Uniaxial and Biaxial Mechanical Properties of Porcine Linea Alba

Trocar site hernia (or incisional hernia) is a severe complication postlaparoscopic surgery that is commonly associated with the linea alba.However, the few studies on the mechanical properties of the linea alba inthe literature appear contradictory, possible due to challenges with thephysical dimensions of samples and variations in protocol. This studyfocuses on the tensile mechanical characterisation of the porcine lineaalba, as determined by uniaxial and equi-load biaxial testing usingimage-based strain measurement methods. Results show that the linea albademonstrated a non-linear elastic, anisotropic behaviour which is oftenobserved in biological soft tissues. The transverse direction (parallel tofibres) 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 occurin the transverse direction despite increasing load, probably due to theanisotropy of the tissue. Optical surface marker tracking and digital imagecorrelation methods were found to greatly improve the accuracy of stretchmeasurement, resulting in a 75% change in the apparent stiffness comparedto using strain derived from machine cross-head displacement. Additionally,a finite element model of the experiments using a combination of an Ogdenand fibre exponential power law model for the linea alba was implemented toquantify the effect of clamping and tissue dimensions (which are suboptimalfor tensile testing) on the results. The preliminary model results wereused to apply a correction factor to the uniaxial experimental data priorto inverse optimisation to derive best fit material parameters for thefibre reinforced Ogden model. Application of the model to the equi-loadbiaxial case showed some differences compared to the experimental data,suggesting a more complex anisotropic model may be necessary to capturebiaxial behaviour. These results provide an improved assessment of themechanical properties of the porcine linea alba for wound closure and otherstudies.