Distinguishing injury patterns in pedestrian motor vehicle collisions from fall-from-height impacts. Medico-legal implications.

Introduction: Worldwide, road traffic accidents and falls from heights (FFHs) are commonly reported causes of morbidity and mortality. Given the lack of studies differentiating pedestrian motor vehicle (PMV) injuries from FFH, this study aimed to investigate the medicolegal aspects distinguishing the PMV injuries (horizontal impact) from FFH injuries (vertical high impact), especially in cases with no witnesses.

Methods: This prospective study was conducted among patients diagnosed with PMV collision, and FFH admitted to a Tertiary Emergency Hospital over two years.

Results: In this study, we enrolled 300 patients showing an overall mortality rate of 19%, which was higher in PMV impacts (20.7%) compared to FFHs (17.3%). While the trunk was the most commonly involved anatomical site among victims of PMV collisions (42%), the FFH was more significantly associated with scalp injuries that constituted the most common injury pattern in FFH impacts (62.7%, p < 0.001). A proposed model differentiating PMV injuries from FFH, exhibiting good performance with Nagelkerke's R of 0.688 and p < 0.00, showed that involvement of lower limbs, mainly bilateral leg wounds and unilateral thigh fractures, increased the odds of PMV accidents. In contrast, other axial injuries affecting the upper half of the body, like skull fractures, unilateral lung injury, and the presence of free intraperitoneal fluid, besides the unilateral forearm fractures, decrease the likelihood of PMV accidents and favor the diagnosis of FFH.

Conclusions: Axial trauma involving the upper part of the body and skull fractures increases the probability of FFH, while the lower limb soft tissue injuries and fractures are more associated with PMV accidents. The obtained finding should be interpreted cautiously, considering all available circumstances, keeping in mind that mechanism of trauma can cause almost any injury.