Motor vehicle accidents (MVA) subject passengers to violent forces that can injure bones, ligaments, muscles, joints, intervertebral discs, and nerves. Many of these injures are not visible on routine x-rays but can produce considerable log term pain and disability. The whiplash mechanism during rear impact motor vehicle accidents (i.e. acceleration force from behind) are generally considered in 4 phases. During the first phase the car seat impacts with the spine producing compression and S-shaped curvature of the cervical spine. During phase 2, the head moves backward and stretches the anterior ligaments and compresses the posterior aspect of the discs and the posterior facet joints. IN phase 3, the head rotates forward and may injure the ligaments that attach the head to the cervical spine. During phase 4, the forces reverse and the neck bends forward, tearing the posterior ligaments and facet joints capsules and compressing the intervertebral discs producing disc herniation and nerve compression.
The direction and magnitude of the forces applied will determine the location and severity of injuries resulting from motor vehicle accidents. It is important to understand the biomechanics of motor vehicle accidents and how they can produce injury to tissues that are not visible using conventional X-rays. Radiologists with specific training and experience with radiologic evaluation of post-traumatic injuries is an important asset for the evaluation of personal injuries.