Browsing by Author "Edwards, W Brent"
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- ItemOpen AccessFour-Dimensional Computed Tomography to Determine Normal Syndesmotic Motion and to Compare Motion after Rigid and Flexible Fixation of Syndesmotic Injuries(2020-11-27) Wong, Murray T; Schneider, Prism S; Edwards, W Brent; Wiens, Charmaine AS; Manske, Sarah L; LaMothe, Jeremy MSyndesmotic injuries occur in up to one-quarter of all ankle fractures. Despite mitigating efforts, malreduction of the syndesmosis is common after both rigid and flexible fixation methods, causing inferior patient function. Conventional assessments of syndesmotic reduction do not account for normal syndesmotic motion with ankle range-of-motion (ROM). The aims of this thesis were to use four-dimensional computed tomography (4DCT) to determine normal syndesmotic motion and to investigate the impact of rigid and flexible fixation on postoperative syndesmotic kinematics. Fifty-eight uninjured ankles were imaged to quantify normal syndesmotic kinematics. Thirteen patients after rigid or flexible fixation underwent bilateral ankle 4DCT to evaluate postoperative syndesmotic kinematics. Measures of syndesmotic width including anterior, middle, and posterior syndesmosis distances as well as tibiofibular clear space and tibiofibular overlap were automatically extracted from 4DCT data. Sagittal translation and fibular rotation were also recorded. Linear mixed effects models were used to determine the position of the syndesmosis at neutral dorsiflexion as well as syndesmotic motion, defined as the change in syndesmotic measurements with ankle ROM.In uninjured ankles, various measures of syndesmotic width decreased by 0.7-1.1 mm as ankles moved from dorsiflexion to plantarflexion (p < 0.001). The fibula externally rotated by 1.2° with plantarflexion (p < 0.001). There was no significant motion in the sagittal plane (p = 0.43). Rigid fixation increased syndesmotic width compared to uninjured ankles when measured by middle syndesmotic distance and tibiofibular clear space only (p = 0.039 and 0.032 respectively). Rigid fixation demonstrated reduced motion compared to uninjured ankles in middle and posterior syndesmotic distance, tibiofibular clear space, and tibiofibular overlap (p < 0.01). There were no differences in syndesmotic position or motion between flexible fixation and uninjured ankles.Ankle plantarflexion leads to decreased syndesmotic width and fibular external rotation in uninjured ankles, indicating ankle position must be accounted for when performing syndesmotic imaging and fixation. Flexible fixation better restores syndesmotic position and motion compared to rigid fixation. These findings may be used to decrease the rate of syndesmotic malreduction and, consequently, improve post-surgical outcomes.
- ItemOpen AccessAn Inverse Interface Evolution Problem to Identify Participant-Specific Bone Microarchitecture Adaptation(2021-05-13) Kemp, Tannis Danielle; Boyd, Steven; Zinchekno, Yuriy; Bertram, John; Edwards, W BrentBone’s microarchitecture, strength and density change throughout our lifetime through the natural process of bone adaptation. With age, the mechanisms that normally maintain bone’s mechanical competence are disrupted and rapid bone loss ensues. In an attempt to understand these mechanisms, many theories and computational models were developed. But to date, few of these models have been rigorously tested in vivo. The first objective of this thesis was to develop a computational technique to validate bone adaptation models in vivo. Specifically, an inverse problem was defined that identifies participant-specific bone adaptation parameters from high-resolution computed tomography (CT) image data of changing bone microarchitecture. The inverse problem was based on a model of advection and mean curvature flow (curvature-driven bone adaptation). The inverse technique was accurate for synthetic data that exactly obeyed the curvature-driven model; it was insensitive and robust to small amounts of salt-and-pepper. Based on a solver that was accurate for data that obeyed the curvature-driven model, it was possible to test the model itself on longitudinal in vivo data. Sixteen astronauts who spent between four and seven months on the International Space Station received high-resolution peripheral quantitative computed tomography (HR-pQCT) scans before and after flight. The inverse problem was solved for each participant, and bone samples were simulated to match the HR-pQCT images at each measurement. Predicted and observed static morphometry (trabecular thickness, separation, number and bone volume fraction) agreed well, but dynamic morphometry (bone formation and resorption rates) indicated a poor fit. While the mean curvature model did not predict local bone adaptation in astronauts, a framework was developed that will allow researchers to test any model in vivo on a participant-specific basis. The inverse problem is versatile and general and could easily be adjusted for other models (i.e., strain-driven or other geometric flows). By rigorously testing hypotheses regarding bone adaptation in vivo, researchers will better understand the mechanisms of bone loss in space and on Earth.
