During a rear-end automobile collision,
your body goes through an extremely rapid and intense acceleration
and deceleration. In fact, all four phases of a whiplash injury occur
in less than one-half of a second! At each phase, there is a
different force acting on the body that contributes to the overall
injury, and with such a sudden and forceful movement, damage to the
vertebrae, nerves, discs, muscles, and ligaments of your neck and
spine can be substantial.
Phase 1
During
this first phase, your car begins to be pushed out from under you,
causing your mid-back to be flattened against the back of your seat.
This results in an upward force in your cervical spine, compressing your
discs and joints. As your seat back begins to accelerate your torso
forward, your head moves backward, creating a shearing force in your
neck. If your head restraint is properly adjusted, the distance your
head travels backward is limited. However, most of the damage to the
spine will occur before your head reaches your head restraint. Studies
have shown that head restraints only reduce the risk of injury by
11-20%.
Phase 2
During
phase two, your torso has reached peak acceleration - 1.5 to 2 times
that of your vehicle itself - but your head has not yet begun to
accelerate forward and continues to move rearward. An abnormal S-curve
develops in your cervical spine as your seat back recoils forward,
much like a springboard, adding to the forward acceleration of the
torso. Unfortunately, this forward seat back recoil occurs while your head is still moving backward,
resulting in a shearing force in the neck that is one of the more
damaging aspects of a whiplash injury. Many of the bone, joint, nerve,
disc and TMJ injuries that I see clinically occur during this phase.
Phase 3
During
the third phase, your torso is now descending back down in your seat
and your head and neck are at their peak forward acceleration. At the
same time, your car is slowing down. If you released the pressure on
your brake pedal during the first phases of the collision, it will
likely be reapplied during this phase. Reapplication of the brake causes
your car to slow down even quicker and increases the severity of the
flexion injury of your neck. As you move forward in your seat, any
slack in your seat belt and shoulder harness is taken up.
Phase 4
This
is probably the most damaging phase of the whiplash phenomenon. In
this fourth phase, your torso is stopped by your seat belt and shoulder
restraint and your head is free to move forward unimpeded. This
results in a violent forward-bending motion of your neck, straining the
muscles and ligaments, tearing fibers in the spinal discs, and
forcing vertebrae out of their normal position. Your spinal cord and
nerve roots get stretched and irritated, and your brain can strike the
inside of your skull causing a mild to moderate brain injury. If you
are not properly restrained by your seat harness, you may suffer a
concussion, or more severe brain injury, from striking the steering
wheel or windshield.
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