The sheath of the rectus abdominis muscle: an anatomical and biomechanical study

Summary The anterior layer of the sheath of the rectus muscles is often used in the repair of incisional hernias through the linea alba. This practice has led us to undertake an anatomical and biomechanical study of its structure. Thirty fresh cadavers were divided into three groups of ten. All were dissected and biomechanical tests were carried out on the latter two groups: in Group 2 a dynamometer was used to measure the resistance to linear traction and to deformation. In Group 3 a bursting strength tester was used in order to determine the resistance to pressure. Morphological studies included measurements of the mean dimensions of the sheath, and of its composition at different levels. The biomechanical results show that the anterior sheath is more resistan to traction below the arcuate line than above it, whereas the resistance to pressure shows an opposite pattern. The resistance to traction of the posterior sheath is similar in its aponeurotic portion both above and below the umbilicus, the resistance to pressure being slightly less in the region of the arcuate line. The figures for deformation are essentially the same at all levels. The implications of these results for the repair of abdominal wall defects are discussed.