Assessment of the ultimate strain of the hepatic capsule for the prediction of liver surface laceration

IRCOBI conference, Lyon, France, 09-/09/2015 - 11/09/2015In the field of road safety, the prediction of abdominal injuries is a relevant issue, especially considering rear ? seat passengers such as children, elderly or obese individuals. Among abdominal organs, the liver is particularly vulnerable due to its weight and location. Moreover, the liver which is highly vascularized has a high level risk of severe hemorrhage when injured. Considering its three main components ? parenchyma, capsule and a dense vascular network - this complex organ has three main types of injury: hematoma, laceration and vascular failure. The liver also has a high level of variability in terms of geometry and mechanical properties which makes it difficult to model. The variability of mechanical properties of hepatic tissues is closely related to individual variability and to potential diseases of patients such as the case of steatotic liver due to obesity or diabetes, for which parenchyma is especially fragile. Global injury criteria were established on whole pressurized organs in terms of impact energy, impact velocity and peak pressure. Local mechanisms of vascular/parenchyma injuries during a freefall and severe frontal deceleration were also highlighted but not quantified in terms of local criteria. The present study focuses on liver surface laceration, involving capsule and parenchyma. The hypothesis of the authors is that this type of injury occurs because of an excessive pressure and thus an important tension on the liver surface during an impact. Thus, local failure criteria of the capsule and superficial parenchyma must be defined in view of the prediction of surface laceration occurrence. For a few years, the co ? authors, members of the French research network Impact Biomechanics Research Group, studied the mechanical behavior of hepatic tissues up to failure. In a first step, uniaxial and equibiaxial tensile tests were performed on isolated samples of capsule ? parenchyma and capsule in order to quantify the ultimate mechanical properties of the capsule. In a second step, the capsule pretension before sampling was assessed on isolated liver under various internal fluid pressures. During all these tests, the surface strain fields were measured on the hepatic capsule by digital image correlatio