Delta V, principal direction of force, and restraint use contributions to motor vehicle crash mortality.

Objective: To measure the combined contribution of change in velocity (Deltav), principal direction of force (PDOF), and restraint use on mortality after vehicular trauma.

Methods: The Crash Injury Research and Engineering Network population includes patients <8 years old with one injury with an Abbreviated Injury Scale score >or=3 or with two injuries with an Abbreviated Injury Scale score >or=2, who were occupants of a vehicle. Patients 15 years or younger; in rear collisions; back seat occupants; in crashes with Deltav >80 km/h, unknown Deltav, or unknown PDOF; or in vehicles without airbags were excluded. Mortality was analyzed in relation to Deltav (km/h), restraint use, and PDOF using chi2. Multiple logistic regression models were built, including possible confounders (body mass index, age, gender) and interactions were explored. An [alpha] = 0.05 was used for all statistics.

Results: A total of 1,261 cases were included. Mortality was higher for unrestrained than for restrained patients (17% vs. 9%) and was higher for lateral than for frontal impact patients (17% vs. 11%). Higher mortality rates were also observed for Deltav 40-80 km/h than for Deltav <40 km/h (17% vs. 9%). Multiple logistic regression findings, after adjusting for age, gender, and body mass index, revealed significant effects of lateral PDOF (odds ratio [OR] 3.06 [2.03-4.61]), unrestrained status (OR 2.95 [2.01-4.38]), and Deltav 40-80 km/h (OR 3.65 [2.44-5.44]). Effect modification was found between PDOF and Deltav.

Conclusions: A Deltav 40 km/h to 80 km/h, lack of restraint use, and lateral impact significantly affects mortality. A synergistic effect was found between Deltav 40-80 km/h and lateral PDOF.