Complex wounds pose a significant challenge for many health care providers. These wounds are often multifaceted, making treatment tremendously difficult. They represent a substantial burden on the health care industry, with annual costs in North America alone estimated at $10 billion annually.¹ They often also result in patient discomfort and pain, caregiver frustration, individual economic losses, and diminished quality of life. Complex wounds may be chronic, with one or more of the following factors¹:

• The inability to heal within three months
• The presence of infection
• Compromised viability of superficial tissues, necrosis, or impaired circulation
• Association with systemic disorders

The primary types of complex wounds include diabetic foot ulcers, pressure ulcers, venous insufficiency ulcers, infected wounds, and those related to vasculitis and immunosuppressive therapy that resist healing with simple treatment.¹

Risk Factors for Complex Wounds

Infection

One of the most common challenges in wound healing and the development of complex wounds is the presence of infection. Although bacteria are part of the skin's normal condition and are necessary for overall health, when the bioburden exceeds 10⁵ bacteria per gram of tissue, bacterial biofilm is no longer classified as colonization, but as infection.² The most common biofilm generators are Staphylococcus aureus and Pseudomonas aeruginosa. Conditions such as diabetes, venous insufficiency, malnutrition, malignancies, edema, and repetitive trauma can contribute to the likelihood of increased bioburden that may become an infection.³ The presence of this infection will disrupt the highly complex process of healing by preventing perfusion of the wound bed. Until the infection is treated and resolved, the wound will persist.

Massive Skin Loss or Severe Burns

When large areas of the skin become damaged, the wound is much more challenging to treat. When wounds are small, they may be treated, dressed, and cared for more easily, whereas more extensive cutaneous injuries may require more aggressive total care. This can include hospitalization, the administration of systemic antibiotics, and more involved dressing and topical treatment regimens. Extensive dermal injuries have an increased risk of infection, and in some cases, a skin graft may be necessary.⁴ Similarly, burns that affect over 20% of the total body surface area can result in burn shock, or acute system responses such as increased capillary permeability, increased hydrostatic pressure across the microvasculature, protein and fluid movement from the intravascular space into the interstitial space, increases in systemic vascular resistance, reduced cardiac output, and hypovolemia requiring fluid resuscitation.⁵ Early excision of burn wounds minimizes the risk of infection and reduces mortality, although the complexity of healing and the need for autologous grafting are primarily determined by wound depth.⁶

Chronicity and Comorbidities

Chronic wounds form when other pathological factors come into play, preventing progression along the wound healing continuum. Given the physiological requirements for wound healing, chronicity is common, and underlying diseases frequently add to this, although external factors can also contribute to chronicity. Chronicity can stem from many sources, sometimes several at once, including the following²:

• Those that impact blood supply, such as peripheral vascular disease
• Those that impact the immune system, such as immunosuppression or acquired immunodeficiency
• Metabolic diseases, such as diabetes
• Medications
• Previous local tissue injury, such as those that can occur from radiation therapy or as a result of surgery
• Sustained pressure, changes in temperature, and moisture

Development of Other Wound-Related Conditions

In addition to these factors and comorbidities, the presence of certain other skin, tissue, and bone conditions can increase wound complexity and contribute to increased difficulties in treatment. These include the following⁷:

• Osteomyelitis: Osteomyelitis occurs when an infection moves from the surrounding tissue to the underlying bone. This condition is common for patients with diabetic foot ulcers, and it increases the risk of lower extremity amputation. Depending on severity, treatment recommendations for osteomyelitis include amputation, antibiotics, or a combination of both, which is currently in line with Infectious Diseases Society of America (ISDA) guidelines.⁸
• Necrosis or gangrene: When peripheral vascular disease is present, the decreased blood flow can contribute to occlusion of the blood vessels and can cause ischemia, pain at rest, ulceration, and gangrene. This condition is primarily treated with revascularization, but wounds resulting from ischemia may require antibiotic therapy, debridement, or amputation.
• Periwound dermatitis: Moisture-associated dermatitis, or maceration, refers to damage of the periwound area, but not the wound itself. This can predispose the area to mechanical injuries from pressure, shear, and friction, further delaying wound closure.
• Edema: Periwound edema can slow or even stop healing. It can also be a cause of additional wounds, which increase pain and the risk of infection. In chronic wounds, mild edema may be transient, but it can frequently require compression therapy, extremity elevation, increased activity, and medications, as needed, for fluid overload.
• Hematomas: Hematomas and seromas may be the cause of chronic wounds. They may also form at surgical sites, which can lead to infection and incisional dehiscence.

Conclusion

Complex wounds represent a massive burden on the health care system and the patients affected by them. Early identification of risk factors and a multifactorial treatment plan can improve the ability to treat all of the factors contributing to complex wounds successfully and help to achieve better patient outcomes.

References

1. Tricco AC, Antony J, Vafaei A, et al. Seeking effective interventions to treat complex wounds: An overview of systematic reviews. BMC Med. 2015;13:89.

2. Han G, Ceilley R. Chronic wound healing: A review of current management and treatments. Adv Ther. 2017;34(3):599-610.

3. Dargo F, Gariazzo L, Cioni M, Trave I, Parodi A. The microbiome and its relevance in complex wounds. Eur J Dermatol. 2019;29(1):6-13.

4. Torrens R. Complex wounds: definition, symptoms and treatment. study.com. https://study.com/academy/lesson/complex-wounds-definition-symptoms-tre…. Accessed June 27, 2019.

5. Rowan MP, Cancio LC, Elster EA, et al. Burn wound healing and treatment: review and advancements. Crit Care. 2015;19:243.

6. Singer AJ, Boyce ST. Burn wound healing and tissue engineering. J Burn Care Res. 2018;38(3):e605-e613.

7. WoundSource Practice Accelerator. Complications in chronic wound healing and associated interventions. WoundSource. 2018. https://www.woundsource.com/blog/complications-in-chronic-wound-healing…. Accessed June 27, 2019.

8. Lipsky BA, Berendt AR, Cornia PB, et al. 2012 Infectious Diseases Society of America clinical practice guideline for the diagnosis and treatment of diabetic foot infections.