There are four stages of wound healing. This systematic process moves in a linear direction. The four stages of wound healing are: hemostasis, inflammation, proliferation, and maturation. It is imperative to remember that wound healing is not linear. It is possible for a patient to move forward or backward through the wound healing phases due to intrinsic and extrinsic forces.

Four Stages of Wound Healing

1. Hemostasis – Hemostasis starts within the first 15 minutes of an injury that extends through the epidermis into the dermis. Capillaries provide blood supply in the dermis layer of skin structure. When an injury occurs to the vessels, this begins coagulation activation. Hemostasis is a natural wound healing process by clotting. Platelet aggregation and activation create the clot formation. Platelets stick together, creating a seal for the blood vessel wall. Coagulation reinforces the platelet seal with fibrinous threads that bind together. This process is followed by fibrinolysis or clot breakdown, which releases growth factors. Vasoconstriction also furthers the process. Hemostasis is the body's normal response to tissue injury and actually initiates the wound healing cascade.^1-3

2. Inflammatory – (1 to 5 days) During the inflammation phase you may see "normal" physiological changes, such as of erythema, warmth, pain, and localized edema. Blood vessels leak transudate that is made of water, salt, and protein. As the fluid builds up, this allows the healing and repair cells to move into the wound bed. The warmth, pain, swelling, and redness that presents in this phase is due to the white blood cells, growth factors, nutrients, and enzymes. This is where cell growth and activation, as well as re-epithelialization occur. If the inflammatory phase becomes prolonged, the injury becomes a chronic wound.^1,2

3. Proliferative – (5 to 25 days) This phase can only take place in a full thickness wound. This would include a Stage 3 and 4 pressure injury/ulcer. The wound contracts as new tissues made up of collagen and extracellular matrix rebuild. Granulation tissue formation occurs in the proliferative phase. Healthy granulation is pink or red in color, with an uneven mounded texture. These mounds are capillary loops or granulation buds. Dark dusky granulation is a sign of ischemia, poor perfusion, and or infection. The proliferative phase will reach completion when myofibroblasts help contract the wound, and epithelial cells start resurfacing across the wound bed.^1,2

4. Maturation – (21 days to 24 months) This is the final phase of full thickness wounds for the healing cascade. You may also see it referred to as the "remodeling" phase. Collagen continues to be remodeled until wound closure. Collagen also reduces scar tissue and strengthens the wound tissue. However, scar tissue tensile strength will only reach 80%, compared to the original tissue.^1,2

Conclusion

The wound healing process is systematic and complex. The process of healing can be interrupted easily due to intrinsic and extrinsic factors. Extrinsic factors affecting wound healing include: smoking, mechanical stress, moisture, infection, and chemical stress. Intrinsic factors that directly affect the performance of healing are: multiple comorbidities, increased age, obesity, nutritional status, and health status.⁴ It is important to have a strong understanding of the skin structure, phases of wound healing, wound types, and identifying risk factors for delayed healing. Every consideration plays a key role in comprehensive wound care management. Understanding the systematic process of how a wound heals enables us as clinicians to apply the most appropriate treatment and management to support the wound healing process.

References

1. Stedman TL. Definition of "wound". In: Stedman's Medical Dictionary. Philadelphia, PA: Lippincott Williams & Wilkins; 2011.

2. Baranoski S, Ayello EA, Langamo D. Acute and chronic wound healing. In: Wound Care Essentials: Practice Principles, 4th ed. Philadelphia, PA: Wolters Kluwer Publishing; 2016; 61-78.

3. Chapin, J.C. & Hajjar, K.A. (2015). Fibrinolysis and the control of blood coagulation. Blood Reviews, 29(1), 17-24. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4314363/

4. Thomas hess C. Checklist for factors affecting wound healing. Adv Skin Wound Care. 2011;24(4):192. Available at: https://journals.lww.com/aswcjournal/Fulltext/2011/04000/Checklist_for_…. Accessed on April 16, 2018.