- ItemOpen AccessLower-limb joint kinetics in jump rope skills performed by competitive athletes(Routledge, 2020-08-28) Bruce, Olivia L; Ramsay, Mollee; Kennedy, Geneva; Edwards, W BrentThe purpose of this study was to characterise lower-limb joint kinetics during consecutive double unders and speed step sprints performed by competitive jump rope athletes, and to compare these measurements to running. Sixteen adolescent competitive jump rope athletes performed consecutive double under, speed step, and running trials while motion capture and ground reaction force data were collected. Lower-limb joint moments, power, and work were calculated using an inverse dynamics approach and discrete measurements were compared between skills. Peak ground reaction forces were similar between movements; however, knee and hip joint kinetics were distributed differently between double unders and speed step. In general, double unders were characterised by an increased reliance on knee joint kinetics, while speed step was characterised by an increased reliance on hip joint kinetics. Peak ankle moments were 9-20% greater in speed step when compared to double unders and running (p ≤ 0.050), and peak negative ankle power was 39-114% greater in double unders and speed step when compared to running (p ≤ 0.002). These findings may have important implications for injury risk and load management in jump rope athletes or other individuals that incorporate jump rope into their training programs.
- ItemOpen AccessA statistical shape model of the tibia-fibula complex: sexual dimorphism and effects of age on reconstruction accuracy from anatomical landmarks(2021-11-03) Bruce, Olivia L; Baggaley, Michael; Welte, Lauren; Rainbow, Michael J; Edwards, W BrentA statistical shape model was created for a young adult population and used to predict tibia and fibula geometries from bony landmarks. Reconstruction errors with respect to CT data were quantified and compared to isometric scaling. Shape differences existed between sexes. The statistical shape model estimated tibia-fibula geometries from landmarks with high accuracy (RMSE = 1.51-1.62 mm), improving upon isometric scaling (RMSE = 1.78 mm). Reconstruction errors increased when the model was applied to older adults (RMSE = 2.11-2.17 mm). Improvements in geometric accuracy with shape model reconstruction changed hamstring moment arms 25-35% (1.0-1.3 mm) in young adults.
- ItemOpen AccessTibial-fibular geometry and density variations associated with elevated bone strain and sex disparities in young active adults(Elsevier, 2022-05-20) Bruce, Olivia L; Baggaley, Michael; Khassetarash, Arash; Haider, Ifaz T; Edwards, W BrentTibial stress fracture is a common injury in runners and military personnel. Elevated bone strain is believed to be associated with the development of stress fractures and is influenced by bone geometry and density. The purpose of this study was to characterize tibial-fibular geometry and density variations in young active adults, and to quantify the influence of these variations on finite element-predicted bone strain. A statistical appearance model characterising tibial-fibular geometry and density was developed from computed tomography scans of 48 young physically active adults. The model was perturbed ±1 and 2 standard deviations along each of the first five principal components to create finite element models. Average male and female finite element models, controlled for scale, were also generated. Muscle and joint forces in running, calculated using inverse dynamics-based static optimization, were applied to the finite element models. The resulting 95th percentile pressure-modified von Mises strain (peak strain) and strained volume (volume of elements above 4000 με) were quantified. Geometry and density variations described by principal components resulted in up to 12.0% differences in peak strain and 95.4% differences in strained volume when compared to the average tibia-fibula model. The average female illustrated 5.5% and 41.3% larger peak strain and strained volume, respectively, when compared to the average male, suggesting that sexual dimorphism in bone geometry may indeed contribute to greater stress fracture risk in females. Our findings identified important features in subject-specific geometry and density associated with elevated bone strain that may have implications for stress fracture risk.