Date of Award
Doctor of Philosophy (PhD)
Harris, Gerald F.
Lower extremity motion analysis has become a powerful tool used to assess the dynamics of both normal and pathologic gait in a variety of clinical and research settings. Early rigid representations of the foot have recently been replaced with multi-segmental models capable of estimating intra-foot motion. Current models using externally placed markers on the surface of the skin are easily implemented, but suffer from errors associated with soft tissue artifact, marker placement repeatability, and rigid segment assumptions. Models using intra-cortical bone pins circumvent these errors, but their invasive nature has limited their application to research only. Radiographic models reporting gait kinematics currently analyze progressive static foot positions and do not include dynamics.
The goal of this study was to determine the feasibility of using fluoroscopy to measure in vivo intra-foot dynamics of the hindfoot during the stance phase of gait. The developed fluoroscopic system was synchronized to a standard motion analysis system which included a multi-axis force platform. Custom algorithms were created to translate points of interest from 2D fluoroscopic image space to global tri-axial space. From these translated points of interest, a hindfoot specific model was developed to quantify sagittal plane talocrural and subtalar dynamics.
The new hindfoot model was evaluated and applied to a pilot population of thirteen healthy adults during barefoot and toe-only rocker walking conditions. The barefoot kinematic and kinetic results compared favorably with barefoot dynamics reported by other authors. As a result of the barefoot study, it was concluded that inter-subject variability in sagittal plane kinematics was higher for the talocrural joint than the subtalar joint. The toe-only rocker analysis was the first report of hindfoot kinematics within a rocker sole shoe modification. Hindfoot kinematic inter-subject variability was significantly lower in the toe-only rocker condition when compared to barefoot results.
This study represents the first use of fluoroscopy to quantify in vivo intra-foot dynamics during the stance phase of gait. Talocrural and subtalar dynamics of healthy adult subjects are reported. The technology developed for this study is capable of examining soft tissue and bony abnormalities associated with the pathologic foot. Based on the overall results of this study, it is recommended that development continue for further analysis within the clinical environment, and examination of complex in vivo foot and ankle dynamics.