When a human body is struck by a vehicle, it undergoes immense stress. The forces involved can deform tissues and organs beyond their normal limits, resulting in severe injuries. This trauma triggers immediate physiological responses. Damage can range from visible external wounds to profound internal destruction, impacting nearly every body system.
The Physics of Impact
A vehicle collision with a pedestrian involves a significant transfer of kinetic energy from the vehicle to the body. The impact’s severity relates to factors like the vehicle’s speed, mass, and strike angle. This energy transfer results in blunt force trauma.
The body experiences forces like acceleration-deceleration, where tissues and organs rapidly change speed, often leading to tearing or shearing. For instance, the brain can strike the inside of the skull during rapid deceleration. The distribution of force also plays a role; a concentrated force causes more severe localized damage than a force spread over a larger area. Tissues like skin, muscle, and bone have different tolerances and respond uniquely to these impacts.
Immediate Bodily Responses
Upon impact, the body initiates rapid physiological responses to manage acute stress. A sudden surge of adrenaline floods the bloodstream, preparing the body for a “fight or flight” response. This increases heart rate, blood pressure, and diverts blood flow to essential organs and muscles.
The body also enters a state of shock, a complex reaction to severe injury that can lead to inadequate blood flow to tissues. Pain signaling pathways are immediately activated, sending intense signals to the brain. This alerts the individual to severe damage.
Common Injury Patterns
When a pedestrian is struck by a vehicle, a range of common physical injuries occur, impacting various bodily systems. The specific injuries depend on factors like vehicle speed, impact angle, and the pedestrian’s age.
Skeletal and Muscular Injuries
Skeletal and muscular injuries are frequent, often including fractures of long bones in the legs, pelvis, and ribs. The intense force can also cause dislocations, where bones are forced out of their joints. Severe soft tissue damage, such as muscle tears, strains, and ligament ruptures, can occur, particularly in the neck (whiplash) and shoulders.
Head and Brain Injuries
Head and brain injuries are severe consequences. These include concussions, resulting from the brain shaking inside the skull and leading to symptoms like confusion, dizziness, and headaches. Skull fractures may also occur from a direct blow. More serious traumatic brain injuries (TBIs) encompass intracranial hemorrhages and diffuse axonal injury (DAI), where nerve fibers are torn due to rotational forces.
Spinal Cord Injuries
Spinal cord injuries are a serious concern, resulting from fractures to the vertebrae or direct damage to the spinal cord. These injuries can compress, twist, or sever the spinal cord, potentially leading to severe back pain, weakness, loss of coordination, or paralysis below the injury site.
Internal Organ Damage
Internal organ damage often results from blunt force trauma to the chest and abdomen. In the chest, injuries can include myocardial contusions, pulmonary contusions, and broken ribs, which can sometimes puncture a lung. Abdominal trauma can lead to contusions, lacerations, or ruptures of organs like the liver, spleen, and kidneys.
Skin and Soft Tissue Injuries
Skin and soft tissue injuries are common, ranging from abrasions, lacerations, avulsions, and crush injuries. These external injuries can sometimes conceal more significant internal damage.
Long-Term Physical Consequences
The physical impact of being hit by a car can extend beyond the immediate aftermath, leading to enduring challenges. Chronic pain is a common long-term consequence, often resulting from nerve damage, inflammation, or persistent muscle tension. This pain can affect daily activities and persist for months or years.
Limited mobility frequently results from severe musculoskeletal injuries, such as poorly healed fractures or extensive soft tissue damage. Joint injuries, including those to the ankles, knees, wrists, and hips, can contribute to post-traumatic arthritis, a condition where joint cartilage deteriorates over time due to the initial trauma. This can cause ongoing pain, swelling, and stiffness in the affected joints.
Neurological deficits can persist, especially following traumatic brain injuries or spinal cord damage. These may include cognitive issues such as memory loss, difficulty concentrating, or impaired decision-making. Motor control problems, including weakness, balance issues, or partial or complete paralysis, can significantly alter an individual’s independence. Organ dysfunction may also be a lasting issue, particularly if internal injuries were extensive or led to complications.