Browsing by Author "Lanier, Amelia"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Differences in transverse knee moment in healthy, ACL-deficient, and ACL-reconstructed patients during standing target matching(University of Delaware, 2012) Lanier, AmeliaAnterior cruciate ligament (ACL) injury is a common injury affecting nearly 250,000 Americans a year (Boden et al. 2000). Reconstructive surgery costs add up to approximately $1.5 billion annually not including initial evaluation or post-operative rehabilitation (Boden et al. 2000). The anterior cruciate ligament (ACL) limits anterior tibial translation and internal tibial rotation and so in the absence of the ACL rotational instability is common. Transverse knee moment, which has not been the focus of much research, can determine ACL-deficient (ACL-d) subjects’ ability or inability to compensate for this rotational instability. Target matching, both standing and seated, has provided insight for understanding neuromuscular control in both ACL deficient and reconstructed patients via EMG measurements (Williams et al. 2003; Macleod et al. 2011). We are now beginning to look at kinetic measures like transverse knee moment during this task in healthy, ACL-d and ACL reconstructed patients. Therefore the first aim of this work was to investigate transverse knee moment measured during a neuromuscular task in a healthy population. There is no difference in transverse knee moment between the right and left limbs of healthy subjects during standing target matching. Additionally, the shear forces generated by the mobilizing limb strongly correlate with the transverse knee moment of the stabilizing limb. These results indicate kinetic measures produced during standing target matching are dictated by target matching role not the limb itself. The second aim of this work was to evaluate transverse knee moment measured during a neuromuscular task in ACL-d patients. Our results show those with ACL injury have significantly higher internal rotation moments than healthy uninjured subjects. Increased rotational loads are present when subjects generate medial shear forces. This indicates an area of interest and the importance of joint stability in this medial direction. The third and final aim of this work was to evaluate changes in transverse knee moment during a neuromuscular task in ACL reconstructed patients. In particular we tested subjects within six months to one year post reconstruction when re-injury risk is highest (Salmon et al. 2005; Paterno et al. 2012). From this study we found those who undergo ACL reconstruction produce higher internal rotation moments when compared to uninjured subjects. We also see increased rotational loading at medial targets. In our group of subjects it appears that increased rotational loading occurs after injury and is not mitigated by reconstruction. The resulting increase in joint loading may have implications for high re-injury rates seen post reconstruction (Hewett et al. 2012) and high rotational loads have already correlated with increased cartilage loss (Henriksen et al. 2012). Producing force in a medial direction may be dangerous for those with ACL injury even after reconstruction and could be used to identify those at higher risk of re-injury. These results provide a basis to explore rotational loading corresponding to different graft types while exploring possible interventions to create joint stability in this medial direction.Item Measuring changes to force control variability using Lyapunov exponents: looking at the influence of anterior cruciate ligament injury and reconstruction and high performance athletics(University of Delaware, 2016) Lanier, AmeliaRupture of the anterior cruciate ligament is a common sports related injury that results in significant financial burden. A significant amount of research has been conducted to understand function and recovery after ACL tears. Of particular interest, is understanding biomechanics of running and cutting maneuvers as these tasks lead to a majority of ACL tears. Recently, the use of nonlinear analysis techniques have provided promising results in a number of biomechanical applications. Specific to ACL injury, researchers using maximal Lyapunov exponents found significant changes to kinematic control at the knee. However, nonlinear kinetic changes that may occur after ACL injury have yet to be explored. The goals of this dissertation were to explore the use of nonlinear techniques as they relate to the control of multidirectional ground reaction forces in recreational athletes (uninjured controls), high performance athletes, ACL deficient patients, and ACL reconstructed patients and to evaluate how nonlinear measures relate to both injury mechanism and task performance. As a part of this dissertation we developed a force control task that utilizes real time visual feedback of a person's force production to understand force control variability, as measured by maximal Lyapunov exponents. For the first two aims the force control task was used to study recreational athletes, high performance athletes, ACL deficient individuals, and ACL reconstructed individuals. The third aim was divided into two parts, one which explored force control variability and ACL injury mechanism, and one which evaluated the relationship between force control variability and task performance. For the first part of aim 3, ACL deficient subjects were divided by injury mechanism, contact versus noncontact and LyE values were assessed. For the final part of this aim, high performance athletes completed a series of sport-like tasks including a cutting maneuver, a lateral shuffle, and a deceleration task and biomechanical data from these tasks were then correlated with LyE data from the force control task. From this work we found that recreational and high performance athletes had similar mGRF control in their right and left limbs. Recreational athletes additionally generated similar LyE in both the anterior/posterior (AP) and medial/lateral (ML) directions, while high-performance athletes generated lower LyE values in the ML direction indicating superior mGRF control in that direction. In our exploration of force control variability after ACL injury and reconstruction, we found significantly larger force control variability in both ACL-d and ACL-r subjects when compared to healthy controls and high performance athletes. This deficit in mGRF control may be a significant contributor to ACL re-injury as it may affect the ability to perform different running and cutting tasks. Those who experience a contact injury exhibit mGRF control deficits through LyE measures which suggests that secondary tissue commonly seen in contact injuries correlate with average stance time in all sport-like tasks tested. As LyE values increased, which indicates poor control, average stance time decreased. Understanding not only how mGRF control changes after ACL injury and reconstruction, but the dynamic interplay between LyE and injury mechanism and LyE and sports performance, helps biomechanists get a more complete picture of force control variability. This work can assist in developing new rehabilitation techniques and training programs that can not only enhance performance but improve injury recovery. Nonlinear analysis techniques have the potential to be a powerful addition to our current clinical knowledge base.