Anisotropy of human linea alba: a biomechanical study

Recently, a new model of fiber architecture of the linea alba has been described consisting of an oblique fiber layer of intermingling oblique fibers, a transverse fiber layer containing mainly transverse fibril bundles, and a variable, small irregular fiber layer. In this study the morphological model was proven using direction-specific biomechanical measurements of the linea alba.

Thirty-one human abdominal walls were analyzed (16 male and 15 female). Six strips of collagen tissue with a width of 1 cm were exsected from each linea alba transversely, obliquely, and longitudinally according to the main fiber directions. An increasing force from 2 to 24 N was applied to these strips, and the corresponding strain represented by the relative elongation was measured, which allows the calculation of a direction-specific compliance of the tissue.

The compliance is highest in longitudinal and smallest in transverse direction. In the infraumbilical part of the female linea alba the compliance was significantly smaller in the transverse direction than in the oblique direction. Moreover, the compliance in the transverse direction was significantly smaller in women than in men.

A distinct anisotropy of morphological and biomechanical properties was demonstrated as well as sex-dependent differences. The compliance correlates with the distribution of fiber orientation in the linea alba. These biomechanical results constitute the functional correlation with the fiber morphology of the linea alba and correspond well to our earlier proposed model of fiber architecture.