MEA Forensic Engineers and Scientists

Richmond, Canada

MEA Forensic Engineers and Scientists

Richmond, Canada

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Curatolo M.,University of Bern | Bogduk N.,University of Newcastle | Ivancic P.C.,Yale University | McLean S.A.,University of North Carolina at Chapel Hill | And 3 more authors.
Spine | Year: 2011

Study Design. Nonsystematic review of cervical spine lesions in whiplash-associated disorders (WAD).Objective. To describe whiplash injury models in terms of basic and clinical science, to summarize what can and cannot be explained by injury models, and to highlight future research areas to better understand the role of tissue damage in WAD.Summary of Background Data. The frequent lack of detectable tissue damage has raised questions about whether tissue damage is necessary for WAD and what role it plays in the clinical context of WAD.Methods. Nonsystematic review.Results. Lesions of various tissues have been documented by numerous investigations conducted in animals, cadavers, healthy volunteers, and patients. Most lesions are undetected by imaging techniques. For zygapophysial (facet) joints, lesions have been predicted by bioengineering studies and validated through animal studies; for zygapophysial joint pain, a valid diagnostic test and a proven treatment are available. Lesions of dorsal root ganglia, discs, ligaments, muscles, and vertebral artery have been documented in biomechanical and autopsy studies, but no valid diagnostic test is available to assess their clinical relevance. The proportion of WAD patients in whom a persistent lesion is the major determinant of ongoing symptoms is unknown. Psychosocial factors, stress reactions, and generalized hyperalgesia have also been shown to predict WAD outcomes.Conclusion. There is evidence supporting a lesion-based model in WAD. Lack of macroscopically identifiable tissue damage does not rule out the presence of painful lesions. The best available evidence concerns zygapophysial joint pain. The clinical relevance of other lesions needs to be addressed by future research. © 2011, Lippincott Williams & Wilkins.


Zheng L.,Washington State University | Siegmund G.,MEA Forensic Engineers and Scientists | Siegmund G.,University of British Columbia | Ozyigit G.,Washington State University | And 2 more authors.
Journal of Biomechanics | Year: 2013

Biomechanical analyses of the head and neck system require knowledge of neck muscle forces, which are often estimated from neck muscle volumes. Here we use magnetic resonance images (MRIs) of 17 subjects (6 females, 11 males) to develop a method to predict the volumes of 16 neck muscles by first predicting the total neck muscle volume (TMV) from subject sex and anthropometry, and then predicting individual neck muscle volumes using fixed volume proportions for each neck muscle. We hypothesized that the regression equations for total muscle volume as well as individual muscle volume proportions would be sex specific. We found that females have 59% lower TMV compared to males (females: 510±43cm3, males: 814±64cm3; p<0.0001) and that TMV (in cm3) was best predicted by a regression equation that included sex (male=0, female=1) and neck circumference (NC, in cm): TMV=269+13.7NC-233Sex (adjusted R2=0.868; p<0.01). Individual muscle volume proportions were not sex specific for most neck muscles, although small sex differences existed for three neck muscles (obliqus capitis inferior, longus capitis, and sternocleidomastoid). When predicting individual muscle volumes in subjects not used to develop the model, coefficients of concordance ranged from 0.91 to 0.99. This method of predicting individual neck muscle volumes has the advantage of using only one sex-specific regression equation and one set of sex-specific volume proportions. These data can be used in biomechanical models to estimate muscle forces and tissue loads in the cervical spine. © 2013.


