**4. Chronic wound**

Chronic wounds do not follow the timely fashion of wound healing. Burns are included in chronic wounds as they take a long duration to heal than acute wounds. A large variety of surgically induced wounds and traumatic wounds are considered as chronic wounds by surgeons, as they heal unexpectedly slow. These chronic wounds

*Minimally Invasive Microneedle: A Novel Approach for Drug Delivery System and Infected… DOI: http://dx.doi.org/10.5772/intechopen.105771*

**Figure 7.** *A picture of the inflammatory phase indicating the inflammation and the action of fibrin and phagocyte [10].*

**Figure 8.** *Graphical representation of four stages of wound healing and their mutual relation is depicted in the figure above [11].*

are also considered as vascularly compromised or infected. Chronic wounds also include the entire category of skin ulcers [14].

Despite good wound management, chronic wounds remain intractable, and they fail to follow the orderly phases of healing. Chronic wounds are detained in a selfperpetuating inflammatory stage. There are a high number of factors that delay wound healing, such as vascular insufficiency, chronic disease, malnutrition, diabetes, and aging. It is also affected by local factors, such as infection, edema, and pressure [15]. The wound gets locked in a prolonged and heightened inflammatory state due to the subsequent tissue damage, which is characterized by reactive oxygen species (ROS) and destructive enzymes perpetuating the cycle associated with neutrophil infiltration. If the primary noxious factor is eliminated, many chronic wounds can be effectively healed [16].

**Figure 9.** *A diagrammatic representation of the remodeling phase and the process involved in maturation or remodeling [13].*

Patients with chronic wounds suffer the loss of function, financial costs, pain, and infections due to nonhealing ulcers, leading to sepsis or amputations. Diabetes, obesity, and the aging population are some of the high-profile issues that give rise to chronic wounds. In most parts of the world, these health issues are on the rise, and with this, the occurrence of diabetic, venous, and nonhealing pressure ulcers also increases. Unfortunately, the appropriate care and education about chronic wounds are lacking. The causes of chronic wounds overshadow their significance, and also, their costs are poorly documented. However, the quality of life of around 40 million people is impacted adversely and persists as a silent epidemic [17].

There are three main categories of chronic wounds: diabetic ulcers, pressure ulcers, and venous ulcers. There exists a fourth small group secondary to arterial ischemia [14].

#### **4.1 Venous ulcers**

Venous stasis ulcers affect around 1–2% of the adult population, primarily women and the elderly. They occur mainly in the lower limb and account for more than half. Venous hypertension and congestion are mainly responsible for venous ulcers caused due to venous thrombosis or valvular incompetence [18]. The blood vessel permeability is increased due to back pressure, which leads to leakage of red blood cells and macromolecules into the perivascular space. These then act as chemoattractants for leukocyte infiltration. Inflammatory processes associated with reperfusion exacerbate the injury, and leg elevation restores the effective loss of circulation. Venous ulcers

*Minimally Invasive Microneedle: A Novel Approach for Drug Delivery System and Infected… DOI: http://dx.doi.org/10.5772/intechopen.105771*

#### **Figure 10.**

*Various stages of venous ulcers: from skin redness, inflammation of the subcutaneous tissue in the area of the lower leg progresses to formation of wound on the surface [19].*

commonly occur in the medial malleolus. They tend to be shallower and more prominent and are irregular with ill-defined margins [19]. **Figure 10** depicts the various stages involved in the formation of venous ulcers.
