Low Speed Rear-End Low Speed Rear-End CollisionsCollisions

Mechanism of Injury

www.InjuryResources.com

© Copyright 2002, BodyMind Publications.

Viano and Gargan documented the head restraint position of 1,915 vehicles at an intersection. They found that only 10% of the occupants had the head restraint in the proper position to avoid hyperextension. Only ¼ of the adjustable head restraints were in the “up” position.

• Viano DC, Gargan MF. Headrest position during normal driving: implication to neck injury risk in rear crashes. Accident Analysis and Prevention 1996;28(6):665-674.

Improper HeadRestraint Positioning

Proper HeadRestraint Positioning

1. Normal Position 2. Spine Straightens

3. Head Extension 4. Rebound

The Phases of a Rear-End Collision

• Car seat begins to move forward

• Occupant remains stationary, due to inertia

• No occupant forces

0 milliseconds

• Car seat pushes into occupants torso

• Torso is accelerated forward with the seat

• Head is still stationary, due to inertia

100 milliseconds

• Torso fully accelerated by the car seat

• Lower neck is pulled forward by the rapidly moving torso

• Causing the head to rotate backward over the head restraint

150 milliseconds

• Head is still moving backwards

• Car seat begins to spring forward

• Torso is again accelerated forward

175 milliseconds

• Head and torso are accelerated forward ahead of the car seat, resulting in flexion of the spine

300 milliseconds

Normal Cervical Spine

• Normal, smooth curvature of the spine

• Each intervertebral joint contributes evenly to the motion

Normal Cervical Spine Extension

Normal Flexion and Extension

Normal spinal motion results from small motions in each individual vertebral joint.

The normal motion of each joint is limited to just a few degrees of movement.

Click on image to start or pause video

0 millisecondsAt the moment of impact, the car seat just begins to move and the occupant has not yet been accelerated forward.

Motion During a Collision

Motion During a Collision

As the car seatback pushes the torso forward, the spine moves forward, resulting in a straightening of the thoracic and cervical spine.

Head remains stationary

Seatback pushes torso forward

50 milliseconds

Spine straightens

This difference in motion between the neck and torso results in an S-shaped curve, where nearly all of the bending in the cervical spine takes place in the lower cervical spine.

This rapid bending in just a few joints can result in ligament damage in the lower spine.

At this point in the collision, the car seat is rapidly pushing the occupant's torso forward, while the head remains stationary due to inertia.

Head remains stationary

Seatback pushes torso forward

75 millisecondsMotion During a Collision

Spine forms an abnormal

S-shape formation

75 milliseconds50 milliseconds

Spine Straightens S-Shaped Curve

Injury Causing Motion

At about 150 milliseconds, the torso has pulled so far forward on the lower neck that the head is forced backwards over the head restraint.

Depending on the severity of the collision, the ligaments in the front portion of the spine can be injured during this phase of the collision.

Head rotates back

Seatback pushes torso

forward

150 milliseconds

Motion During a Collision

Finally, the head and torso are thrown forward by the force of the car seat.

Head thrown forward

Force from car seat

200 milliseconds

Motion During a Collision

Ligaments of the Cervical Spine

Facet capsular ligaments

Vertebral BodyFacet Joints

Intervertebral DiscSpinous Process

Facets

Normal Gliding Motion

The Cervical Facet Joints

The Facet Joint

Facet joint

X-ray of facet joint.

The arrows show the normal gliding motion of these joints.

Normal Facet Motion

The cervical vertebrae are designed for smooth, even motion.

The facet joints stabilize the spine and allow this forward and backward movement.

Click on image to start or pause video

Animation of Abnormal Spinal Motion

During a low speed, rear-end collision, the movement of the head and neck is focused on just a few spinal segments.

This results in the s-shaped curve motion that can cause injury.

Click on image to start or pause video

Normal vs. Abnormal Motion

Normal Flexion/Extension:

Smooth, even motion of all spinal segments

Abnormal S-Shaped Curve:

Dramatic movement in just a few spinal segments

Click on image to start or pause video

Pinching of facet

Torso movement forward

Torso moving forward

Tearing of ligaments and disc

Facet Joint

Reflectors

Stretch of facet capsule

Abnormal Facet Motion

Vertebral Motion During Impact

Instead of a smooth motion, the cervical spine experiences simultaneous compression and shear.

This can cause tearing in the front portion of the spine and pinching in the facet joints.

Click on image to start or pause video

The rapid motion of the neck during a crash can result in a number of injuries - many of which are impossible to see on x-rays or MRI. Here are some of the injuries that have been shown after whiplash crashes.

1. Rim Lesions

2. Endplate avulsions

3. Tears of the anterior longitudinal ligament

4. Uncinate process

5. Articular subchondral fractures

6. Articular pillar

7. Articular process

8. Ligament Tear

Areas of Injury

The pain from inflamed facet joints is transmitted by the medial branch of the dorsal ramus. Stimulation of the facet nerves often results in referred pain.