Powers C.M.,University of Southern California | Blanchette M.G.,University of Southern California | Brault J.R.,Semper Scientific | Flynn J.,J2 Engineering Inc. | Siegmund G.P.,MEA Forensic Engineers and Scientists
Journal of Forensic Sciences | Year: 2010

Tribometers are mechanical devices used to measure walkway coefficient of friction (COF) for the purpose of assessing slip risk. The purpose of this study was to define a tribometer reference standard and use it to assess the performance of various tribometers. Eighty subjects were randomly assigned to walk across one of four wet walkway surfaces (polished black granite, porcelain, vinyl composition tile, and ceramic tile) to establish the relative slipperiness of each surface. Eleven tribometers were subsequently used to measure and rank the COF of all four surfaces. Our results revealed that only four of the 11 tribometers (Wessex pendulum, Sigler pendulum, Mark II, and Mark III) met our compliance criteria by both correctly ranking all four surfaces and differentiating between surfaces of varying degrees of slipperiness. Our protocol demonstrates that human gait-based measures of slipperiness can be used to create reference standards against which tribometer measurements can be validated. © 2010 American Academy of Forensic Sciences.


Schmidt J.D.,University of Georgia | Guskiewicz K.M.,University of North Carolina at Chapel Hill | Blackburn J.T.,University of North Carolina at Chapel Hill | Mihalik J.P.,University of North Carolina at Chapel Hill | And 4 more authors.
American Journal of Sports Medicine | Year: 2014

Background: An athlete is thought to reduce head acceleration after impact by contracting the cervical musculature, which increases the effective mass of the head. Purpose: To compare the odds of sustaining higher magnitude in-season head impacts between athletes with higher and lower preseason performance on cervical muscle characteristics. Study Design: Cohort study; Level of evidence, 2. Methods: Forty-nine high school and collegiate American football players completed a preseason cervical testing protocol that included measures of cervical isometric strength, muscle size, and response to cervical perturbation. Head impact biomechanics were captured for each player using the Head Impact Telemetry System. A median split was used to categorize players as either high or low performers for each of the following outcome measures: isometric strength (peak torque, rate of torque development), muscle size (cross-sectional area), and response to cervical perturbation (stiffness, angular displacement, muscle onset latency). The odds of sustaining moderate and severe head impacts were computed against the reference odds of sustaining mild head impacts across cervical characteristic categorizations. Results: Linemen with stronger lateral flexors and composite cervical strength had about 1.75 times' increased odds of sustaining moderate linear head impacts rather than mild impacts compared with weaker linemen. Players who developed extensor torque more quickly had 2 times the increased odds of sustaining severe linear head impacts (odds ratio [OR], 2.10; 95% CI, 1.08- 4.05) rather than mild head impacts. However, players with greater cervical stiffness had reduced odds of sustaining both moderate (OR, 0.77; 95% CI, 0.61-0.96) and severe (OR, 0.64; 95% CI, 0.46-0.89) head impacts compared with players with less cervical stiffness. Conclusion: The study findings showed that greater cervical stiffness and less angular displacement after perturbation reduced the odds of sustaining higher magnitude head impacts; however, the findings did not show that players with stronger and larger neck muscles mitigate head impact severity. © 2014 The Author(s).


DeMarco A.L.,MEA Forensic Engineers and Scientists | Chimich D.D.,MEA Forensic Engineers and Scientists | Gardiner J.C.,MEA Forensic Engineers and Scientists | Nightingale R.W.,Duke University | And 2 more authors.
Accident Analysis and Prevention | Year: 2010

Helmets reduce the frequency and severity of head and brain injuries over a range of impact severities broader than those covered by the impact attenuation standards. Our goal was to document the impact attenuation performance of common helmet types over a wide range of impact speeds. Sixty-five drop tests were performed against the side of 10 different helmets onto a flat anvil at impact speeds of 0.9-10.1 m/s (energy-2-260J; equivalent drop heights of 0.04-5.2m). Three non-approved beanie helmets performed poorly, with the worst helmet reaching a peak headform acceleration of 852g at 29J. Three full-face and one open-face helmet responded similarly from about 100g at 30J to between 292g and 344g at 256-260J. Three shorty style helmets responded like the full-face helmets up to 150J, above which varying degrees of foam densification appeared to occur. Impact restitution values varied from 0.19 to 0.46. A three-parameter model successfully captured the plateau and densification responses exhibited by the various helmets (R2 =0.95-0.99). Helmet responses varied with foam thickness, foam material and possibly shell material, with the largest response differences consistent with either the presence/absence of a foam liner or the densification of the foam liner. © 2010 Elsevier Ltd. All rights reserved.


