It is common knowledge that accidents that occur at high speeds can cause significant damage and injuries. However, what is less commonly known is that low-impact collisions can be just as dangerous and damaging. Many studies have been conducted regarding low-impact collisions, both front- and rear-end crashes. The studies conclude that serious injuries do occur frequently in low-impact collisions, even when damage to the vehicle is minor.
Conservation of Linear Momentum
Conservation of linear momentum is one reason for common low-impact collision injuries, such as whiplash. This is the scientific explanation that when a body is in motion, it retains its total momentum unless an external force is applied. Newton’s First Law of Motion says that a body at rest tends to stay at rest, while a body in motion tends to remain in motion. In both cases, they remain at rest or in motion until an external, unbalanced force changes something. Newton’s Second Law says that a body’s acceleration is directly proportionate to the force and mass of the body, while Newton’s third Law says that for every force on the body, there is an equal but opposite force reacting as well. These laws of physics explain how serious injury can occur even when there is only slight damage to a vehicle.
Compared to a Fall
One way to get a feel for the forces involved in low-speed collisions is to compare the impact with a slip and fall. Most people have experienced a fall at some point in their lives, so it makes it easier for them to understand the forces involved in a vehicle crash. A fall from a desk that is three feet above the floor is equal to the impact of a 10 mile per hour change in speed. In other words, if a vehicle is traveling ten miles per hour and comes to an abrupt stop, the effect on the body is the equivalent of falling from the height if three feet onto the floor. By contrast, a 15 mile per hour speed change is the equivalent of falling from a seven-and-a-half foot stepladder, while a 20 mile per hour speed change is equal to falling more than 13 feet from a roof.
Compared to Other Actions
In some cases, experts have compared the impact to the head and neck during a collision to other actions, such as coughing or sneezing. Some have compared it to hopping onto a step or plopping down into a seat. However, these events do not take a person by surprise. When someone sneezes or coughs, their body automatically prepares the neck muscles for the action. The same is true when someone purposely drops into a chair or hops onto a step. In a collision, the body cannot properly prepare, even when the person is aware the impact is coming. The neck and back muscles cannot tense in preparation for sudden movement as they can during a sneeze, cough or other planned body movement.
Whiplash and Lower Back Injuries
Because of the way people sit in vehicles, the neck and lower back are more susceptible to injury in collisions. Because the head moves faster than cars when automobiles collide, whiplash and back injuries are common, even when vehicles are moving slowly. In fact, research has shown that an eight-mile-per-hour crash delivers 2g’s of force to a vehicle, but 5g’s of force to the head and neck. In order to determine the extent of injury, accident reconstruction experts often determine the conservation of linear momentum as well as the possible g-forces which occurred in the accident.
What happens if an MRI does not reveal significant soft-tissue injuries, but I am still in pain?
If there is no fractured or broken bones – a regular x-ray will not be of much help. If there is a lack of disc herniation or significant disc bulge, neither will an MRI scan.
The next place to look is ligament damage. Ligaments can be damaged at very low speeds, less than six miles-per-hour for C1 and C2 alar/traverse ligaments according to the latest research. Ligament damage can result in neck pain, nausea, headaches, difficulty sleeping and plenty of other painful symptoms. In order to find this kind of injury, the doctor has to know where to look. It’s in the x-ray. However, the person must be in certain positions (neck flexed and bending laterally to the left or right). The x-ray is taken though the open mouth in this stressed position.
If you are lucky, your doctor will have a digital-motion x-ray (often called a DMX). This is very similar to videofleuroscopy used by cardiologists to help guide heart catheterizations and, in a personal-injury lawyer context, pain-management settings to help guide epidural injections. As the name suggests, when using DMX, the medical provider can see the spine moving in real time…when there is damage to ligaments of the spine, abnormal movements can be seen. Intervertebral foramen may constrict with certain motions when the ligaments that hold these holes (where nerves enter and exit) tear or are weakened.
There is also a specialized MRI called, proton-density weighted sequence with fat suppression. Only with this type of MRI can ligaments be seen in the cervical spine – light grey if damaged (called a high-signal area due to the scar tissue that has built up in the damaged ligament), dark black if healthy. High-signal changes in the alar and transverse ligaments are common in auto accidents and generally are not considered old or degenerative changes (i.e. not necessarily likely to be seen as a natural progression of getting older).
Ligaments have nerve endings in them, so an injured ligament is painful. It is also permanent and, according the AMA, damaged ligaments are as severe as disc herniation.
Position Inside Vehicle
There are other factors that can also be used to determine the extent of injury in a low-impact collision. The way a person is positioned in the vehicle is also important and could be the reason for an injury. These can include:
- A turned head at the point of impact
- Head not aligned properly with the headrest
- Lower back not pressed against the seat’s lumbar support
Although these are just a few of the factors that can lead to injury during a crash, they can play a major role in the injuries sustained.
Angle of Vehicle
Another factor to consider when determining the extent of an injury after an accident is the angle of the vehicle when it was struck. If the car is struck more to the right or to the left, occupant’s spines can be subjected to rotational forces which can increase the risk of injury. If an occupant is leaning forward or turned in the seat in some way, they are also more likely to suffer spinal injuries, even if the accident appears minor.
