Name: a test bed to examine helmet fit and retention and biomechanical measures of head and neck injury in simulated impact
Uploaded: 2017-09-21T15:00:00
Description: Watch this Scientific Journal Video about A Test Bed to Examine Helmet Fit and Retention and Biomechanical Measures of Head and Neck Injury in Simulated Impact at JoVE.com

We gratefully acknowledge funding from the Natural Science and Engineering Research Council (NSERC) of Canada (Discovery Grants 435921), the Pashby Sport Safety Fund (2016: RES0028760), the Banting Research Foundation (Discovery Award 31214), NBEC Inc. (Canada), and the Faculty of Engineering and Department of Mechanical Engineering at the University of Alberta.

1. Helmet Fit Scenarios Arrangement
<ol>
	<li>Define fit scenarios to be studied on an anthropometric test device head and neck (Hybrid III 50th percentile male) with a head circumference of 575 mm. 
	NOTE: An example of four fit scenarios is shown in Table 1 with helmet positions corresponding to Figure 1. The forward and backward fit scenarios were based on definitions of correct helmet use from previous epidemiological studies, which specified proper helmet positio...

<ol>
	<li>Thompson, D. C., Rivara, F. P., Thompson, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effectiveness+of+Bicycle+Safety+Helmets+in+Preventing+Head+Injuries:+A+Case-Control+Study.">Effectiveness of Bicycle Safety Helmets in Preventing Head Injuries: A Case-Control Study.</a> JAMA. 276 (24), 1968-1973 (1996).</li><li>Cripton, P. A., Dressler, D. M., Stuart, C. A., Dennison, C. R., Richards, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bicycle+helmets+are+highly+effective+at+preventing+head+injury+during+head+impact:+Head-form+accelerations+and+injury+criteria+for+helmeted+and+unhelmeted+impacts.">Bicycle helmets are highly effective at preventing head injury during head impact: Head-form accelerations and injury criteria for helmeted and unhelmeted impacts.</a> Accid. Anal. Prev. 70, 1-7 (2014).</li><li>Lee, R. S., Hagel, B. E., Karkhaneh, M., Rowe, B. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+systematic+review+of+correct+bicycle+helmet+use:+how+varying+definitions+and+study+quality+influence+the+results.">A systematic review of correct bicycle helmet use: how varying definitions and study quality influence the results.</a> Inj. Prev. 15 (2), 125-131 (2009).</li><li>Chang, L. -. T., Chang, C. -. H., Chang, G. -. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fit+effect+of+motorcycle+helmet+-+A+finite+element+modeling.">Fit effect of motorcycle helmet - A finite element modeling.</a> JSME Int. J. Ser. Solid Mech. Mater. Eng. 44 (1), 185-192 (2001).</li><li>Testing of Bicycle Helmets for Preadolescents. IRCOBI Conf. Proc Available from: <a target="_blank" href="https://trid.trb.org/view.aspx?id=1370437">https://trid.trb.org/view.aspx?id=1370437</a> (2015)</li><li>McIntosh, A. S., Lai, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Motorcycle+Helmets:+Head+and+Neck+Dynamics+in+Helmeted+and+Unhelmeted+Oblique+Impacts.">Motorcycle Helmets: Head and Neck Dynamics in Helmeted and Unhelmeted Oblique Impacts.</a> Traffic Inj. Prev. 14 (8), 835-844 (2013).</li><li>Olivier, J., Creighton, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bicycle+injuries+and+helmet+use:+a+systematic+review+and+meta-analysis.">Bicycle injuries and helmet use: a systematic review and meta-analysis.</a> Int. J. Epidemiol. 