Regional White Matter Diffusion Changes Associated with the Cumulative Tensile Strain and Strain Rate in Non-concussed Youth Football Players

2021 ◽  
Author(s):  
James Holcomb ◽  
Ryan A. Fisicaro ◽  
Logan E. Miller ◽  
Fang F Yu ◽  
Elizabeth M. Davenport ◽  
...  
Keyword(s):  
White Matter ◽  
Strain Rate ◽  
Tensile Strain ◽  
Football Players ◽  
Youth Football ◽  
Strain And Strain Rate

scholarly journals Repetitive Head Impacts in Youth Football: Description and Relationship to White Matter Structure

2019 ◽  
Vol 11 (6) ◽  
pp. 507-513 ◽  
Author(s):  
Kurt J. Nilsson ◽  
Hilary G. Flint ◽  
Yong Gao ◽  
Leslie Kendrick ◽  
Steve Cutchin ◽  
...  
Keyword(s):  
White Matter ◽  
Diffusion Tensor ◽  
Brain Magnetic Resonance Imaging ◽  
The Body ◽  
Football Players ◽  
Head Impacts ◽  
Number Magnitude ◽  
Youth Football ◽  
Total Magnitude ◽  
Tackle Football

Background: Few studies have examined white matter with diffusion tensor imaging in 8- to 12-year-old collision sport (CS) athletes. Hypothesis: Youth CS athletes will demonstrate change in brain fractional anisotropy (FA) after a season of CS compared with an age-matched noncollision sport (NCS) cohort, and the number, magnitude, and location of hits will correlate with changes in the brain determined via FA for CS athletes. Study Design: Prospective cohort study. Level of Evidence: Level 3. Methods: Thirty-five 8- to 12-year-old males in a youth tackle football league (CS) and 12 males from local swim teams (NCS) were recruited. Participants underwent brain magnetic resonance imaging with FA before and after the football season. Number, magnitude, and direction of head impacts were recorded for CS participants throughout the season. Results: A total of 1905 hits were recorded in the CS group for the season, 341 (17.9%) collected during 7 games and 1564 (82.1%) observed during 31 practices. No significant interaction between group (CS and NCS) and time (pre- and postseason) was observed for FA ( P > 0.05). Correlation analysis revealed a significantly positive and moderate relationship between increase of left cingulate cortex (CgC) FA from pre- to postseason and the total magnitude of lateral head impacts ( r = 0.40; P = 0.03). Conclusion: There was no significant change in FA measurement of white matter integrity in a cohort of 8- to 12-year-old males after a season of youth football, nor was any difference detected in FA between youth football players and an age-matched cohort of swimmers. There was a significant correlation between total magnitude of hits sustained by youth football players and an increase in FA in the left CgC; whether this is adaptive or pathologic remains unknown. Clinical Relevance: These data can be used within the body of knowledge to counsel patients regarding the known risks of youth tackle football regarding brain health.

Macro-Micro Biomechanics Finite Element Modeling of Brain Injury Under Concussive Loadings

2016 ◽  
Author(s):  
X. Gary Tan ◽  
Andrzej J. Przekwas ◽  
Raj K. Gupta
Keyword(s):  
Finite Element ◽  
Brain Injury ◽  
White Matter ◽  
Strain Rate ◽  
Material Behavior ◽  
Tau Proteins ◽  
Beam Model ◽  
Strain And Strain Rate ◽  
Starting Point ◽  
Macro Scale

Traumatic brain injury (TBI) occurs in many blunt, ballistic and blast impact events. During trauma axons in the white matter are especially vulnerable to injury due to the rapid mechanical loading of brain. The axonal pathology leads to cytoskeletal failure and disconnection. The microtubules are one of major structural components of the cytoskeleton filamentous network. By bridging the macroscopic forces acting on the whole brain with the cellular and subcellular failure, the macro-micro computational models in both time and space can help us better understand the complex biophysics and elucidate the injury mechanism of both severe and mild TBI (concussion). At the macroscopic scale we developed the high-fidelity anatomical human body finite element model (FEM) to predict intracranial pressures and strain and strain rate fields of brain in the blast event. The macro-scale models and the coupled blast and biomechanics approach were validated against test data of shock wave interacting with a surrogate head in the shock tube. The mechanical deformation of brain tissue was mapped to the white matter tracts to obtain local axonal strain and strain rate for the micromechanical models. We developed the micromechanical FEM of myelinated axons interconnected with the oligodendrocyte by the processes, utilizing a novel beam element free of rotational degrees of freedom (DOFs). The numerical results reveal the possible mechanism of impact-induced axon injury including demyelination, breakup of processes, and axonal varicosity. We also investigate the dynamic response of microtubules bundles under traumatic loading. Different from the commonly discrete bead-spring models, a network of microtubules cross-linked with microtubule-associated-protein (MAP) tau proteins was modeled by the nonlinear beam model. Tau protein is modeled by the rate-dependent bar element for its complicated material behavior. The model considers the rupture of microtubule and the failure of tau-tau interface and tau-microtubule interface. The simulation result of the combined effects of the failure of the cross-linked architecture and elongation and bending of the bundle are possibly correlated to the axonal undulations following traumatic loading observed in the experiments. The developed macro-micro biomechanics models can be used as a starting point for modeling the neurobiology effects and guide the design of novel injury protection strategies.