Facet Joints

Medial Branch

Dorsal Ramus

Spinous Process

Spinal Cord

Nerves of the Facet Joint

"... the prevalence of cervical zygapophysial joint pain was 60%."

The most common facets to be injured were at C2/C3 and C5/C6.

Wallis BJ, Lord SM, Bogduk N. Resolution of psychological distress of whiplash patients following treatment by radiofrequency neurotomy: a randomised, double-blind, placebo-controlled trial. Pain 1997;73:15-22.

C2/3, C3

C3/4, C4/5, C4

C6/7, C6, C7

C2/3, C3/4, C3

C4/5, C5/6, C4, C5

C4/5, C5/6, C4

C7/T1, C7

Referred Pain Patterns

Bibliography• Barnsley L, Lord SM, Wallis BJ, Bogduk N. The prevalence of chronic

cervical zygapophysial joint pain after whiplash. Spine 1995;20:20-25.

• Bogduk N. Post whiplash syndrome. Australian Family Physician 1994;23:2303-2307.

• Brault JR, Wheeler JB, Siegmund GP, Brault EJ. Clinical response of human subjects to rear-end automobile collisions. Archives of Physical Medicine and Rehabilitation 1998;79:72-80.

• Eichberger A, Darok M, Steffan H, Leinzinger PE, et al. Pressure measurements in the spinal canal of post-mortem human subjects during rear-end impact and correlation of results to the Neck Injury Criterion (NIC). Traffic Safety and Auto Engineering Stream of the World Congress on Whiplash-Associated Disorders, 1999:345-359.

• Farmer CM, Wells JK, Werner JV. Relationship of head restraint positioning to driver neck injury in rear-end crashes. Traffic Safety and Auto Engineering Stream of the World Congress on Whiplash-Associated Disorders, 1999:70-89.

Continued…

• Fukui S, Ohseto K, Shiotani M et al. Referred pain distribution of the cervical zygapophysial joints and cervical dorsal rami. Pain 1996;68:79-83.

• Grauer JN, Panjabi MM, Cholewicki J, Nibu K, Dvorak J. Whiplash produces an s-shaped curvature of the neck with hyperextension at lower levels. Spine 1997;22:2489-2494.

• Insurance Institute for Highway Safety, Press Release, April 7, 1998. • Insurance Institute for Highway Safety, Status Report, 1997. 32(4).• Insurance Institute for Highway Safety, Status Report, 1999. 34(5).• Kaneoka K, Ono K, Inami S, Hayashi K. Motion analysis of cervical vertebrae

during simulated whiplash loading. Traffic Safety and Auto Engineering Stream of the World Congress on Whiplash-Associated Disorders 1999:152-160.

• Kornhauser M. Delta-V thresholds for cervical spine injury. 1996, SAE 960093.• Kumar S, Narayan Y, Amell T. Role of awareness in head-neck acceleration in low

velocity rearend impacts. Compendium of papers presented at the Traffic Safety and Auto Engineering Stream, World Congress on Whiplash-Associated Disorders 1999;276-296.

• Lord SM, Barnsley L, Wallis BJ, Bogduk N. Chronic cervical zygapophysial joint pain after whiplash: a placebo-controlled prevalence study. Spine 1996;21(15):1737-1745.

Continued…

Lord SM, Barnsley L, Wallis BJ, et al. Percutaneous radio-Lord SM, Barnsley L, Wallis BJ, et al. Percutaneous radio-frequency neurotomy for chronic cervical zygapophysial joint frequency neurotomy for chronic cervical zygapophysial joint pain. New England Journal of Medicine 1996;335(23):1721-pain. New England Journal of Medicine 1996;335(23):1721-1726.1726.

Matsushita T, Sato TB, Hirabayashi K, et al. X-ray study of the Matsushita T, Sato TB, Hirabayashi K, et al. X-ray study of the human neck motion due to head inertia loading. 38thhuman neck motion due to head inertia loading. 38th Stapp Stapp Car Crash Conference 1994; SAE 942208.Car Crash Conference 1994; SAE 942208.

Ono K, Kaneoka K, Wittek A, Kajzer J. Cervical injury Ono K, Kaneoka K, Wittek A, Kajzer J. Cervical injury mechanism based on the analysis of human cervical vertebral mechanism based on the analysis of human cervical vertebral motion and head-neck-torso kinematics during low speed rear motion and head-neck-torso kinematics during low speed rear impacts. Society of Automotive Engineers, 41impacts. Society of Automotive Engineers, 41stst STAPP Car STAPP Car Crash Conference Proceedings 1997; SAE 973340.Crash Conference Proceedings 1997; SAE 973340.