46 (1), 278-292 (2017).</li><li>Rivara, F. P., Thompson, D. C., Thompson, R. 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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+external+helmet+accessories+on+biomechanical+measures+of+head+injury+risk:+An+ATD+study+using+the+HYBRIDIII+headform.">Effects of external helmet accessories on biomechanical measures of head injury risk: An ATD study using the HYBRIDIII headform.</a> J. Biomech. 48 (14), 3816-3824 (2015).</li><li>Dennison, C. R., Wild, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Superstructured+fiber-optic+contact+force+sensor+with+minimal+cosensitivity+to+temperature+and+axial+strain.">Superstructured fiber-optic contact force sensor with minimal cosensitivity to temperature and axial strain.</a> Appl. Opt. 51, 1188-1197 (2012).</li><li>Dennison, C. R., Wild, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sensitivity+of+Bragg+gratings+in+birefringent+optical+fibre+to+transverse+compression+between+conforming+materials.">Sensitivity of Bragg gratings in birefringent optical fibre to transverse compression between conforming materials.</a> Appl. Opt. 49, 2250-2261 (2010).</li><li>Knowles, B. M., Yu, H., Dennison, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+a+Wearable+Sensor+for+Measures+of+Head+Kinematics+and+Calculation+of+Brain+Tissue+Strain.">Accuracy of a Wearable Sensor for Measures of Head Kinematics and Calculation of Brain Tissue Strain.</a> J. Appl. Biomech. 33 (1), 2-11 (2017).</li><li>Nightingale, R. W., McElhaney, J. H., Richardson, W. J., Myers, B. 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Mech. 42 (3), 552-556 (1975).</li><li>SAE. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> J211 Instrumentation for Impact Test - Part 1: Electronic Instrumentation. , (2014).</li><li>Depreitere, B., Lierde, C. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bicycle-related+head+injury:+a+study+of+86+cases.">Bicycle-related head injury: a study of 86 cases.</a> Accid. Anal. Prev. 36, 561-567 (2004).</li><li>Influence of Impact Velocity and Angle in a Detailed Reconstruction of a Bicycle Accident. Proc. 2012 Int. IRCOBI Conf. Biomech. Impacts Available from: <a target="_blank" href="https://lirias.kuleuven.be/handle/123456789/357473">https://lirias.kuleuven.be/handle/123456789/357473</a> (2012)</li><li>Newman, J. 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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+comparison+of+Hybrid+III+and+National+Operating+Committee+on+Standards+for+Athletic+Equipment+headform+shape+characteristics+and+implications+on+football+helmet+fit.">Quantitative comparison of Hybrid III and National Operating Committee on Standards for Athletic Equipment headform shape characteristics and implications on football helmet fit.</a> Proc. Inst. Mech. Eng. Part P J. Sports Eng. Technol. 229 (1), 39-46 (2015).</li><li>Cobb, B. R., Zadnik, A. 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Here, methods for investigating helmet fit in simulated helmeted head impacts are presented. Helmet fit was quantified with fit force sensors, impacts were simulated with an ATD headform and neck on a guided drop tower, and helmet movement was tracked with high speed video. Different impact scenarios were simulated under different fit scenarios to investigate the effects on biomechanical measures of helmet fit.
The helmet fit sensors are capable of distinguishing differences in fit forces betw...