scholarly journals Analysis of longitudinal head impact exposure and white matter integrity in returning youth football players

2021 ◽  
pp. 1-10
Author(s):  
Mireille E. Kelley ◽  
Jillian E. Urban ◽  
Derek A. Jones ◽  
Elizabeth M. Davenport ◽  
Logan E. Miller ◽  
...  
Keyword(s):  
White Matter ◽  
Diffusion Tensor ◽  
Mean Diffusivity ◽  
Head Impact ◽  
Cumulative Exposure ◽  
Control Group ◽  
Football Players ◽  
Imaging Data ◽  
Practice Session ◽  
Youth Football

OBJECTIVE The objective of this study was to characterize changes in head impact exposure (HIE) across multiple football seasons and to determine whether changes in HIE correlate with changes in imaging metrics in youth football players. METHODS On-field head impact data and pre- and postseason imaging data, including those produced by diffusion tensor imaging (DTI), were collected from youth football athletes with at least two consecutive seasons of data. ANCOVA was used to evaluate HIE variations (number of impacts, peak linear and rotational accelerations, and risk-weighted cumulative exposure) by season number. DTI scalar metrics, including fractional anisotropy, mean diffusivity, and linear, planar, and spherical anisotropy coefficients, were evaluated. A control group was used to determine the number of abnormal white matter voxels, which were defined as 2 standard deviations above or below the control group mean. The difference in the number of abnormal voxels between consecutive seasons was computed for each scalar metric and athlete. Linear regression analyses were performed to evaluate relationships between changes in HIE metrics and changes in DTI scalar metrics. RESULTS There were 47 athletes with multiple consecutive seasons of HIE, and corresponding imaging data were available in a subsample (n = 19) of these. Increases and decreases in HIE metrics were observed among individual athletes from one season to the next, and no significant differences (all p > 0.05) in HIE metrics were observed by season number. Changes in the number of practice impacts, 50th percentile impacts per practice session, and 50th percentile impacts per session were significantly positively correlated with changes in abnormal voxels for all DTI metrics. CONCLUSIONS These results demonstrate a significant positive association between changes in HIE metrics and changes in the numbers of abnormal voxels between consecutive seasons of youth football. Reducing the number and frequency of head impacts, especially during practice sessions, may decrease the number of abnormal imaging findings from one season to the next in youth football.

scholarly journals REPETITIVE HEAD IMPACTS IN YOUTH FOOTBALL: DESCRIPTION AND RELATIONSHIP TO WHITE MATTER STRUCTURE

2019 ◽  
Vol 7 (3_suppl) ◽  
pp. 2325967119S0000
Author(s):  
Kurt Nilsson
Keyword(s):  
White Matter ◽  
Football Players ◽  
Average Weight ◽  
Average Height ◽  
Head Impacts ◽  
Repetitive Head Impacts ◽  
Number Magnitude ◽  
Youth Football ◽  
Total Magnitude ◽  
Tackle Football

