Poroviscoelastic modeling of liver biomechanical response in unconfined compression.

Mechanistic modeling approaches are important for understanding how fluid and solid components of the liver interact during impact trauma. This study uses poroviscoelasticity (PVE) theory to simulate liver biomechanical response in unconfined compression stress relaxation experiments, for variable ramp strain rates ranging from 0.001 to 0.1 s(-1). Specimens included 17 ex vivo porcine liver samples tested in a humidified temperature-controlled chamber. Liver response was modeled using ABAQUS, and best-fit parameters were determined using non-linear least-squares algorithms. The PVE model was able to capture the behavior of porcine liver in unconfined compression, with regression analyses for the ramp phase demonstrating high correlation between model and experiment (R(2) > 0.993, slope > 0.833, p < 0.05). The advantage of PVE modeling over traditional viscoelastic modeling is the ability to examine interstitial fluid pressure as a contributor to tissue mechanical response. This strategy creates new opportunities for quantifying an injury mechanism (burst injury) that is common in blunt abdominal trauma, and will lead to advancement of high-fidelity virtual crash test dummies, and improved vehicle safety.