Most epidemiological evidence suggests bicycle helmets provide protection against head injuries for cyclists of all ages1. The biomechanical literature presents the consistent theme that the helmeted head sustains relatively less severe head/brain injuries secondary to impact, relative to the unprotected (un-helmeted) head2. Some research suggests that poor helmet fit is associated with an increased risk of head injury3, implying that helmets are most effective when fit properly. Depending on the criteria used to define good helmet fit, incorrect helmet use was found to be as high as 64% among helmeted cyclists3. Despite epidemiological evidence suggesting that helmet fit is relevant in the severity or likelihood of head injury in an impact, there is minimal experimental work assessing in a controlled laboratory setting whether or not correct helmet fit or helmet retention has a significant effect on biomechanical measures of injury. One related study investigates the effect of motorcycle helmet sizing during helmeted impacts simulated with a finite element model4. Another related study investigates the effect of helmet sizing during experimental impacts5 while using pressure sensitive film to quantify fit forces in football helmets. The effect of retention systems in bicycle and motorcycle helmet impacts have been investigated6,7, as well as a backward fit scenario for preadolescents6.
Our work proposes methods to study the effect of bicycle helmet fit on the risk of injury with helmet fit force sensors, simulated impacts with an anthropometric head and neck, and stereoscopic high-speed cameras. The goals of our proposed methods are to quantify fit and evaluate the risk of injury in different realistic impact scenarios. In contrast to related methods, our work investigates bicycle helmet fit, where proper helmet use is varied. Similar to previous methods, head kinematics are determined; however, neck loading and head-helmet displacements are also quantified. Although the epidemiology of neck injury in cycling suggests that neck injuries are uncommon, they tend to be associated with more severe head impacts and hospitalization8,9. The evidence is mixed on whether or not helmet use reduces rates of neck injury8 and none of the cited epidemiological studies quantify aspects of helmet fit. Considering the fact that neck injury in cycling tends to be associated with more severe accidents and that helmet fit has not been examined in neck injury epidemiology, methods for examining both head and neck injury are valuable in biomechanical research. Such experimental methods could be used in biomechanical studies that complement epidemiological studies which cannot in all cases control for impact severity or helmet fit.
In our work, a novel method of monitoring relative motions between the head and helmet during impact has been developed. The ability to monitor whether or not the helmet moves on the head can give valuable insight into both helmet stability and exposure of the unprotected head to injury during impact. In a study investigating helmet fit, helmet stability and head exposure are particularly valuable in evaluating helmet performance. In contrast to related work, different impact and fit scenarios emphasizing varied helmet positioning will also be tested.
Currently, correct helmet fit is subjective and nonspecifically defined. Generally, good helmet fit is characterized by stability and position. The helmet should be resistant to movement once secured on the head, and should be positioned such that the eyebrows are not covered and the forehead is not excessively exposed. Furthermore, approximately one-finger width of space should fit between the chin and chinstrap3. Measures of quantifying helmet fit are not widespread; other than force, methods may compare helmet fit based on comparing head and helmet geometry. One such method is the Helmet Fit Index proposed by Ellena et al.10. Our proposed method of quantifying helmet fit, fit force sensors, creates an objective means of comparing different helmet fit scenarios in the form of average and standard deviation of forces exerted on the head. These fit force values represent the tightness of a helmet, as well as the variation of tightness experienced on the head. These sensors provide a quantified comparison of forces that can be made between different fit scenarios. A secure tight fitting helmet would show higher forces while a loose helmet would show lower forces. This method of fit force measurement is similar to the Average Fit Index proposed by Jadischke5. However, Jadischke&#39;s methods utilize pressure sensitive film. The optical sensors we present allow unobtrusive measurement of fit force around the head or helmet.
For certification of helmets, a helmet is secured on an instrumented headform, which is then raised to a certain height to be dropped. The head and helmet is then subject to a free fall drop onto an anvil while recording linear accelerations. Although not typically used in helmet industry standards, a Hybrid III head (headform) and neck assembly were used in this work, with a guided drop tower to simulate impacts. In contrast to standards that typically use linear kinematics, the headform accelerometer array also allows the determination of rotational kinematics, a key parameter in predicting the likelihood of diffuse brain injuries, including concussion11. Through measurement of both linear acceleration and rotational acceleration and velocity, estimates of severe focal and diffuse head injury can be made by comparing kinematics to the several proposed kinematics-based injury assessment methods in the literature12,13. While the headform was originally developed for automotive crash testing, its use in helmet assessment and estimation of head injury risk in helmeted impact is well documented2,14. The impact simulation setup also includes an upper neck load cell, allowing the forces and moments associated with neck injury to be measured. Neck injury risk can then be estimated by comparing neck kinetics to injury assessment data from automotive injury data12,13.
A method of tracking helmet movement relative to the head during impact with high speed video is also proposed. Currently, no quantitative methods exist to evaluate helmet stability during impact. The Consumer Product Safety Commission (CPSC)15 bicycle helmet standard calls for a positional stability test, but is not representative of an impact. Furthermore, whether or not the helmet comes off the headform is the only result measured by the test. Regardless of exposure of the head to injury, a helmet may still pass as long as it stays on the headform during tests. The proposed method of tracking helmet movement is similar to Helmet Position Index (HPI)15 and measures the distance between the brim of a helmet and the forehead. This head-helmet displacement is tracked using high-speed video footage throughout an impact in order to obtain a representation of helmet stability and head exposure during impact. Using Direct Linear Transform (DLT)16 and Single Value Decomposition (SVD)17 methods, markers are tracked from two cameras to determine point locations in three-dimensional space and then the relative displacement between helmet and head.
Several impact severity and fit parameters are investigated. The impact scenarios include two impact speeds, two impacting anvil surfaces, and both torso-first and head-first impacts. In addition to a typical flat anvil surface, an angled anvil impact is also simulated to induce a tangential force component. A torso-first impact, as opposed to a head-first impact, is included to simulate a scenario in which a rider&#39;s shoulder impacts the ground before the head, similarly performed in previous work18. Finally, these four helmet fit scenarios are investigated: a regular fit, an oversized fit, a forward fit, and a backward fit. Unlike previous work, helmet positioning on the head is an investigated parameter, as well as helmet fit and helmet sizing.

