After surgery, wound margins are usually approximated by suturing, metal clips, glue or adhesive patches. These processes hold wound margins closed for a few days. This kind of healing is called “healing by first intention.” However, not all surgical incision are closed using these methods: if there is a risk of infection or there has been a significant loss of tissue so that the margins cannot be joined, the wounds are left open in order to allow them to heal bottom-up. This kind of healing is called “healing by second intention.” This process takes much longer than healing by first intention because the tissues that are missing or that are non-viable need to be replaced by viable cells. The open area is more extended and the consequent inflammatory reaction can become chronic. The healing may involve the formation of an eschar or scab composed of dry plasma and dead cells, and the cells of the surrounding vital tissues (fibroblasts and vascular tokens) migrate towards the center of the wound and form “granulation tissue” that is fragile and bleeds easily. Only in the last phase of healing does “re-epithelisation “occur, which is the growth of the outermost skin layer that sometimes partially retracts the wound.
For example, wounds resulting from the removal of pilonidal and fistulas, burns and other events that cause a loss of substance (such as after trauma), in which grafts and flaps are not indicated, are healed by second intention. Treating these open surgical wounds are challenging because they are large, deep, carry a high risk of infection and can produce a lot of fluid (called exudate), which is difficult to manage. The options available, in addition to absorbent dressings such as those with alginates, include the use of negative pressure therapy, which has become the most widely used form of advanced therapy for various types of wounds. The negative pressure therapy “sucks” the liquid that originates in the wound and collects it in a binder called a “canister.” This action keeps the wound dry and reduces the bacterial count. Some studies indicate that negative pressure therapy can reduce healing time by one-half to one-third compared to traditional dressings.