The abdominal linea alba: an anatomo-radiologic and biomechanical study.

Traditionally, the linea alba represents the principal route of approach in abdominal surgery and in consequence it is the commonest site of incisional hernia. The aim of this study was to review its morphology and to study its mechanical parameters of resistance, deformation and elasticity in order to compare these with the prosthetic materials most often used in the treatment of incisional hernia. Forty fresh cadavers were dissected and tests with a dynamometer and "bursting strength tester" were performed on samples taken from the linea alba at three levels: supra-umbilical, subumbilical and umbilical. Forty abdomino-pelvic scans were analysed. The morphologic results allowed definition of diastasis of the rectus mm. in terms of subject age: below 45 years of age diastasis was considered as a separation of the two rectus mm. exceeding 10 mm above the umbilicus, 27 mm at the umbilical ring and 9 mm below the umbilicus; above 45 years of age the corresponding values were 15 mm, 27 mm and 14 mm respectively. In the biomechanical study the subumbilical region exhibited a coefficient of elasticity greater than that of the supra-umbilical portion, but no significant difference in resistance was found between the different parts studied. The biomechanical results are compared with the corresponding data for prosthetic materials.