<table>
	<tbody>
		<tr>
			<td>Hybrid III Headform</td>
			<td>Humanetics/Jasti-Utama</td>
			<td>N/A</td>
			<td>50th Percentile ATD, for impact simulation</td>
		</tr>
		<tr>
			<td>Hybrid III Neck</td>
			<td>Humanetics/Jasti-Utama</td>
			<td>N/A</td>
			<td>50th Percentile ATD, for impact simulation</td>
		</tr>
		<tr>
			<td>Linear Accelerometers</td>
			<td>Measurement Specialties</td>
			<td>64C-2000-360</td>
			<td>for head acceleration measurement</td>
		</tr>
		<tr>
			<td>Upper Neck Load Cell</td>
			<td>mg Sensor</td>
			<td>N6ALB11A</td>
			<td>for neck load measurement</td>
		</tr>
		<tr>
			<td>High Speed Camera</td>
			<td>Vision Research</td>
			<td>v611</td>
			<td>for motion capture</td>
		</tr>
		<tr>
			<td>Camera Lens</td>
			<td>Carl Zeiss</td>
			<td>N/A</td>
			<td>50 mm f1/.4, for motion capture</td>
		</tr>
		<tr>
			<td>Camera Lens</td>
			<td>Carl Zeiss</td>
			<td>N/A</td>
			<td>100 mm f/2.0, for motion capture</td>
		</tr>
		<tr>
			<td>Bicycle Helmet</td>
			<td>Bell</td>
			<td>N/A</td>
			<td>Traverse</td>
		</tr>
		<tr>
			<td>Data Acquisition System</td>
			<td>National Instruments</td>
			<td>PXI 6251</td>
			<td>for Hybrid III signal acquisition</td>
		</tr>
		<tr>
			<td>Head Impact Drop Tower</td>
			<td>University of Alberta</td>
			<td>N/A</td>
			<td>Custom-designed, for impact simulation</td>
		</tr>
		<tr>
			<td>Optical Interrogator</td>
			<td>Smart Fibres Ltd.</td>
			<td>N/A</td>
			<td>SmartScan, for optical sensor force measurement</td>
		</tr>
		<tr>
			<td>Fit Force Sensor</td>
			<td>University of Alberta</td>
			<td>N/A</td>
			<td>Custom-designed, for measuring helmet fit forces</td>
		</tr>
	</tbody>
</table>

a test bed to examine helmet fit and retention and biomechanical measures of head and neck injury in simulated impact

