Biomechanical Properties of Abdominal Organs In Vivo and Postmortem Under Compression Loads

Abstract

Accurate knowledge of biomechanical characteristics of tissues is essential for developing realistic computer-based surgical simulators incorporating haptic feedback, as well as for the design of surgical robots and tools. As simulation technologies continue to be capable of modeling more complex behavior, an in vivo tissue property database is needed. Most past and current biomechanical research is focused on soft and hard anatomical structures that are subject to physiological loading, testing the organs in situ. Internal organs are different in that respect since they are not subject to extensive loads as part of their regular physiological function. However, during surgery, a different set of loading conditions are imposed on these organs as a result of the interaction with the surgical tools. Following previous research studying the kinematics and dynamics of tool/tissue interaction in real surgical procedures, the focus of the current study was to obtain the structural biomechanical properties (engineering stress-strain and stress relaxation) of seven abdominal organs, including bladder, gallbladder, large and small intestines, liver, spleen, and stomach, using a porcine animal model. The organs were tested in vivo, in situ, and ex corpus (the latter two conditions being postmortem) under cyclical and step strain compressions using a motorized endoscopic grasper and a universal-testing machine. The tissues were tested with the same loading conditions commonly applied by surgeons during minimally invasive surgical procedures. Phenomenological models were developed for the various organs, testing conditions, and experimental devices. A property database-unique to the literature-has been created that contains the average elastic and relaxation model parameters measured for these tissues in vivo and postmortem. The results quantitatively indicate the significant differences between tissue properties measured in vivo and postmortem. A quantitative understanding of how the unconditioned tissue properties and model parameters are influenced by time postmortem and loading condition has been obtained. The results provide the material property foundations for developing science-based haptic surgical simulators, as well as surgical tools for manual and robotic systems.

Characterization of the mechanical properties of resected porcine organ tissue using optical fiber photoelastic polarimetry

“…The experimentally determined range of elastic modulus values using the optical fiber PEP method and QLV fit is 0.1-0.5 KPa for liver, 0.15-0.9 KPa for kidney, and 0.2-8.0 KPa for pancreas. Our results are within the range of previously published elastic modulus values [1,2,[20][21][22][23][24]. Previously reported elastic modulus values vary due to several factors, including the animal model, sample preparation method, and mathematical fit used.…”

“…The result is a numerical solution for each of the five coefficients: A, B, C, 1 τ , and 2 τ . Example data sets and associated QLV model fits are presented in Fig.…”

“…Compressive testing is one of the most robust methods for measuring the mechanical properties of tissues due to the large range in Young's Modulus values, from 50Pa-5GPa [1,2]. However, current techniques either suffer from poor spatial resolution or require destructive sample processing.…”

In Vivo Measurement of Surface Pressures and Retraction Distances Applied on Abdominal Organs During Surgery

“…1210 Barrie et al 2016 108 attributed the force relaxation phenomenon in their work to a combination of a maximum force to lift the organ initially and subsequent tissue response and grasper handle applied pressure.…”

Dynamic Material Properties of Human and Animal Livers

“…5 The flow chart of our inverse finite element solution for estimating the hyper-viscoelastic material coefficients of pig liver [15] measurements are very limited. Most of the earlier studies have focused on the characterization of static and viscoelastic material properties of animal [2,4,14,15,18] and human livers [10], but not their frequency-dependent properties. Saraf et al [17] investigated the dynamic response of human liver in hydrostatic compression and simple shear using the Kolsky bar technique at high strain rates ranging from 300 to 5000 s .…”