Background: A growing body of evidence has suggested that repetitive head impacts (RHIs) in collision sports produce changes in white matter tracts of athletes as detected by diffusion tensor imaging (DTI). Few studies have examined DTI in 8-12 year old collision sport (CS) athletes, compared them to non-collision sports (NCS) athletes, and correlated findings to accelerometry data. We sought to explore whether, after a single season of participation in youth football, 8-12 year old male CS athletes will: 1) have change in DTI fractional anisotropy (FA) of commonly injured brain regions, 2) have FA differences when compared to an age-matched NCS cohort, and 3) whether there is a correlation between FA and number, magnitude, and location of impacts. Methods: Thirty five 8-12 year old male participants in an organized youth tackle football league were recruited (CS) and matched with twelve 8-12 year old male participants in a local swim team (NCS). Each cohort underwent brain MRI with FA at 5 regions of interest (ROIs) before the youth football season and again immediately following the football season. CS participants’ helmets were instrumented with a force switch sensor to record number, magnitude, and direction of head impacts throughout a single season. Descriptive statistics were calculated for age, height, weight, FA values in all DTI ROIs (Anterior Corona Radiata (ACR), Cingulate Cortex (CgC), Genu of the Corpus Collosum (gCC), Posterior Limb of the Internal Capsule (pllC) and Splenium of the Corpus Collosum (SCC)), magnitude of head impact recorded by accelerometry by season, game and practice, number of hits by season, game and practice and by direction (top, side and rear). A mixed model (group by time) repeated measures MANOVA was conducted to determine if there were any differences in FA between the CS group and the NCS group from pre- to post-season. Correlation and regression analyses were carried out to determine if there was a relationship between the changes of FA from pre- to post-season and number and magnitude of head impacts in the CS group. Results: The average age of participants was: CS: 10.11 years, NCS: 10.17 years. The average height of participants was: CS: 56.89±4.06 inches; NCS: 59.92±5.00 inches (p=0.04). The average weight was: CS: 84.23±21.51 lbs; NCS: 84.75±24.04 lbs, (p>0.05). A total of 1905 hits were recorded for 34 participants in the CS group for the season, 341 (17.9% of total) collected during 7 games and 1564 (82.1% of total) observed during 31 practices. A total of 301 impacts (15.8% of total) with magnitude >= 80 g were collected. For brain ROIs investigated with FA, no significant interaction between group (CS and NCS) and time (pre to post season) was observed (p>0.05). Correlation analysis revealed a significantly positive and moderate relationship between increase of left CgC FA from pre to post season and the total magnitude of lateral head impacts (r=0.40, p=0.03). Conclusion: Our cohort of 8-12 year old male football players sustained fewer impacts when compared to prior accelerometry studies on youth football, although there was a larger number of higher force impacts recorded. There was no significant change in FA measurement of white matter integrity in our youth football players after a single football season, nor was there any difference detected in FA between youth football players and an age-matched cohort of swimmers. There was a significant correlation between total magnitude of hits sustained by youth football players during the season and an increase in FA in the left CgC. Whether this finding is adaptive or pathologic remains unclear. Significance: There is no evidence that 8-12 year old male football players sustain significant white matter changes after a single season of tackle football, although there is positive correlation of FA of the left cingulate gyrus to total magnitude of head impacts over the season.

scholarly journals Maximum Principal Strain and Strain Rate Associated with Concussion Diagnosis Correlates with Changes in Corpus Callosum White Matter Indices

2011 ◽  
Vol 40 (1) ◽  
pp. 127-140 ◽  
Author(s):  
Thomas W. McAllister ◽  
James C. Ford ◽  
Songbai Ji ◽  
Jonathan G. Beckwith ◽  
Laura A. Flashman ◽  
...  
Keyword(s):  
White Matter ◽  
Corpus Callosum ◽  
Strain Rate ◽  
Principal Strain ◽  
Maximum Principal Strain ◽  
Strain And Strain Rate

The effects of strain and strain rate on residual microstructures in copper

1986 ◽  
Vol 44 ◽  
pp. 420-421
Author(s):  
M. F. Stevens ◽  
P. S. Follansbee
Keyword(s):  
Strain Rate ◽  
Applied Stress ◽  
Threshold Stress ◽  
Rate Sensitivity ◽  
Viscous Drag ◽  
Strain Rates ◽  
Strain And Strain Rate ◽  
Threshold Strength ◽  
Mechanism Transition ◽  
Intrinsic Strength

The strain rate sensitivity of a variety of materials is known to increase rapidly at strain rates exceeding ∼103 sec-1. This transition has most often in the past been attributed to a transition from thermally activated guide to viscous drag control. An important condition for imposition of dislocation drag effects is that the applied stress, σ, must be on the order of or greater than the threshold stress, which is the flow stress at OK. From Fig. 1, it can be seen for OFE Cu that the ratio of the applied stress to threshold stress remains constant even at strain rates as high as 104 sec-1 suggesting that there is not a mechanism transition but that the intrinsic strength is increasing, since the threshold strength is a mechanical measure of intrinsic strength. These measurements were made at constant strain levels of 0.2, wnich is not a guarantee of constant microstructure. The increase in threshold stress at higher strain rates is a strong indication that the microstructural evolution is a function of strain rate and that the dependence becomes stronger at high strain rates.

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