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What Causes Whiplash?

Whiplash is most commonly caused by a motor vehicle accident in which the car the person is riding in is not moving, and is struck from a vehicle from behind without notice. It is commonly thought the rear impact causes the head and neck to be forced into hyperextension as the seat pushes the person's torso forward - and the unrestrained head and neck fall backwards. After a short delay the head and neck then recover and are thrown into a hyperflexed position.

More recent studies investigating high-speed cameras and sophisticated crash dummies have determined that after the rear impact the lower cervical vertebrae (lower bones in the neck) are forced into a position of hyperextension while the upper cervical vertebrae (upper bones in the neck) are in a hyperflexed position. This leads to an abnormal S-shape in the cervical spine after the rear impact that is different from the normal motion. It is thought that this abnormal motion causes damage to the soft tissues that hold the cervical vertebrae together (ligaments, facet capsules, muscles).

LOSRIC - A Common Collision

LOSRIC - Low Speed Rear Impact Collisions

• At crash speeds of 15-20 mph, spinal fractures and spinal cord injuries are not uncommon.
• Usually occurs in shorter distances and at lower speeds, which are characteristics of heavy traffic.

Biomechanics of LOSRIC

Sequence of events in LOSRIC:

• Bumper contact; seat strikes occupant
• Flattening of spinal curves; axial compression and ramping
• Head lag (retraction) phase; high shear, axial tension
• Head/neck extension phase; hight bending moments possible
• Forward (reentry) phase; head acceleration peaks, shear reverses
• Forward bending moments possible.