Uniaxial and biaxial mechanical properties of porcine linea alba

Abstract

Trocar site hernia (or incisional hernia) is a severe complication post laparoscopic surgery that is commonly associated with the linea alba. However, the few studies on the mechanical properties of the linea alba in the literature appear contradictory, possible due to challenges with the physical dimensions of samples and variations in protocol. This study focuses on the tensile mechanical characterisation of the porcine linea alba, as determined by uniaxial and equi-load biaxial testing using image-based strain measurement methods. Results show that the linea alba demonstrated a non-linear elastic, anisotropic behaviour which is often observed in biological soft tissues. The transverse direction (parallel to fibres) was found to be approximately 8 times stiffer than the longitudinal (cross-fibre) direction under both uniaxial and equi-load biaxial loading. The equi-load biaxial tensile tests revealed that contraction could occur in the transverse direction despite increasing load, probably due to the anisotropy of the tissue. Optical surface marker tracking and digital image correlation methods were found to greatly improve the accuracy of stretch measurement, resulting in a 75% change in the apparent stiffness compared to using strain derived from machine cross-head displacement. Additionally, a finite element model of the experiments using a combination of an Ogden and fibre exponential power law model for the linea alba was implemented to quantify the effect of clamping and tissue dimensions (which are suboptimal for tensile testing) on the results. The preliminary model results were used to apply a correction factor to the uniaxial experimental data prior to inverse optimisation to derive best fit material parameters for the fibre reinforced Ogden model. Application of the model to the equi-load biaxial case showed some differences compared to the experimental data, suggesting a more complex anisotropic model may be necessary to capture biaxial behaviour. These results provide an improved assessment of the mechanical properties of the porcine linea alba for wound closure and other studies.

Abdominal wall muscle elasticity and abdomen local stiffness on healthy volunteers during various physiological activities

“…Numerous experimental studies were conducted to characterize ex vivo the mechanical response of the abdominal wall (Junge et al, 2001;Podwojewski et al, 2013Podwojewski et al, , 2014 or its components (Ben Abdelounis et al, 2013;Cooney et al, 2015;Förstemann et al, 2011;Grässel et al, 2005;Hollinsky and Sandberg, 2007;Kirilova et al, 2011;Korenkov et al, 2001;Lyons et al, 2014;Martins et al, 2012;Rath et al, 1996;Tran et al, 2014;Wolloscheck et al, 2004). However, in vivo examinations are required to take into consideration muscle activity and to study patterns of muscle activation during different tasks and postures using electromyography (Brown and McGill, 2010;Crommert et al, 2011;McCook et al, 2009;Urquhart et al, 2005;Vera-Garcia et al, 2007).…”

Developing a new methodology to characterize in vivo the passive mechanical behavior of abdominal wall on an animal model

“…The longitudinal section was measured along the linea alba, where the junction between fascias and rectus abdominis lies moderately constant and the small differences between stretching of the segments can be explained due to the changes in the stretch response of the linea alba along its length (Cooney et al, 2015). However, cross-section goes through three different composite muscle layers besides the linea alba: rectus abdominis (segments C & D), external-internal composite (segments B & E) and external-internal-transversal composite (segments A & F) (Hernández-Gascón et al, 2011).…”

“…abdominal fascia, individual abdominal muscles or skin. Most of them have been performed on animal models, using pigs (Lyons et al, 2014;Cooney et al, 2015), dogs (Greca et al, 2001;Hwang et al, 2005) or rabbits (Hernández et al, 2011;Peeters et al, 2013), and a few others on humans (Kirilova et al, 2011;Förstemann et al, 2011;Martins et al, 2012;Ben Abdelounis et al, 2013). Nevertheless, when isolating one determined tissue from the whole, it may change the mechanical response of this tissue due to a loss of mechanical resistance.…”

A Constitutive Framework for Human Dermis Mechanical Modelling

“…Though authors have highlighted the challenges unique to biological tissues related to the planning and the performance of biaxial experiments, the limitations concerning the inadequacy of uniaxial tests in fully reproducing the in situ loading of soft tissues and in disclosing their profound anisotropy has been enhanced [6], [7]. Hence, both uniaxial [2], [4], [8]- [11] and biaxial [12]- [16] tensile tests are still being adopted aiming at investigating the mechanical properties of collagenous tissues, often in conjunction [6], [17]. The characterization of tissues mechanical response turns out to be fundamental also for the development of constitutive models and the subsequent definition of material properties exploitable in Finite Element (FE) studies.…”