Chronic wounds

The four stages of wound healing

  • Hemostasis – It is a process to stop bleeding. The main polymer in this phase is fibrin, which forms scaffold for immune cells migrating into the wound.
  • Inflammation – In this phase, the immune cells activate and prevent the infection.
  • Proliferation – The fibroblasts proliferate and produce extracellular matrix, which allows migration of keratinocytes that cover the wound.
  • Remodeling – In the last phase of wound healing, the scar forms.1


If the physiological wound healing is not completed (typically stays in the inflammation phase), chronic wounds and ulcers occur and require long-term health care.

Fig. 2: Four stages of wound healing on the time scale. Adopted from ref. 1

Chronic wounds and ulcers

The main characteristics of chronic wounds are continuing inflammation, impaired blood vessels formation, and long regeneration of the skin tissue. Leg ulcers, diabetic ulcers, and bedsores are the most common chronic skin injuries.


Diabetic ulcers

Diabetic ulcers result from several problems of diabetic patients, mainly caused by neuropathy.2


Leg ulcers

Venous leg ulcers form probably due to high permeability of veins for molecules negatively regulating skin regeneration.3 Arterial leg ulcers are formed due to skin tissue ischemia developed from high blood pressure or atherosclerosis.


Bedsores (pressure ulcers)

Bedsores are formed by long-term pressure on the skin of bedridden patients. Very dangerous are sacral pressure ulcers that are prone to fecal contamination.4 

Epidemiology of chronic wounds

The global comprehensive data on chronic wound prevalence is missing. There is not a sharp line between acute and chronic wounds, many chronic wounds are not treated in medical institutes, and much of them are not reported. However, the high cost of chronic wound treatment raises the need for representative data. It is estimated that chronic wound treatment in developed countries costs  13 % of the health care budget.5 Meta-analysis of ulcers prevalence in developed countries in years 2000–2017 estimates prevalence 1.67 patients per 1000 citizens of average age 70–80 years.6

There are approximately 55 million patients with diabetes, 8 million of them are susceptible to diabetic ulcers development, which leads to 450 000 amputations of legs every year with costs 2–2.5 billion Euro.7 USA report more than 6.5 million patients with chronic wounds with 25 billion USD yearly treatment costs. Data from developing countries are completely missing.

Early and effective treatment can improve quality of life of patients and cut the treatment costs.5





Explanatory note


1 Las Heras, K., M. Igartua, E. Santos-Vizcaino and R. M. Hernandez. Chronic wounds: Current status, available strategies and emerging therapeutic solutions. Journal of Controlled Release. 2020, 328: 532-550. doi:

2 Jeffcoate, W. J. and K. G. Harding. Diabetic foot ulcers. The Lancet. 2003, 361(9368): 1545-1551. doi:

3 Etufugh, C. N. and T. J. Phillips. Venous ulcers. Clinics in Dermatology. 2007, 25(1): 121-130. doi:

4 Deutsch, M. C., M. D. Edwards and P. S. Myers. Wound dressings. British Journal of Hospital Medicine. 2017, 78(7): C103-C109. doi: 10.12968/hmed.2017.78.7.C103.

5 Olsson, M., K. Järbrink, U. Divakar, et al. The humanistic and economic burden of chronic wounds: A systematic review. Wound Repair and Regeneration. 2019, 27(1): 114-125. doi:

6 Martinengo, L., M. Olsson, R. Bajpai, et al. Prevalence of chronic wounds in the general population: systematic review and meta-analysis of observational studies. Annals of Epidemiology. 2019, 29: 8-15. doi:

7 Homaeigohar, S. and A. R. Boccaccini. Antibacterial biohybrid nanofibers for wound dressings. Acta Biomaterialia. 2020, 107: 25-49. doi: