Page 136 - Prevention and Treatment of Incisional Hernia- New Techniques and Materials

Chapter 6
stoma opening can lead to obstruction while an overly large stoma opening can perhaps incite a higher frequency of PSH. These mechanisms can explain the high incidence of PSH found in general and also in our study. However, with a prevalence of over 37% at 49 months, the IH rate in our population is one of the highest found in the literature (3, 22, 23). Examination of the CT scans showed this number to be even larger - up to 48.3%. This high prevalence can probably be attributed to the presence of a PSH. When looking at the location where the IH occurred, it is striking to see that 55% of the IHs occurred at exactly the same level as the colostomy. For instance, patients with a colostomy at the M3 level (EHS classi cation) developed IH in most cases between 3cm above and 3cm below the umbilicus (M3). It can thus be hypothesized that the mechanical forces during inspiration and expiration change after colostomy creation. The midline incision tends to shift to the contralateral side due to reduced restraining force at the site of the colostomy. This explanation is visualized in Figure 2. The midline shift increases the tensile force on part of the sutures and can thus create direct postoperative separation of wound edges, which is a major predictor of IH (24, 25). The tensiles force and the midline shift will increase further after PSH development, with a further reduction of the restraining force as a result. Another possible explanation is atrophy of the rectus muscles on the colostomy side due to the disruption of nerve innervation during placement of the colostomy. This atrophy can create a weak spot at the level of the colostomy and thus induce IH. In the literature, it is also stated that some patients may be subject to herniosis and thus biologically prone to herniation (26-30). However, in the present study, no other possible symptoms of herniosis were found except the strong association between PSH and IH: Patients with a PSH and/or IH did not have more inguinal, umbilical or other incisional hernias. One can also hypothesize that all patients with a PSH have a form of herniosis in light of the fact that PSH can often be attributed to technical failures. Further research should thus examine both the biological and biomechanical aspects of hernia as the etiology may very well be a combination of the two.
In the present study, we found a di erence in the hernia rates for the two types of surgery performed in our patient group. Surgical site infections have been shown to increase IH rates, which means that the nature of both of these operations could - in principle - contribute to the high incidence of hernias (31, 32). APR and HMP are by de nition potentially contaminated surgeries.
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