Ortengren T, Hansson HA, Lovsund P, et al. Membrane leakage Ortengren T, Hansson HA, Lovsund P, et al. Membrane leakage in spinal ganglion nerve cells induced by experimental in spinal ganglion nerve cells induced by experimental whiplash extension motion: a study in pigs. Journal of whiplash extension motion: a study in pigs. Journal of Neurotrauma 1996;13(3):171-180.Neurotrauma 1996;13(3):171-180.

Robbins MC. Lack of relationship between vehicle damage and Robbins MC. Lack of relationship between vehicle damage and occupant injury. SAE 970494.occupant injury. SAE 970494.

Siegmund GP, Brault JR, Wheeler JB. The relationship between Siegmund GP, Brault JR, Wheeler JB. The relationship between clinical and kinematic responses from human subject testing clinical and kinematic responses from human subject testing in rear-end automobile collisions. Traffic Safety and Auto in rear-end automobile collisions. Traffic Safety and Auto Engineering Stream of the World Congress on Whiplash-Engineering Stream of the World Congress on Whiplash-Associated Disorders, 1999:181-207.Associated Disorders, 1999:181-207.

Siegmund GP, King DJ, Lawrence, JM, et al. Head/neck Siegmund GP, King DJ, Lawrence, JM, et al. Head/neck kinematic response of human subjects in low-speed rear-end kinematic response of human subjects in low-speed rear-end collisions. Society of Automotive Engineers, 41collisions. Society of Automotive Engineers, 41stst STAPP Car STAPP Car Crash Conference Proceedings 1997; SAE 973341.Crash Conference Proceedings 1997; SAE 973341.

Continued…

Szabo TJ, Welcher JB. Human subject kinematics and Szabo TJ, Welcher JB. Human subject kinematics and electromyographic activity during low speed rear impacts. electromyographic activity during low speed rear impacts. 40th40th Stapp Car Crash Conference, SAE 962432.Stapp Car Crash Conference, SAE 962432.

van den Kroonenberg A, Philippens M, Cappon H, et al. Human van den Kroonenberg A, Philippens M, Cappon H, et al. Human head-neck response during low-speed rear end impacts. 42head-neck response during low-speed rear end impacts. 42ndnd Stapp Car Crash Conference Proceedings (P-227), 1998. SAE Stapp Car Crash Conference Proceedings (P-227), 1998. SAE 983158.983158.

Viano DC, Gargan MF. Headrest position during normal driving: Viano DC, Gargan MF. Headrest position during normal driving: implication to neck injury risk in rear crashes. Accident implication to neck injury risk in rear crashes. Accident Analysis and Prevention 1996;28(6):665-674.Analysis and Prevention 1996;28(6):665-674.

Wallis BJ, Bogduk N. Faking a profile: can naïve subjects Wallis BJ, Bogduk N. Faking a profile: can naïve subjects simulate whiplash responses? Pain 1996;66:223-227.simulate whiplash responses? Pain 1996;66:223-227.

Wallis BJ, Lord SM, Barnsley L, Bogduk N. Pain and psychologic Wallis BJ, Lord SM, Barnsley L, Bogduk N. Pain and psychologic symptoms of Australian patients with whiplash. Spine symptoms of Australian patients with whiplash. Spine 1996;21(7):804-810.1996;21(7):804-810.

Wallis BJ, Lord SM, Barnsley L, Bogduk N.The psychological Wallis BJ, Lord SM, Barnsley L, Bogduk N.The psychological profiles of patients with whiplash-associated headache. profiles of patients with whiplash-associated headache. Cephalgia 1998;18:101-105.Cephalgia 1998;18:101-105.

Wallis BJ, Lord SM, Bogduk N. Resolution of psychological Wallis BJ, Lord SM, Bogduk N. Resolution of psychological distress of whiplash patients following treatment by distress of whiplash patients following treatment by radiofrequency neurotomy: a randomised, double-blind, radiofrequency neurotomy: a randomised, double-blind, placebo-controlled trial. Pain 1997;73:15-22.placebo-controlled trial. Pain 1997;73:15-22.

Yoganandan N, Pintar FA, Cusick JF. Biomechanical analyses of Yoganandan N, Pintar FA, Cusick JF. Biomechanical analyses of whiplash injuries using experimental model. Traffic Safety and whiplash injuries using experimental model. Traffic Safety and Auto Engineering Stream of the World Congress on Whiplash-Auto Engineering Stream of the World Congress on Whiplash-Associated Disorders 1999:325-343.Associated Disorders 1999:325-343.

Live Occupant Footage Credit

The crash test footage is copyrighted by Biomechanics Research and Testing. Permission to use this footage was generously provided by:

Biomechanics Research and Testing, LLC1827 Ximeno Ave Ste 2Long Beach, CA 90815

Phone: (562) 494-8310Fax: (562) 494-4412

The video they produce contains crash test footage of five collisions between 1-6 miles per hour, and includes all of the data gathered during the crash tests.