Background: To advance occupant protection through the improvement of safety countermeasures, it is necessary to understand the factors that affect human injury tolerance. This study investigated the effect of 'occupant factors' i.e. age, gender, height, weight, and body mass index (BMI) on the pattern of lower extremity injury after motor vehicle crashes (MVCs). The second objective was to identify factor(s) (including restraint systems and Delta V) that influence the severity of fractures (open versus close fractures) within the lower extremity area. The outcome of this study may have implications toward secondary prevention in MVCs.
Methods: One-hundred and thirty-seven front-seat occupants involved in MVCs with frontal impact admitted to the University of Michigan trauma center as part of the Crash Injury Research and Engineering Network (CIREN) project were evaluated. Injuries were classified according to location (knee, thigh, hip [KTH]; lower leg [LL], foot and ankle [FA]). All the relevant variables mentioned above were analyzed.
Results: KTH fractures were the most common region (49.5%) affected, followed by fractures to the FA (38.4%) and LL region (12.1%). Female occupants, being generally shorter than their male counterpart, sustained a significantly higher percentage of FA fractures (44% vs. 29.5%, p < 0.05). Male occupants sustained more KTH fractures (58.3% vs. 44%, p < 0.05). Results demonstrated that there were significantly higher percentages of 'open' fractures in the below knee area (FA [53.8%], LL [24.4%], and KTH [21.8%]; p < 0.05). Of all those variables tested (age, gender, height, weight, BMI, restraint systems, and Delta V), occupant's height had a significant effect on the severity of fractures sustained.
Conclusion: The interactive effect observed for height and gender on the pattern of lower extremity fracture is principally related to the body habitus and that gender may be a 'proxy' variable. The 'human factor' plays a vital role in influencing the pattern of injury in a MVC. This study strongly supports the fact that occupants with dissimilar body habitus interact differently with the interior cabin of the vehicle, thus, the performance of the active and passive safety systems.