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The miraculous process of wound healing: Do you know what the amazing stages are?
A wound is any disruption or injury to biological tissue, which may be the skin, mucous membranes, or internal organs. Wounds may occur suddenly from direct trauma (eg, mechanical, thermal, or chemical) or gradually from underlying disease processes (eg, diabetes, venous/arterial insufficiency, or immune disorders). The appearance of wounds varies greatly depending on factors such as the location of the wound, the mechanism of injury, the depth of the injury, and the sterility of the wound. Strategies for treating wounds will also vary depending on the classification of the wound, so wounds must be fully evaluated by a medical professional in order to be managed appropriately. According to normal physiology, all wounds undergo a series of steps, known as the wound healing process, which includes hemostasis, inflammation, proliferation, and tissue remodeling. Factors such as age, tissue oxygenation, stress, underlying medical conditions, and certain medications can affect the rate at which wounds heal.
The wound healing process consists of four important stages: hemostasis, inflammation, proliferation and tissue remodeling.
Wound classification
Wounds can be broadly divided into acute wounds and chronic wounds, based on the time since injury and the healing process. Both types of wounds can be further categorized based on the cause of the injury, the severity/depth of the wound, and the sterility of the wound bed. Multiple classification systems have been developed to describe wounds and guide their management, including the CDC's surgical wound classification, the International Red Cross wound classification, the Tscherne classification, the Gustilo-Anderson open fracture classification, and the AO soft tissue grading system.
Acute wounds
Acute wounds are those resulting from direct trauma and progress through the four stages of healing along an expected timeline. The first phase is a hemostatic phase that lasts from a few minutes to a few hours, followed by an inflammatory phase that usually lasts 1 to 3 days. Hyperplasia is the third stage of wound healing and lasts from a few days to a month. The last and final repair/scarring phase usually lasts 12 months but may last up to 2 years after the initial injury. Acute wounds can be further divided into open and closed wounds.
Open wounds
An open wound is one where the integrity of the skin is disrupted, exposing the underlying tissue. Types of open wounds include:
- Incisions: Inflicted by a clean, sharp object such as a knife, razor, or broken glass.
- Lavage: An irregular tear caused by a blunt object.
- Abrasion injuries are superficial wounds in which the top layer of skin (epidermis) is scraped away.
- Avulsion: An injury in which a body structure is forcibly separated, similar to an amputation.
- Punch wound: A wound caused by an object piercing the skin.
- Penetrating injury: A wound caused by an object entering the skin and then exiting again.
- Gunshot wound: A penetrating wound caused by a bullet or similar projectile.
Closed wounds
A closed wound is one in which the underlying tissue is damaged but the epidermis remains intact.
- Hematoma: Damage to a blood vessel causing blood to collect under the skin.
- Contusion: Damage to the skin caused by a strong force.
Chronic wounds
Any wound that is interrupted or delayed at any stage in the normal wound healing process is considered a chronic wound. These are generally caused by an underlying medical condition, such as diabetes or venous/arterial insufficiency. Chronic wounds are often caused by a disruption in the inflammatory phase, but errors at any stage can lead to chronic wounds. Generally speaking, wounds that last more than three months are considered chronic.
Diabetes, venous/arterial insufficiency and immune system disorders are the most common causes of chronic wounds.
Wound sterility
Wound sterility is a key consideration when assessing a wound. The Centers for Disease Control and Prevention (CDC) surgical wound classification system in the United States is primarily used to assess the sterility of wounds, particularly in the surgical setting. This classification system divides wounds into four categories, each with its own risk of postoperative infection:
- Category 1 – Clean wounds: Wounds that are not infected and have no signs of inflammation.
- Category 2 – Clean Contaminated Wounds: Wounds with low levels of contamination.
- Category 3 – Contaminated Wounds: Open, accidental wounds resulting from trauma.
- Category 4 – Dirty/Infected Wounds: Wounds with clinical evidence of infection.
Overall, the healing process of wounds is critical regardless of their type. Wound healing can only be promoted if it is correctly identified and managed. With the advancement of science and technology, the effectiveness of wound care continues to improve and promotes the patient's recovery process. For such a complex wound healing process, do we truly understand every stage of treatment and the biological mechanisms behind it?
