Area:
Mechanical Engineering, Recreation, Biomechanics Biophysics, Surgery
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High-probability grants
According to our matching algorithm, Edward M. Wojtys is the likely recipient of the following grants.
Years |
Recipients |
Code |
Title / Keywords |
Matching score |
2007 — 2009 |
Wojtys, Edward M |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Effect of Component Impulsive Loading On Relative Acl Strain @ University of Michigan At Ann Arbor
[unreadable] DESCRIPTION (provided by applicant): Anterior cruciate ligament (ACL) injuries of the knee frequently alter the lifestyle of active people. Recently, the long-term consequences of these injuries have become clearer regardless of the treatment chosen. Degenerative arthritis is the most common outcome, occurring in as little as seven years post injury (Pinczewski 2002). With an estimated 300,000 ACL tears surgically treated in the U.S. in 2005 (AOSSM 2006) there is a need to better prevent these injuries. This proposal addresses the urgent need to better understand the mechanism of ACL injury in hopes of improving both risk factor surveillance and prevention programs. Many ACL injuries occur when landing on one foot from a jump or when running and cutting. There are no systematic studies of how the direction of the impulsive loading affects ACL strain. We plan to use a cadaver construct to first determine how ACL strain is affected by the direction of an impulsive load that applies both compression and a moment to the knee joint. The knee will initially be constrained at an initial angle of 15[unreadable] via pretensioned quadriceps, medial and lateral hamstring and gastrocnemius muscle- equivalents, but the knee can flex under load. In AIM 1 we will test the hypothesis that a 2*BW impulsive force that applies valgus, internal or external axial rotation moments to the knee will increase peak ACL strain compared with a sagittally-symmetric loading involving an equivalent flexion-only moment. In AIM 2 we will test the hypothesis that superposition of the AIM 1 valgus and axial rotation moment components results in greater peak ACL strain than a flexion moment of similar magnitude. In AIM 3 the hypothesis will be tested that there is a higher risk for ACL rupture under a 4*BW impulsive loading with an out-of-sagittal plane loading component than with sagittally-symmetric loading. In AIM 4 we will test the hypothesis that peak ACL strain can be reduced by stretch of the hamstring muscle-equivalents as the knee flexes in response to impulsive loading. Pilot data suggest that such stretch can be induced when adequate hip flexion accompanies the knee flexion associated with a jump landing; absence of such stretch results in increased ACL strain. Three hypotheses will be tested using paired knees in a repeated measures design. Load transducers will be used to measure the 3-D impulsive loading above and below the knee, and muscle forces will be measured using load cells. 3-D kinematics of the femur and tibia will be measured using the Certus system. ACL relative strain will be measured using a differential variable reluctance transducer. Up to 120 cadaver knees will be used. [unreadable] [unreadable]
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1 |
2010 — 2012 |
Wojtys, Edward M |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Effect of 3-D Compound Impulsive Loading On Relative Acl Strain
DESCRIPTION (provided by applicant): This proposal addresses a current knowledge gap: why women are 2 to 8-fold more susceptible to ACL injury than men. Many ACL injuries occur when landing on one foot from a jump or when running and cutting. In Years 01-03 we used an instrumented cadaver construct to identify the direction of the impulsive compound 3-D loading that causes the largest peak ACL strain: compression + flexion moment + internal tibial axial torque. We now seek funds to use this cadaver testing construct, complete with non-linear quadriceps tensile stiffness, to determine the effect of gender on peak ACL relative strain under the above compound impulsive loading scenario. Each knee will initially be positioned at an initial flexion angle of 15 degrees via pretensioned quadriceps, medial and lateral hamstring and gastrocnemius muscle-tendon equivalents that allow the knee to flex under the impulsive load. In AIM 1 we will test the hypothesis in 22 male and female knees from size-matched cadavers that gender does not affect the peak ACL relative strain due to a 2*BW impulsive force and the above compound impulsive loading. Pilot data suggest ACL strain is larger in female knees. In AIM 2, to further delineate the injury mechanism, we will use a repeated measures design and 22 size-matched knees to test the hypothesis that medially-dominant quadriceps and hamstring knee muscle forces significantly increase peak ACL relative strain compared to laterally-dominant muscle forces, especially in females. Pilot data suggest this to be the case. In AIM 3 we will use a repeated measures design to test the hypothesis in 10 knees that swapping out the female quadriceps muscle-equivalent with a stiffer male counterpart will significantly reduce the peak ACL strain in the female knee under the compound impulsive loading;in 10 male knees the corresponding effect will not achieve significance. Pilot data suggest this is indeed the case. Insights from this research will help address the urgent need to better understand the role of gender in the mechanism of ACL injury to improve both risk factor surveillance and prevention programs. PUBLIC HEALTH RELEVANCE: The goal of this research is to better understand the mechanisms causing ACL injuries to be more common in women than men. Given the smaller cross-sectional area of the female ACL, in AIM 1 we will use fully instrumented cadaver knees to test the hypothesis that the peak ACL strain during a simulated jump landing is larger in females than males of the same size. In AIM 2 we will test the hypothesis that this strain is elevated in the female when the muscle forces crossing the knee on the inside and outside of the leg are not balanced. In AIM 3 we will test the hypothesis that increasing the tensile stiffness of the female quadriceps muscle significantly reduces peak ACL strain. Insights from this research should be useful for improving the efficacy of prevention programs designed to reduce the risk of ACL injury, particularly in females.
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1 |
2016 — 2021 |
Ashton-Miller, James Anthony (co-PI) [⬀] Wojtys, Edward M |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
New Perspectives On Acl Injury
Abstract This proposal challenges the current dogma that `non-contact' anterior cruciate ligament (ACL) ruptures are due to sudden awkward landing or overload event. In the past funding cycle we developed the first evidence that the ACL can also fail under repetitive sub-maximal loading (Lipps 2013), helping to explain why an ACL can fail during a routine athletic maneuver. Pilot data suggest that this fatigue failure is associated with an accumulation of microdamage near the proximal femoral enthesis. We request funds to test this hypothesis. In AIM 1 60 pairs of knees from sex- and size-matched younger cadavers (30 males, 30 females) will be positioned at an initial flexion angle of 15o via pretensioned knee muscle-tendon equivalents that allow the knee to flex under a distal impulsive test load. ACL fatigue life will be determined via repetitive sub-maximal four-times bodyweight impulsive 3-D compound loading (compression + trans knee muscle loading + flexion moment + knee abduction moment + internal tibial axial torque) applied to each knee. A Cox regression model will be used to rank the relative importance of sex, internal femoral axial rotation range of motion (ROM) and lateral tibial slope in limiting ACL fatigue life. In AIM 2a we will use histological images and a binomial exact test to determine the percentage of the knees undergoing AIM 1 fatigue testing that exhibit microdamage at or near the femoral enthesis exceeding the +3*SD area found in the 32 untested, paired, control knees. Similarly, in AIM 2b we will salvage ACL femoral enthesis explants in 60 healthy young adults (30 females) aged 14-25 years undergoing routine reconstruction of their ACL and determine the percentage of explants exhibiting microdamage area exceeding the +3*SD value measured in 30 untested age- and sex-matched cadaveric controls. If greater-than-normal ACL microdamage is found in fatigue-tested knees in vitro (AIM 2a) and in ACL-injured patients in vivo (AIM 2b) this suggests the ACL can fail due to an accumulation of fatigue damage. This would imply that there may be time to modify athlete work-rest cycles to reduce ACL injury risk by arresting the injury cycle (Olsen 2006) and allowing the ACL to heal (Maekawa 1996).
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1 |