generated from computed tomography scans, comparing the performance of cone beam and fan beam scanners. The findings support the adoption of low-dose cone beam weight-bearing computed tomography for 3D modeling of foot and ankle bones and for generating the digitally reconstructed radiographs needed for model-based tracking of gait trials. The morphology and motion of the first ray are quantified using weight-bearing computed tomography to provide data for a standardized first metatarsophalangeal joint coordinate system for the biomechanics community. Finally, this dissertation explores the feasibility of indirectly assessing the intricate biomechanical behavior of the plantar soft tissues of the foot as a natural shock absorber and load-bearing interface by tracking the calcaneus. The spatial and temporal resolutions afforded by biplane fluoroscopy coupled with the methods outlined in this work will contribute to advancing the field of lower extremity biomechanics, as these kinematic data underpin various clinical investigations of in vivo function.