Siegmund G.P.,MEA Forensic Engineers and Scientists
Spine | Year: 2011

Study Design. Literature-based review.Objective. To review the published data on occupant kinematic and neuromuscular responses during low-speed impacts and analyze how these data inform our understanding of whiplash injury.Summary of Background Data. A stereotypical kinematic and neuromuscular response has been observed in human subjects exposed to rear-end impacts. Combined with various models of injury, these response data have been used to develop anti-whiplash seats that prevent whiplash injury in many, but not all, individuals exposed to a rear-end crash.Methods. Synthesis of the literature.Results. Understanding of the occupant kinematics and neuromuscular responses, combined with data from various seatrelated interventions, have shown that differential motion between the superior and inferior ends of the cervical spine is responsible for many whiplash injuries. The number of whiplash injuries not prevented by current anti-whiplash seats suggests than further work remains, possibly related to designing seats that respond dynamically to the occupant and collision properties. Neck muscles alter the head and neck kinematics during the interval in which injury likely occurs, even in initially relaxed occupants. It remains unclear whether muscle activation mitigates or exacerbates whiplash injury. If muscle activation mitigates injury, then advance warning could be used to help occupant tense their muscles before impact. Alternatively, if muscle activation exacerbates whiplash injury, then a loud preimpact sound that uncouples the startle and postural components of the muscle response could reduce peak muscle activation during a whiplash exposure.Conclusion. Our improved understanding of whiplash injury has led to anti-whiplash seats that have prevented many whiplash injuries. Further work remains to optimize these and possibly other systems to further reduce the number of whiplash injuries. © 2011, Lippincott Williams & Wilkins.


Carlsson A.,Chalmers University of Technology | Siegmund G.P.,MEA Forensic Engineers and Scientists | Linder A.,Swedish Road and Transport Research Institute | Svensson M.Y.,Chalmers University of Technology
Traffic Injury Prevention | Year: 2012

Objectives: The objectives of this study were to quantify and compare dynamic motion responses between 50th percentile female and male volunteers in rear impact tests. These data are fundamental for developing future occupant models for crash safety development and assessment.Methods: High-speed video data from a rear impact test series with 21 male and 21 female volunteers at 4 and 8 km/h, originally presented in Siegmund et al. (1997), were used for further analysis. Data from a subset of female volunteers, 12 at 4 km/h and 9 at 8 km/h, were extracted from the original data set to represent the 50th percentile female. Their average height was 163 cm and their average weight was 62 kg. Among the male volunteers, 11 were selected, with an average height of 175 cm and an average weight of 73 kg, to represent the 50th percentile male. Response corridors were generated for the horizontal and angular displacements of the head, T1 (first thoracic vertebra), and the head relative to T1. T-tests were performed with the statistical significance level of.05 to quantify the significance of the differences in parameter values for the males and females.Results: Several differences were found in the average motion response of the male and female volunteers at 4 and 8 km/h. Generally, females had smaller rearward horizontal and angular motions of the head and T1 compared to the males. This was mainly due to shorter initial head-to-head restraint distance and earlier head-to-head restraint contact for the females. At 8 km/h, the female volunteers showed 12 percent lower horizontal peak rearward head displacement (P =.018); 22 percent lower horizontal peak rearward head relative to T1 displacement (P =.018); and 30 percent lower peak head extension angle (P =.001). The females also had more pronounced rebound motion.Conclusions: This study indicates that there may be characteristic differences in the head-neck motion response between 50th percentile males and females in rear impacts. The exclusive use of 50th percentile male rear impact dummies may thus limit the assessment and development of whiplash prevention systems that adequately protect both male and female occupants. The results of this study could be used in the development and evaluation of a mechanical and/or computational average-sized female dummy model for rear impact safety assessment. These models are used in the development and evaluation of protective systems. It would be of interest to make further studies into seat configurations featuring a greater head-to-head restraint distance. © 2012 Copyright Taylor and Francis Group, LLC.


