The range of collision speed in most (nearly 80%) rear impact whiplash injuries occur is 6-12 mph.
Early human volunteer crash testing simulating real world rear impact collisions was conducted at UCLA and demonstrated the volunteer's head was subjected to 2 1/2 times the acceleration as the vehicle itself.
Regarding the outcome of whiplash injuries, about 25-50% of whiplash injuries fail to resolve completely.
Risk factors for poor outcome in whiplash trauma are female gender, advanced age and nonawareness of impending impact.
- A possible explanation is that men have more neck musculature than women for about the same head size, so they're less susceptible to whiplash. Another hypothesis is that, because women tend to sit farther forward in their vehicle seats than men, their heads move farther to the rear in a crash before reaching a head restraint - a distance that has been associated with whiplash injuries.
- Awareness Preparedness for impact will greatly reduce the severity of injury in most cases of rear impact crash. For example, early crash test researchers demonstrated that by bracing for impact a human could reduce the forces to the head significantly. Drivers who were unaware of the impending impact were 20% more likely to be injured.
- This is probably attributable to a declining range of motion (ROM) in the neck, slower muscular reflexes, a decline in muscular strength, and the fact that injured tissues generally heal slower in older persons.
Concerning the risk of injury to children in rear impact motor vehicle collisions, children have been shown to have about 2/3 the risk of injury of adults.
- Young children are less frequently injured because their bodies are more supple and resilient and because their heads usually are protected by the relatively high seat back.
Although a fairly large percentage of persons will have symptoms on a permanent basis following whiplash injury, 10% of whiplash patients will have disability.
The majority of modern passenger cars behave relatively stiffly in low speed rear impact collisions. Permanent damage to bumpers systems begins to occur at 8-12 mph
The latest full scale rear impact crash tests using human volunteers, the threshold for cervical spine soft tissue injury is 5 mph.
When the body is twisted or the head is turned, or when the occupant is leaning forward or is in some other awkward position, injury is more likely.
Any preexisting disorder or anomaly (including previous whiplash injuries) involving the spine will most likely lend a negative influence as regards both the severity of the injury and the long term prognosis. Many conditions may be silent, however, including such things as spinal stenosis, mild spondylosis, congenital fusions, and residuals of healed prior injuries to name but a few. They will, in many cases, complicate healing and prolong the need for care.
Neck sprain or strain is the most serious injury in one-third of insurance claims for injuries in all kinds of crashes.
In Pain Research & Management. 2006 Summer;11(2):79-83. the authors studied 2,184 residents of Saskatchewan. Overall, 15.9% reported a history of neck injury from motor vehicle crash and this was more common in females in all age groups. Perhaps the most important aspect of this study was the association of various comorbidities with the history of neck injury from motor vehicle crash. The authors looked at allergy, breathing disorders, hypertension, cardiovascular disorders, digestive disorders, and low back pain. They found higher comorbidities in all categories except hypertension, and in many cases the reported complaints were close to twice the severity as those reported in persons with no history of neck injury. In addition, the impact of these comorbidities was greater on the lives of those suffering neck injury than among the uninjured. The authors found that the general health of those having been injured was significantly lower than in those who had not. In the neck injury history group, 9.9% suffered from disabling neck pain in the six month survey period vs. only 3.9% who had no history of neck injury. Headaches that moderately or severely affected the health were likewise more common among the MVC group (33.0%) than the non-motor vehicle crash group (15.2%).
