Biomechanical and morphological types of the linea alba and its possible role in the pathogenesis of midline incisional hernia.

OBJECTIVE: To review the tensile strength of the different histological types of fibres in the linea alba and correlate the anatomical features of the anterior abdominal wall with the tensile strength of the linea alba to see whether the tensile strength of the linea alba might contribute to the development of midline incisional hernias.

DESIGN: Laboratory study.

SETTING: University hospital, Germany.

SUBJECTS: 46 cadavers in part one, and 9 freshly frozen and 38 formalin-fixed cadavers in part two.

INTERVENTIONS: In the first part of the study the histological examination was by binocular dissection microscopy, magnification x10, but this was not sufficiently reproducible so in the second part we used an Olympus BX50 microscope, magnification x20, and Optimas 5.22 picture processing software. Tensile strength was measured using a Loosenhausen ZHP 1-6 tensiometer.

MAIN OUTCOME MEASURES: Correlation between anatomical features and tensile strength.

RESULTS: The method used in part one of the study failed to differentiate between the three types of fibres in the linea alba (weak, intermediate, and compact). In the second part of the study we found that the fibres were irregular, with no systematic crossing of the fibres of the aponeurosis. There was a significant correlation between the thickness and density of fibres in the linea alba and its tensile strength (r = 0.9). The thickness of fibres ranged from 21.9-38.2 microm and the density from 48% to 90%. The tensile strength ranged from 3-25 kp.

CONCLUSION: A combination of low density and thin fibres in the linea alba could be a predisposing factor for development of midline incisional hernias