Young C.R.,MEA Forensic Engineers and Scientists | King D.J.,MEA Forensic Engineers and Scientists | Bertoch J.V.,MEA Forensic Engineers and Scientists
SAE Technical Papers | Year: 2016

The purpose of this study was to characterize the kinematics of four Chevrolet Tracker rollover tests and to determine their average and intermediate deceleration rates while traveling on concrete and dirt. Single vehicle rollover tests were performed using four 2001 Chevrolet Trackers fitted with six degree of freedom kinematic sensors. Tests were conducted using a rollover test device (RTD) in accordance with SAE J2114. The test dolly was modified (resting height of the vehicle wheels was raised) between tests 1, 2, and 3. The RTD was accelerated to 15.6 m/s (35 mph) and then decelerated rapidly by an energy absorbing crash cushion (EA) to cause the vehicle to launch and roll. The vehicles initially rolled on a smooth concrete surface and continued into loose dirt. This paper adds to the body of work identifying phases of constant deceleration during staged RTD tests and compares these phases to the overall deceleration rate. Across all tests, the average deceleration rate from launch to rest was 0.32g (range 0.31g to 0.36g). On concrete, the average deceleration rate was 0.23g (range 0.20g to 0.25g), and on dirt the average deceleration rate was 0.56g (range 0.37g to 0.66g). The dolly modifications minimized the interaction between the vehicle and the EA that caused vehicle 1 to yaw. These modifications changed the vehicle roll kinematics and initial roll rates, but did not affect the deceleration rates. © Copyright 2016 SAE International.


Turriff D.,MEA Forensic Engineers and Scientists | King D.J.,MEA Forensic Engineers and Scientists | Bertoch J.,MEA Forensic Engineers and Scientists
SAE Technical Papers | Year: 2015

Vehicle rollovers generate complicated damage patterns as a result of multiple vehicle-to-ground contacts. The goal of this work was to isolate and characterize specific directional features in coarse- and fine-scale scratch damage generated during a rollover crash. Four rollover tests were completed using stock 2001 Chevrolet Trackers. Vehicles were decelerated and launched from a rollover test device to initiate driver's side leading rolls onto concrete and dirt surfaces. Gross vehicle damage and both macroscopic and microscopic features of the scratch damage were documented using standard and macro lenses, a stereomicroscope, and a scanning electron microscope (SEM). The most evident indicators of scratch direction, and thus roll direction, were accumulations of abraded material found at the termination points of scratch-damaged areas. Abrasive wear mechanisms caused local plastic deformation patterns that were evident on painted sheet metal surfaces as well as plastic trim pieces. In both cases, abraded material is plowed towards and accumulates at the end of the scratches. Understanding the orientation and direction of scratches caused during rollover crashes can help to identify the direction of the rolls and potentially provide information regarding the number of rolls. Copyright © 2015 SAE International.


Heinrichs B.,MEA Forensic Engineers and Scientists | Mac Giolla Ri B.,MEA Forensic Engineers and Scientists | Hunter R.,MEA Forensic Engineers and Scientists
SAE International Journal of Passenger Cars - Mechanical Systems | Year: 2012

PC-Crash simulations of staged collisions require dozens of parameters describing vehicle and impact parameters. The Collision Optimizer will vary initial speeds and impact parameters to obtain a best fit to a desired end state, but vehicle parameters are left unchanged. The present paper allows these other parameters to vary in thousands of combinations, re-optimizing the solution in each to find the relationships between the previously fixed parameters and the resulting impact speeds. The results show that tire friction and vehicle inertial properties have the most influence on impact speeds. Other parameters have little influence on the results. © 2012 SAE International.

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