Correlation of Liver Injury and Biomechanical Predictors: A Study of Lateral and Oblique Impacts to Post‐Mortem Human Subjects

Research has shown that abdominal injuries account for 3‐5% of injuries from motor vehicle crashes. However, abdominal injuries, especially to the solid organs of the abdomen such as the liver, represent a higher proportion of serious injuries. Previous work has shown a correlation between vascular pressure and liver injury in human surrogates and in pressurized ex vivo human and porcine livers when subjected to blunt impact. The objectives of this work are to further investigate the relationship between pressure and liver njury using post‐mortem human surrogates. Specifically, the goals were to (1) conduct rigid impacts on PMHS (n=6) withre‐pressurized abdominal vascular systems and measure vascular pressure; (2) determine if a correlation exists between measured vascular pressure and liver injury; (3) compare the results with previously proposed biomechanical predictors of abdominal injury.

For the study, each PMHS was instrumented with pressure sensors in the abdominal vessels, including the abdominal aorta, the hepatic veins, and the inferior vena cava. The subject’s abdominal vessels were pressurized to physiological pressures using saline. For lateral impacts, the impact was applied to the right side of the subject. For oblique impacts, the impact was applied on the right side at 30 degrees anterior of lateral. The impact face was 30 cm by 15 cm. The lower edge of the impactor was aligned with the lowest rib at the mid‐axillary line, typically rib eleven.

The injuries observed to the liver were similar to those documented in the Crash Injury Research Engineering Network (CIREN) trauma database and included three livers with superficial lacerations to the capsule and one liver injury with a serious burst injury. Using binary logistic regression to predict the injury risk, various pressure related variables had statistically significant relationships to injury including peak change in pressure (P_max), peak rate of change of pressure (Pdot_max) as well as P_max*Pdot_max and [P(t)* Pdot(t)]_max. The most statistically significant model related the peak rate of change of pressure to serious abdominal injury. This variable was also strongly correlated to the kinetic analog of the viscous criterion which was found as the peak of the rate of change of force times the compression ([FdotC]_max). This suggests that the rate of change of pressure, similar to the kinetic analog of the viscous criterion, is a measurement of how quickly and how directly the liver is loaded. These results imply that pressure relates to injury and this could be used in an anthropomorphic test device (ATD) to predict abdominal injury. However, simply using a homogenous fluid filled insert for the abdomen may not be sufficient to determine if an organ would be injured or if it would move out of the way when impacted.