Experimental study of the mechanical properties of human abdominal fascia.

The aim of the study is to characterise mechanical properties of human abdominal fascia according to its direction of loading and localization. The one-dimensional tensile behaviour of human abdominal fascia and its orthotropy has been studied experimentally using human umbilical (UF) and transversalis fascia (FT). The specimens have been cut and stretched parallel and orthogonal to the main fibre bundles. 90 specimens 10 mm wide and up to 70 mm long have been tested. The following mechanical parameters, characterising tensile properties of human abdominal fascia, have been calculated from the obtained stress-stretch ratio curves: maximal stress T(L)(max), stretch ratio at maximal stress λ(T(max)), maximal stretch ratio at failure λ(max), and a secant modulus E(i). The tissue strips obtained from defined areas reveal break stress between 0.63 and 1.99 MPa for FT and 0.93-1.61 MPa for UF. The parameter estimation has shown that in the physiological strain range specimens from both type of fascia can be considered orthotropic material according to their secant module, maximum stress T(L)(max) and stretch at maximum stress. Anisotropy factor AF (ratio of the stress in longitudinal and transverse directions) has been used to establish the level of the orthotropy of material and its variations with the stretch ratio. The maximum AF is 4.3 for FT at 20% deformation and 3.3 for UF at 5% deformation. The differences between the mechanical properties of FT and UF according to localization are not statistically significant thus the mechanical properties of human abdominal fascia are not affected by the localization.