Conventional wisdom and the language in international helmet testing and certification standards suggest that appropriate helmet fit and retention during an impact are important factors in protecting the helmet wearer from impact-induced injury. This manuscript aims to investigate impact-induced injury mechanisms in different helmet fit scenarios through analysis of simulated helmeted impacts with an anthropometric test device (ATD), an array of headform acceleration transducers and neck force/moment transducers, a dual high speed camera system, and helmet-fit force sensors developed in our research group based on Bragg gratings in optical fiber. To simulate impacts, an instrumented headform and flexible neck fall along a linear guide rail onto an anvil. The test bed allows simulation of head impact at speeds up to 8.3 m/s, onto impact surfaces that are both flat and angled. The headform is fit with a crash helmet and several fit scenarios can be simulated by making context specific adjustments to the helmet position index and/or helmet size. To quantify helmet retention, the movement of the helmet on the head is quantified using post-hoc image analysis. To quantify head and neck injury potential, biomechanical measures based on headform acceleration and neck force/moment are measured. These biomechanical measures, through comparison with established human tolerance curves, can estimate the risk of severe life threatening and/or mild diffuse brain injury and osteoligamentous neck injury. To our knowledge, the presented test-bed is the first developed specifically to assess biomechanical effects on head and neck injury relative to helmet fit and retention.

Fit Force Measurement 
For each fit scenario, fit force measurement was performed at each sensor location (Figure 12) and a t-test, assuming unequal variances, was performed to determine significance (p &#60; 0.05). The average standard deviation across all measurements was &#177; 0.14 N. Higher fit forces indicate a tighter fit.
Head Kinematic and Neck Kinetic Data</st...

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A Test Bed to Examine Helmet Fit and Retention and Biomechanical Measures of Head and Neck Injury in Simulated Impact

Using an anthropometric head and neck, optical fiber-based fit force transducers, an array of head acceleration and neck force/moment transducers, and a dual high speed camera system, we present a test bed to study helmet retention and effects on biomechanical measures of head and neck injury secondary to head impact.

Conventional wisdom and the language in international helmet testing and certification standards suggest that appropriate helmet fit and retention during ...

Research

JoVE Journal

Bioengineering

Creating Two-Dimensional Patterned Substrates for Protein and Cell Confinement

Microcontact printing provides a rapid, highly reproducible method for the creation of well-defined patterned substrates.1  While microcontact printing ...

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic ...

Directed Cellular Self-Assembly to Fabricate Cell-Derived Tissue Rings for Biomechanical Analysis and Tissue Engineering

Each year, hundreds of thousands of patients undergo coronary artery bypass surgery in the United States.1 Approximately one third of these patients do ...

Ferromagnetic Bare Metal Stent for Endothelial Cell Capture and Retention

Rapid endothelialization of cardiovascular stents is needed to reduce stent thrombosis and to avoid anti-platelet therapy which can reduce bleeding risk. ...

Training Persons with Spinal Cord Injury to Ambulate Using a Powered Exoskeleton

Powered exoskeletons have become available for overground ambulation in persons with paralyses due to spinal cord injury (SCI) who have intact upper ...

Biomechanical Characterization of Human Soft Tissues Using Indentation and Tensile Testing

Regenerative medicine aims to engineer materials to replace or restore damaged or diseased organs. The mechanical properties of such materials should ...

An Experimental and Finite Element Protocol to Investigate the Transport of Neutral and Charged Solutes across Articular Cartilage

Osteoarthritis (OA) is a debilitating disease that is associated with degeneration of articular cartilage and subchondral bone. Degeneration of articular ...

A Microfluidic Flow Chamber Model for Platelet Transfusion and Hemostasis Measures Platelet Deposition and Fibrin Formation in Real-time

Microfluidic models of hemostasis assess platelet function under conditions of hydrodynamic shear, but in the presence of anticoagulants, this analysis is ...

Retroductal Nanoparticle Injection to the Murine Submandibular Gland

Two common goals of salivary gland therapeutics are prevention and cure of tissue dysfunction following either autoimmune or radiation injury. By locally ...

Seeding and Implantation of a Biosynthetic Tissue-engineered Tracheal Graft in a Mouse Model

Treatment options for congenital or secondary long segment tracheal defects have historically been limited due to an inability to replace functional ...