Research has shown that abdominal injuries account for approximately 3-5% of all injuries that occur during motor vehicle collisions. However these injuries, especially to the solid organs of the abdomen like the liver, represent a much higher percentage of life threatening injuries. Research has suggested that in blunt liver trauma the mechanism of injury is linked to the rapid increase in internal pressure. Previous work also 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 impacts. The objective of this work is to further investigate the relationship between pressure and liver injury using full-body post-mortem human surrogates (PMHS) subjected to lateral and oblique impacts with boundary conditions more representative of motor vehicle collisions.
Specifically, the goals of this research were to (1) correct and re-analyze previous experimental work done by Sparks et al (2007) and Gustafson (2009); (2) continue work by Gustafson and complete an additional four rigid impacts to PMHS (for a total of n=10); (3) determine if a correlation exists between several pressure-related variables and liver injury from PMHS data and ex vivo work performed by Sparks et al; (4) compare the results to previously proposed biomechanical predictors of abdominal injury.
For the combined PHMS study, each PMHS was instrumented with pressure sensors in the abdominal vessels, these included: the abdominal aorta, the hepatic veins, and the inferior vena cava. The subjects’ abdominal vessels were pressurized to physiological pressures using saline. Using a pneumatic ram, all subjects were impacted at approximately 7.0 m/s at the estimated level of the liver. Autopsies were conducted on each subject following the impacts to determine the severity of injury to the PMHS and data from the pressure sensors were used to develop injury risk functions correlating pressure to the documented abdominal injuries.
The liver injuries observed in the combined PMHS study (n=10) were similar to those documented in the Crash Injury Research Engineering Network (CIREN) trauma database. Injuries included four livers with serious burst injuries and three livers with superficial lacerations to the capsule. Using binary logistic regression to develop injury risk functions, it was determined the peak rate of pressure change (Pdotmax) was a statistically significant predictor of AIS 3+ liver injury in both the PMHS and ex vivo testing. This suggests that Pdotmax is a good predictor for liver injury regardless of the impact boundary conditions. These results suggest that the peak rate of pressure change could be used in anthropomorphic test devices (ATDs) to predict abdominal injury.