N km --A Proposal for a Neck Protection Criterion for Low-Speed Rear-End Impacts

Schmitt, Kai‐Uwe; Muser, Markus H.; Walz, Felix; Niederer, Peter F.

doi:10.1080/15389580212002

Cited by 60 publications

(18 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

Section: Differences In Head and Neck Morphologymentioning

confidence: 93%

“…In either of those cases, cervical spine loading and injury risk increase. 25,75,84,93 These findings highlight the importance of proper head restraint positioning to reduce risk of head-neck injury during automotive rear impacts.Viano 109 described another possible explanation for greater female susceptibility based on the energy-absorbing capacity of the seatback due to rearward deflection about the pivot point. As the vehicle is accelerated forward, the occupant's inertia pushes against the seatback, resulting in compression of the part, as an explanation.…”

mentioning

confidence: 93%

See 1 more Smart Citation

Whiplash-Associated Disorders: Occupant Kinematics and Neck Morphology

Stemper¹,

Corner²

2016

J Orthop Sports Phys Ther

View full text Add to dashboard Cite

FIGURE 1.Initial phases of head-neck response to automotive rear impacts. The rear impact initiates with the occupant in a neutral upright position. As the thorax is accelerated anteriorly, the head remains stationary during the retraction phase, producing an S-shaped cervical spine curvature. Eventually, loads from the thorax are transferred up the cervical spine and the head-neck complex transitions into extension, with the cervical spine in an overall C-shaped extension curvature. The head eventually rebounds forward (not shown), and the cervical spine then transitions into flexion. Used with permission from Stemper et al. 93 Copyright ©2011 Wiley-Liss, Inc. foam/springs and rearward deflection, which absorb energy and decrease impact severity for the occupant. The magnitude of seatback deformation and deflection is dependent on the occupant's torso mass and center of gravity. Greater mass and higher center of gravity contribute to greater deflection and decreased overall impact severity. Average female body mass is 20% lighter and torso height is 8% shorter. 30,31 Therefore, the ability to deflect the seatback is decreased in females, who would experience more severe loading on the head-neck complex during a given rear impact.This section highlighted the role of body size on cervical spine injury risk during automotive rear impacts, advancing the theory that size-based mismatches between the vehicle seat and occupant anthropometrics contribute to greater injury risk for smaller occupants. This concept would hold true for either males or females, but may help explain the preponderance of whiplash injuries in females due to their generally smaller body size. Shorter sitting height can result in head interaction with the bottom of the head restraint, which increases injury risk. However, taller occupants with incorrectly adjusted head restraints also experience increased injury risk due to the head rotating over the head restraint and increasing extension moments on the cervical spine. Decreased body mass and shorter center-of-torso mass in smaller occupants also contribute to decreased dynamic energy absorption of the seatback. While these differences illustrate mechanisms of increased injury risk for smaller occupants, other morphological differences may also contribute. Differences in Head and Neck MorphologyGiven that a majority of injuries resulting from automotive rear impacts affect the cervical spine, 9 differences in headneck morphology can influence injury risk. Once again, sex-based differences will be used to demonstrate this concept. Neck slenderness, a mechanical term body sizes farther from those standards may not be protected as well.Research studies report that head-tohead restraint backset is lower in females than in males due to rearward incline of automotive seats and decreased sitting height for average females compared to males.12 Sitting height for average females is approximately 6 cm shorter than that for average males. 30,31 This means that the posterior aspect of the head for the comp...

show abstract

Section: Differences In Head and Neck Morphologymentioning

confidence: 93%

mentioning

confidence: 93%

Whiplash-Associated Disorders: Occupant Kinematics and Neck Morphology

Stemper¹,

Corner²

2016

J Orthop Sports Phys Ther

View full text Add to dashboard Cite

show abstract

“…Neck surrogates of modern day anthropometric test dummies, such as the Hybrid III and BioRID II, are routinely utilized to simulate dynamic cervical spine trauma, although they incorporate quasi-static physical properties (Schmitt et al, 2002). The same is true for cervical spine models for dynamic loading simulation (de Jager et al, 1996;van der Horst, 2002).…”

Section: Discussionmentioning

confidence: 98%

“…Neck injury prevention systems, such as the vehicle interior, automobile seat, head restraint, air bag, and air curtain, are commonly evaluated via crash testing of anthropometric test dummies or using mathematical models of the cervical spine (Eriksson, 2004;Schmitt et al, 2002;van der Horst, 2002;Zuby et al, 1999). Neck surrogates of the present day dummies, such as the Hybrid III or BioRID II, have been developed without prerequisite knowledge of the dynamic flexibility coefficients at each spinal level of the human neck.…”

Section: Introductionmentioning

confidence: 99%

Dynamic sagittal flexibility coefficients of the human cervical spine

Ivancic¹,

Ito²,

Panjabi³

2007

Accident Analysis & Prevention

View full text Add to dashboard Cite

“…It is based on the hypothesis that transient pressure changes in the cervical spinal canal, caused by a quick extension/flexion motion of the neck, lead to ganglion injuries. The N km value is based on the summation of normalised shear loads in the AP direction and flexion/extension moments, similar to the N ij (Schmitt et al 2002). The critical intercepts used to normalise the load and moment were based on noninjurious volunteer studies (Mertz and Patrick 1971;Goldsmith and Ommaya 1984).…”

Section: Neck Injury Biomechanics and Tolerancesmentioning

confidence: 99%

Cross-sectional neck response of a total human body FE model during simulated frontal and side automobile impacts

White

Moreno

Gayzik

et al. 2013

Computer Methods in Biomechanics and Biomedical Engineering

View full text Add to dashboard Cite

Human body finite element (FE) models are beginning to play a more prevalent role in the advancement of automotive safety. A methodology has been developed to evaluate neck response at multiple levels in a human body FE model during simulated automotive impacts. Three different impact scenarios were simulated: a frontal impact of a belted driver with airbag deployment, a frontal impact of a belted passenger without airbag deployment and an unbelted side impact sled test. Cross sections were created at each vertebral level of the cervical spine to calculate the force and moment contributions of different anatomical components of the neck. Adjacent level axial force ratios varied between 0.74 and 1.11 and adjacent level bending moment ratios between 0.55 and 1.15. The present technique is ideal for comparing neck forces and moments to existing injury threshold values, calculating injury criteria and for better understanding the biomechanical mechanisms of neck injury and load sharing during sub-injurious and injurious loading.

show abstract

N km --A Proposal for a Neck Protection Criterion for Low-Speed Rear-End Impacts

Cited by 60 publications

References 15 publications

Whiplash-Associated Disorders: Occupant Kinematics and Neck Morphology

Whiplash-Associated Disorders: Occupant Kinematics and Neck Morphology

Dynamic sagittal flexibility coefficients of the human cervical spine

Cross-sectional neck response of a total human body FE model during simulated frontal and side automobile impacts

Contact Info

Product

Resources

About