Investigation of the Relationship between Pressure and Injury by Impacting Ex Vivo Perfused Spleens

Abstract

Motor vehicle crashes (MVCs) can be fatal and may induce permanent disability to the individuals involved. MVCs may result in injury to different body regions, but in particular, the abdomen is a site of life-threatening injuries due to housing vital body organs. The spleen is the second most injured abdominal organ following the liver, but the major causation of the splenic injuries remains largely unknown. Since the spleen is believed to have viscoelastic characteristics, sudden change in pressure during MVCs might be a source of these injuries. The main objective of the present study is to investigate the relationship between impact-induced pressure change and corresponding injuries in an ex vivo organ experimental model. Historically, there have been limited attempts to impact a pressurized ex vivo spleen; therefore, this study is one of the first times impact based tests are used to relate pressure changes to splenic injuries. The ex vivo spleens were instrumented with two miniature pressure sensors inside of foley catheters located in the splenic artery and vein. A perfusion system was developed to reproduce the physiological pressure of ex vivo spleens between 60-120 mmHg at steady state. Using an electromagnetic or hand trigger mechanism, an impact plate (23.4 kg) was dropped from varying heights to vary impact energies. The ex vivo spleens were impacted up to three times until gross injuries to the spleen occurred. The injuries were assessed according to the Abbreviated Injury Scale (AIS), and the probability of injury was plotted against pressure, velocity, and the rate of pressure change in the artery, Ṗartery. Gross injuries with AIS ≥3 to the ex vivo spleens occurred from pressures around 11 psi and from Ṗartery after 1057 psi/sec. The findings suggest that pressure and Ṗartery correspond well with injury severity, whereas velocity does not correspond well with injury severity. This study serves to show that pressure and Ṗartery may be used to predict injuries to the spleen during impact scenarios. Such relationships will help to better define abdominal injury criteria when simulating impacts to the abdomen of dummies or human finite element models.