The relationship between lower neck shear force and facet joint kinematics during automotive rear impacts

Stemper, Brian D.; Yoganandan, Narayan; Pintar, Frank A.; Maiman, Dennis J.

doi:10.1002/ca.21172

Cited by 8 publications

(9 citation statements)

References 46 publications

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Section: Differences In Head and Neck Morphologymentioning

confidence: 92%

“…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.…”

Section: Figurementioning

confidence: 99%

“…The headneck complex sustains inertial loading during the initial stages of a rear impact (FIGURE 1). 18,21,27,34,49,51,90,93,103,114 In this type of loading, the structural response of the cervical spine is dependent on the input acceleration pulse applied at the cervicothoracic junction 84,96,114 and on the interaction of the head and spinal components. In response to a typical rear-end collision, the cervical spine undergoes 3 distinct kinematic phases: S-curvature resulting from the head lagging behind the thorax (ie, retraction), 66,67,90 C-curvature characterized by head-neck extension, and rebound of the head from the head restraint.…”

Section: Occupant Kinematics During Rear Impactmentioning

confidence: 99%

“…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: 92%

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Whiplash-Associated Disorders: Occupant Kinematics and Neck Morphology

Stemper¹,

Corner²

2016

J Orthop Sports Phys Ther

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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...

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Section: Differences In Head and Neck Morphologymentioning

confidence: 92%

Section: Figurementioning

confidence: 99%

Section: Occupant Kinematics During Rear Impactmentioning

confidence: 99%

mentioning

confidence: 92%

See 2 more Smart Citations

Whiplash-Associated Disorders: Occupant Kinematics and Neck Morphology

Stemper¹,

Corner²

2016

J Orthop Sports Phys Ther

Self Cite

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“…Lateral X‐rays were obtained following each test and compared to pre‐test X‐rays to identify bony fracture, or notable changes in spinal alignment or intervertebral disc heights. If X‐ray images did not reveal bony injury, specimen palpation at each spinal level and flexion stiffness assessments described previously were used to identify the presence of laxity that was indicative of endplate or soft tissue injury. A clinical member of our team participated in the assessment of pre‐ and post‐test X‐ray images, as well as specimen palpations.…”

Section: Methodsmentioning

confidence: 99%

Biomechanical tolerance of whole lumbar spines in straightened posture subjected to axial acceleration

Stemper

Chirvi

Doan

et al. 2017

Journal Orthopaedic Research

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Quantification of biomechanical tolerance is necessary for injury prediction and protection of vehicular occupants. This study experimentally quantified lumbar spine axial tolerance during accelerative environments simulating a variety of military and civilian scenarios. Intact human lumbar spines (T12-L5) were dynamically loaded using a custom-built drop tower. Twenty-three specimens were tested at sub-failure and failure levels consisting of peak axial forces between 2.6 and 7.9 kN and corresponding peak accelerations between 7 and 57 g. Military aircraft ejection and helicopter crashes fall within these high axial acceleration ranges. Testing was stopped following injury detection. Both peak force and acceleration were significant (p < 0.0001) injury predictors. Injury probability curves using parametric survival analysis were created for peak acceleration and peak force. Fifty-percent probability of injury (95%CI) for force and acceleration were 4.5 (3.9-5.2 kN), and 16 (13-19 g). A majority of injuries affected the L1 spinal level. Peak axial forces and accelerations were greater for specimens that sustained multiple injuries or injuries at L2-L5 spinal levels. In general, force-based tolerance was consistent with previous shorter-segment lumbar spine testing (3-5 vertebrae), although studies incorporating isolated vertebral bodies reported higher tolerance attributable to a different injury mechanism involving structural failure of the cortical shell. This study identified novel outcomes with regard to injury patterns, wherein more violent exposures produced more injuries in the caudal lumbar spine. This caudal migration was likely attributable to increased injury tolerance at lower lumbar spinal levels and a faster inertial mass recruitment process for high rate load application. Published 2017. This article is a U.S. Government work and is in the public domain in the USA. J Orthop Res 36:1747-1756, 2018.

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Importance of the cervical capsular joint cartilage geometry on head and facet joint kinematics assessed in a Finite element neck model

Corrales

Cronin

2021

Journal of Biomechanics

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The relationship between lower neck shear force and facet joint kinematics during automotive rear impacts

Cited by 8 publications

References 46 publications

Whiplash-Associated Disorders: Occupant Kinematics and Neck Morphology

Whiplash-Associated Disorders: Occupant Kinematics and Neck Morphology

Biomechanical tolerance of whole lumbar spines in straightened posture subjected to axial acceleration

Importance of the cervical capsular joint cartilage geometry on head and facet joint kinematics assessed in a Finite element neck model

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