Background: Road traffic accidents are a major problem, causing death and injury in Thailand.

Objective: To study the relationship between external injury and internal injury which helps to diagnose severe cases caused by road traffic accidents and provides the information to reduce the chance of misdiagnosis.

Material and Method: The data of age, gender, external injury, the type of injury, internal injury, and the type of internal injury was gathered from 439 autopsy cases which affected regions of head, neck, chest, abdomen, and extremities. Chi-square and Binary Logistic Regression were used to analyses the relationship.

Results: The injury that had the greatest relationship with age was internal chest injury (p = 0.002), which was rarely found in children and was more common in the elderly. Males tended to have more head injuries than females (p = 0.003). The major cause of death from traffic accidents was head injury. Internal neck injuries depended on the position of the wounds nearby and the majority of injuries were caused by accelerate-decelerate mechanism. Multiple types of wounds or lacerated wounds could help to predict internal injury to head (p<0.001, p = 0.001), abdomen (p = 0.001, p = 0.013), and extremities (p<0.001, p<0.001). Abrasion wounds were the most common wound caused by traffic accident. Internal chest, neck or abdomen injuries had a relationship with internal injuries in the nearby anatomical regions (p<0.05). The external injury was found to relate to internal injury (p<0.05). However, the results should be interpreted with caution, because in some cases, in many regions, external injuries could not be found but internal injuries were present.

Conclusion: External injury was found to be related to internal injury. There was a relationship between gender and head injury whereby males had a significantly higher number of internal head injuries.

Keywords: Wounds, Traffic injury, Internal injury, External injury