Whiplash injuries are reported more often in rear-impact collisions than in front-impact collisions, despite improvements in vehicle safety such as head rests. Often, the vehicles involved sustain little or no damage and the occupants may not initially think they are injured. Because the interior of the vehicle and restraint systems impose specific force on the neck and torso, an unsupported head will cause the neck to extend, pulling ligaments and muscles of the cervical column. In low-speed impacts, some research indicates that whiplash injuries occur more often in rear-impact collisions as a consequence of neck flexion as the head rebounds from the seat back during the crash.
Females Injured More Often
A recent study found that female occupants are more likely to suffer from cervical injury after a low-speed rear-end collision and are more likely to suffer from chronic symptoms after such an injury. The study found that women are more likely to suffer such injury as their total motion is greater than men during an accident. Because women are smaller, an impact causes them to move in a vehicle more freely than men. Research also found that women who were able to prepare for the impact had 25 percent less head retraction than those who were unprepared and surprised by the impact. This confirms that drivers and passengers who are unaware of an impending crash are more likely to be injured than those who are able to brace for impact.
Determining Who Will Be Injured
Unfortunately, with so many variables that go into injuries from low-speed collisions, both front- and rear crashes, there is no scientifically valid method to determine who will be injured in a crash. Biomechanical engineers cannot say specifically that a specific g-force is necessary in order to cause whiplash or herniate a disc. Research varies on the amount of pressure required for disc herniation, with some stating it requires between 500 and 600 pounds of pressure, while others finding that it can take considerably less pressure to case damage. In addition, people with pre-existing disc injuries are more likely to herniate the same or an adjacent disc than those who have never had a disc injury.
Long-Lasting Effects of Whiplash
Research shows that approximately ten percent of occupants of a vehicle that is rear-ended will develop whiplash syndrome and another ten to fifteen percent will suffer from cervical soft tissue injures. Whiplash can persist for years even though evidence may not appear on x-rays or other tests. Currently, there are not definitive medical tests to identify deranged soft tissues. Impacts at as slow as five miles per hour have caused serious injuries to occupants. According to one report, slow or moderate collisions cause the maximum hyperextention of the neck and spine. In high speed collisions, the seat back is often broken, which actually minimizes theforce of hyperextension.
Role of Safety Features in Injuries
Vehicle manufacturers continue to add more and more safety features to cars designed to protect the driver and passenger from injure in a crash. However, some of these safety features may actually lead to injury. Spring-like rear bumpers increase rebound and reduce damage to the vehicle, but the occupant experiences a stronger neck snap, which can lead to soft tissue damage. In a rear-impact, the car that is hit from behind speeds up. This causes the occupants of the vehicle to experience higher speeds in order for the body to reach the same speed as the vehicle. When the vehicle stops abruptly, the occupant may still be moving to catch up with the car, which causes them to snap backwards into the seat. It is this rebound effect that researchers believe causes the most damage to the head and neck.
Injuries May Not Be Immediately Evident
It is not uncommon for the occupant of a vehicle that is struck at low-speeds to not immediately realize they have been injured. Symptoms can be delayed as much as 24 to 72 hours after an accident. However, some patients may notice a slight stiffening of the neck or minor pain in the back immediately. In many cases, they may brush off the pain as typical after an accident. Research shows that patients who feel pain in the neck and back immediately after a crash, even if the pain is minor, are more likely to suffer chronic pain as a result. Doctors say that immediate pain may indicate a more significant injury which can lead to chronic problems in the future. Anyone involved in a crash that loses any range of motion in their neck or back immediately after impact should be seen by medical professionals immediately.
Age as a Factor
Age is another factor in risk of injury during a low-speed collision. As people age, discs in their spines grow stiffer and reflexes slow down. In some cases, undiagnosed arthritis may have developed in joints. Older people also have less flexible muscles and ligaments. All of these factors lead to an increased risk of neck and spine injuries for older people. In addition, healing times for older adults are longer and many are less likely to tolerate minor sprains or strains.
Quite often, occupants of vehicles who claim injury after minor accidents are thought to be frauds, out to get the largest settlement possible. In some cases, others may believe that serious injury only occurs at high speeds. In addition, because whiplash and other soft tissue injuries sometimes do not appear on medical tests, others may not believe the injury actually occurred. Finally, because there have been many fraudulent claims regarding whiplash and soft tissue injuries, insurance companies or claims adjusters are cautious about accepting the word of the injured person.
One issue that faces someone who has been injured in a low-speed crash is that insurance companies sometimes set unreasonable standards when it comes to certain injuries. In the mid-1990s, one insurer published guidelines stating that vehicle crashes with less than $1,000 in property damage could not, or were unlikely to, cause significant or permanent injury. The insurance company directed claims adjustors to consider any such claim as fraudulent regardless of evidence of injury. In many cases, insurance companies focus on speed and a report from the Insurance Institute for Highway Safety stated that the likelihood of injury was directly dependent on the speed at impact.
Despite the belief of many that severe injuries cannot occur during low-speed collisions, research has shown otherwise. In addition, whiplash and other back injuries are common, especially in rear-end low-speed collisions. Because the term whiplash has received such negative connotations in the legal world, many attorneys no longer use it to describe injuries, instead using words like neck hyper-extension. Studies indicate that injuries from low-impact crashes can be serious and develop into chronic conditions, especially for women and the elderly. Learn more about low-impact injuries and what to do after suffering from one online.