As discussed above, open full-thickness wounds heal by secondary intention heal by scar tissue formation and wound contraction. When wounded, the human body sets into motion a cascade of processes resulting in new collagen production to fill the open defect wound (full-thickness) in the skin/tissue.
If the skateboarder we talked about earlier (who skinned their knee) is young and healthy (e.g., with adequate tissue perfusion, oxygenation, nutrition, and without serious comorbid conditions), their knee will bleed for a few seconds, while clotting factors and fibrin will start clotting the blood. Chemical signals (cytokines) will be initiated, resulting in localized edema, redness in the area, slight warmth, and pain. The localized pain, edema, warmth, and redness will typically resolve in 3-7 days (inflammatory phase of acute wound healing). If the wound bed is not kept moist, the wound will dry out, and a scab will form.
Next, the body will produce enzymes (matrix metalloproteinases or MMPs) under the scab to lift it, especially at the edges. The wound bed under the scab will be moist to promote cellular communication, proliferation, and movement (Raziyeva et al., 2021). The young skateboarder may pick the scab off, especially if it feels tight or "itchy." However, the scab will become smaller this time as the wound contracts. If all goes as expected, the wound will completely close (re-epithelialize) in a few weeks. As described, this is an example of an acute wound following the expected pathway to healing.
Open wounds (not sutured surgical wounds) that are kept continuously moist heal almost 50% faster than those allowed to dry out and scab over. The skateboarder's scenario demonstrates uncomplicated acute wound healing. The typical needs of acute wounds versus chronic wounds are described below.
The typical need for uncomplicated ACUTE wounds in a healthy individual includes:
- Moisture balance:
- Keeping the wound bed moist
- Keeping the wound covered
In contrast to acute wounds, any wound that does not follow the expected orderly pathway to healing is a chronic wound. Many factors contribute to an acute wound developing into a chronic wound. The factors are the patient's immune function, comorbid conditions, moisture imbalance, poor nutrition, biofilm/excessively high bioburden in the wound, and the presence of necrotic tissue (Sibbald et al., 2021).
Inflammation in chronic wounds typically starts as it does in acute wounds:
|Wounding → Bleeding → Clotting cascade → Release of cytokines → Edema, warmth, redness, pain|
However, unlike acute wounds, in chronic, complex, or recalcitrant wounds, the expected pathway to healing may never progress out of a chronic inflammatory state. Chronic wounds most often get "stalled" or "stuck" in the inflammatory phase of healing, resulting in delayed wound healing and, often, persistent edema, redness, and pain (Maheswary et al., 2021; Sibbald et al., 2021).
One of the main treatment aims in chronic wound management is to try to convert chronic wounds back into acute wounds healing trajectory. However, some wounds may not be healable. Therefore, at the start of a chronic wound assessment, it should be determined how likely the wound is to heal with optimal management. What is the goal of treatment or chronic wounds management? Healing / complete closure? Maintaining the wound/preventing it from worsening or becoming infected? Or palliative care / bothersome symptom management (such as odor, pain, or drainage?). All of the patient's care team and the patient and their family/caregivers should know the main goal of treatment (Sibbald et al., 2021).