Load on the Inguinal Region under Standard Conditions in Pigs

Objective: To find out the effect of standardised stress on the load of the inguinal region. Design: Experimental study. Setting: Surgical university clinic, Germany. Subjects: 15 uncastrated adult male pigs. Interventions: The tension force between the lateral edge of the rectus sheath and the base of the inguinal ligament was measured after simulation of the Shouldice repair. Standard stresses (coughing, straightening up into the upright position, small or large pneumoperitoneum, and electrical stimulation of abdominal muscles) were imposed. Main outcome measures: Intra-abdominal pressure and tension force in the inguinal region. Results: We found the highest (mean, SEM) intra-abdominal pressure during coughing (33.1, 5.2 mm Hg) with an increase in inguinal tension force of 4.1, 0.5 N. The upright position (20, 0.7 mm Hg) and the large pneumoperitoneum (25 mm Hg) produced similar values (4.7, 0.8 N and 3.7, 0.4 N, respectively), whereas the small pneumoperitoneum (10 mm Hg) and the electrical stimulation of muscles of the abdominal wall (4.4, 0.1 mm Hg) resulted in distinctly smaller changes (1.1, 0.2 N and 0.7, 0.1 N, respectively). Conclusions: The amount of tension on the simulated Shouldice repair depended largely on the increase in intra-abdominal pressure. Compared with the force required to disrupt the normal inguinal canal (68.6 N) the inguinal load seems to be negligibly low. This finding strengthens the modern recommendation to allow only a short convalescence after Shouldice hernia repair.