Factors Contributing to Formation of Incisional Hernias
Incisional hernias are acquired defects of the abdominal wall as a result of a previous surgical incision. In the United States the majority of abdominal surgeries are performed through an incision made in the center of the abdominal wall that can extend several inches above and below the umbilicus (belly button). These incisions are referred to as “midline” incisions.
There are several techniques that are used to close the abdominal wall and several different suture options. One of the more frequently used techniques is a “running, continuous closure”. A suture is anchored to the top of the incision and the right and left sides of the incision are sewn together toward the bottom. A second suture starting at the bottom of the wound sewn upward until the two sutures meet and are tied together. Many surgeons use a slowly dissolving suture that can provide tissue support for roughly 60 days. Others may use a permanent, non-dissolvable suture.
Despite the differences in techniques and use of various sutures the rate of incisional hernia remains high. The incidence of developing an incisional hernia in the first year after a surgery that requires a midline incision is approximately 10%. The incidence increases in the second and third year after surgery to approximately 20%.
The reason for hernia formation is not completely understood but several factors have been demonstrated to increase the chances of wound failure and the development of incisional hernias. The factors can be divided into two main categories: technical factors and physiologic factors.
The technical factors are generally thought to be the result of tissue ischemia and wound tension. It has long been known that the length of the suture should be a minimum of 4 times the length of the wound to be closed. The size of the “suture bite” and the space in between each suture passed through the tissue play a big role in wound healing. Suture material also plays a significant role in the way wounds heal. Despite the development of new techniques and different sutures that have come to market the rate of hernia formation has been unchanged for many years. This likely stems from the number of patient related issues that portend hernia formation.
It has long been known that obesity leads to increased intra-abdominal pressures. The pressure exhibited on a healing wound causes increased tension and decreased wound healing efficiency. Chronic diseases, particularly diabetes, also interferes with wound healing and increases the odds of developing wound infections. Wound infection after surgery is a major contributor to the development of incisional hernias. Smoking, a modifiable risk factor, is another significant factor in the development of both infection and incisional hernia. There are several other factors that contribute to the development of incisional hernias including: older age, malnutrition, immunosuppression and male gender.