Tissue viability is crucial in managing all types of wounds, including surgical wounds, traumatic wounds, pressure injuries, lower-extremity ulcers, and skin tears. Accurate assessment and wound diagnosis are important in treating symptoms and understanding the underlying pathophysiology of the wound.¹ Chronic, nonhealing wounds are those that fail to progress through a timely sequence of repair or those that go through the wound healing process without restoring anatomical function or producing functional results. When wound healing is impaired, there are often multiple factors at work.² In these instances, the tissues can become devitalized, wherein a lack of blood supply will result in the tissue becoming nonviable.¹

Wound Tissue

Devitalized tissue is detrimental to healing and typically must be removed to expose viable tissue and promote healing. Removing devitalized, nonviable tissue provides space for granulation and reepithelialization. The four most common types of devitalized tissue are described below.

Necrotic Tissue: This is dead tissue that is no longer able to heal in any capacity. It cannot be restored and must be removed for the wound to heal. Without removal, this tissue acts as a physical barrier to the formation of granulation tissue in the wound bed. Necrotic tissue is also a medium for increased bacterial proliferation, and removing it is essential for managing the wound’s bioburden.³ Necrotic tissue can be black or brown. It can be hard, dry, and leathery or soft and wet. It can be either firmly or loosely attached to the wound bed.⁴ A dark, or even black, appearance normally marks gangrenous necrotic tissue, which can occur in ischemic wounds. Liquefactive necrosis is marked with a liquid-like yellow layer composed of dead leukocytes. This type of necrosis is generally caused by a bacterial, viral, parasitic, or fungal infection.⁵ Necrotic eschars can result from tissue necrosis and death. They are usually black and dry and can be adherent to the wound or raised.⁶ If the eschar is hard, black, and adherent, do not remove it as it is the body’s natural barrier to outside microorganisms.

Slough Tissue: Unlike necrotic tissue, which is caused by a loss of blood supply, slough occurs when a wound gets stuck in the inflammatory phase of healing. It is composed of dead white blood cells, fibrin, cellular debris, and liquefied devitalized tissue. Prolonged inflammation is associated with the continuous cycle of breaking down and remodeling tissue. During this process, matrix metalloproteinase levels increase, degrading proteins and growth factors that promote healing. The number of white blood cells rises and cell death increases, resulting in the accumulation of slough, which provides an environment for bacterial proliferation, increasing inflammation, and wound chronicity. A failure to remove the slough continues to prolong the inflammatory phase and impair healing.⁶ Slough is marked by its color, which can be yellow, tan, gray, green, or brown. It can be stringy and loose or thick and adherent to the wound bed. It is imperative that slough be debrided to kick-start the healing process and allow for the ingrowth of healthy granulation tissue.⁷

Keratotic Tissue: In many wounds, hyperkeratosis occurs, which thickens the epidermis. It can cause a rolled or curled-under appearance around the wound edges, called epibole. When epibole develops, it is often hard and ridged, with a raised or rounded appearance. This effect can be caused by hypoxia in the tissue, infection, or an unhealthy wound bed. Treatment for epibole requires debridement to jump-start the healing process.⁸

Bone and Muscle Tissue: In advanced lesions and severe diabetic foot ulcers (stage 4), debridement may extend deep into the subcutaneous tissue and involve bone and muscle.⁹ Recognizing these tissues, even when healthy, can be difficult. If they are necrotic or devitalized, they will need to be removed. Treating wounds when there is a loss of extracellular matrix combined with exposed bone, tendon, and muscle can be a tremendous clinical challenge. The development of granulation tissue and subsequent reepithelialization over these structures is extremely slow and may not happen at all without employing a flap over the exposed tendons and bone.⁹ Osteonecrosis, or the death of bone tissue, can be incredibly painful, and such tissue often requires removal, with possible bone grafting depending on the site.¹⁰

Conclusion

The proper identification and assessment of devitalized tissue are crucial for deciding which wound care interventions are appropriate. Debridement of nonviable tissue can improve visualization of the wound bed and assessment of its depth. It’s also imperative to correctly identify where the healthy tissue begins, whether it is bone, muscle, tendon, or subcutaneous tissue. Identification of different healthy and unhealthy tissues can also help clinicians understand any other characteristics within the wound bed that need to be addressed to promote healing of the wound.¹

References

1. Young T. Accurate assessment of different wound tissue types. Wound Essentials. 2015;10(1):51-54.

2. de Moya M, Phan HH, Montero P, Stefanidis D, Cahalane MJ. Non-healing wounds. American College of Surgeons Division of Education ACS/ASE Medical Students Core Curriculum. https://www.facs.org/-/media/files/education/core-curriculum/nonhealing…. Accessed March 23, 2021.

3. Swezey L. Necrotic wounds: Overview and treatment options. WoundSource. https://www.woundsource.com/blog/necrotic-wounds-overview-and-treatment…. Published Oct. 7, 2013. Accessed March 23, 2021.

4. Nichols E. Describing a wound: From presentation to healing. Wound Essentials. 2015;10(1):56-61.

5. Astier A. The different types of necrosis and their histological identifications. Medicine & Pharmacy. https://www.andreasastier.com/blog/the-different-types-of-necrosis-and-…. Published June 30, 2020. Accessed March 23, 2021.

6. Milne J. Your guide to desloughing wounds. https://woundcentral.com/images/pdf/Urgo_guide_desloughing_wounds.pdf. Updated 2015. Accessed March 23, 2021.

7. Skilled Wound Care. Tissue types. https://www.skilledwoundcare.com/tissue-types. Accessed March 23, 2021.

8. Wound Care Education Institute. Wound care and epibole: It’s all about the edge. https://blog.wcei.net/wound-care-and-epibole-its-all-about-the-edge. Published May 18, 2017. Accessed March 23, 2021.

9. Simman R, Hermans MHE Managing wounds with exposed bone and tendon with an esterified hyaluronic acid matrix (eHAM): a literature review and personal experience. The Journal of the American College of Clinical Wound Specialists. 2017;9(1-3):1-9.

10. Goodman SB Osteonecrosis. Merck Manual Consumer Version. https://www.merckmanuals.com/home/bone,-joint,-and-muscle-disorders/ost…. Updated June 2020. Accessed April 7, 2021.