Wound healing

With wound healing is called the closing of a wound by restoring the damaged body tissue by newly formed connective tissue in connection with epithelialization (overgrowth of epithelial cells). It is a natural process that can be supported therapeutically and with wound dressings . An injury in which wound healing is delayed or stopped progressing becomes a chronic wound .

The article Wound deals with the process of wound healing after a wound has been wound.

Abrasion on hand
Days after injury (approx.)
0	3	17th	30th

Deep wound on the shin with stitches - healing process over five weeks

course

The term wound healing describes a natural biological process and summarizes the processes that lead to the merging of separated tissue and the restoration of destroyed tissue. These processes start immediately after the wound has formed, as has been demonstrated with enzyme histochemical methods. The platelets come to the damaged area and try to close it. In rare cases, a scab develops through exudation (fluid secretion), which also triggers the itching often associated with wound healing .

It is only up to the doctor to improve the conditions to alleviate discomfort (wound pain), to prevent complications or infections, to prevent delays and to make the cosmetic result as optimal as possible. There is not yet any real acceleration of wound healing, but the dry or moist wound environment, depending on the type of wound, is advantageous. The goal of healing is a complete restoration ( restitutio ad integrum ), both functional and cosmetic, but which can rarely be achieved in full. Since tetanus and sepsis (blood poisoning) could develop, special preventive vaccinations are essential. If these are missing, they should be set immediately. A wound caused by an accident should be freed of germs using antisepsis (disinfection), and foreign bodies are also an obstacle to healing. Large open wounds must either be stapled, sutured, or taped. Often a visible scar remains .

When dressing changes are required or recommended no earlier than eight hours after the initial application , doctors or nurses observe the healing progress, clean the wound area and the wound area and protect the wound with a new artificial covering. If wounds are non-irritating and physically closed, they can heal completely open and accelerated by the supply of oxygen.

Phases

A distinction is made between several phases of wound healing that overlap one after the other. This classification is not uniform and not uncontested; it is based on morphological guiding criteria and its characteristic effects are visible to the naked eye in secondary healing wounds. The delimitation of the phases of wound healing from one another differs depending on the source and is arbitrary:

• Latency phase , is sometimes not mentioned separately and / or combined with the subsequent wound healing phase
• Exudative phase , is also known as the inflammation, inflammation or cleaning phase
• Resorptive phase , is sometimes not listed separately, but combined with the previous or subsequent wound healing phase
• Proliferative phase or granulation phase
• Reparative phase or epithelialization or regeneration phase

It can also be divided into three phases:

• Latency phase (1st to 3rd day)
• Proliferation phase (4th to 7th day)
• Reparation phase (from the 8th day)

Latency phase

This phase is not generally included in every breakdown of the various wound healing phases. The starting point of every wound healing is a disturbance of the blood flow through capillary injuries . The initial bleeding initiates blood clotting , the destroyed blood vessel is closed by a clot (blood clot). Now the latency phase, sometimes referred to as a separate phase, begins (from the Latin word for "hidden"; also called the resting phase), since apparently no further reactions that are visible macroscopically and microscopically occur. This phase is assigned to the "exudation phase" in many classification schemes, as it is usually short and difficult to define.

Exudation phase

The name comes from the Latin term exudate - leaking liquid. This process is also known as the cleansing, inflammation or inflammation phase. Due to the destruction of the tissue during the formation of the wound, the destroyed blood vessels initially bleed violently. This will help flush foreign matter out of the wound. A short time later, however, the injured vessels constrict and the blood flow decreases. This process is called vasoconstriction and takes about five to ten minutes . The vasoconstriction is followed by an expansion of the blood vessels, the so-called vasodilation . The increasing blood flow leads to reddening and an increase in skin temperature in the wound area. At the same time, the permeability of the capillary walls increases , so that more blood cells find their way into the wound area. In addition, there is lymph that leaks from the damaged lymph vessels. The increase in fluid in the tissue near the wound causes swelling called wound edema . As the wound exudate begins to escape, residues of the tissue destruction that has taken place, such as cell debris, but also foreign bodies, as well as germs and pathogens, are "washed out" of the wound. This phase can last up to four days and overlap with the following wound healing phase by a few days. In the exudation phase, the cells and hormones of the immune system are significantly involved, not only to kill bacteria or viruses that have entered, but also to stimulate healing itself.

Resorptive phase

The blood clots that close the vessels consist mainly of platelets , which, due to their surface structure, bond with one another and use chemical signals to guide further blood platelets into the wound area. Next, a network of fibrin fibers is formed . This fibrin network, initiated during clot formation, enables the edges of the wound to be glued together. Clear wound exudate, which consists essentially of blood serum and lymph, is interspersed with inflammatory cells. In clean conditions, this phase should not last longer than one to three days. During this phase, cytokinesis (cell division) increases in the wound area. Monocytes mature into macrophages in the wound area , which clear away cell debris and plug. Fibroblasts , which develop from immigrated, but also from local connective tissue cells in the wound edge and multiply through cell division, perform the actual construction work in the following phase. A moist wound environment is required for this and is modeled or supported by modern wound dressings .

Granulation phase or proliferative phase

From the wound edges (induced by a fibroblast proliferation caused by fibronectin and other proteases) collagen fibers build up along the previously formed fibrin network and form new connective tissue . Other cells are stored in it. The result is granular granulation tissue that fills the wound from below and gradually contracts. This will close the wound further. Through proliferation (Latin for 'formation, emergence') of new connective tissue, the wound defect is increasingly filled in this way. Synonym for this is: granulation phase . The visible granulation tissue is named for this (Latin granulum  = 'grain'; the filling tissue looks coarse-grained). Hand in hand with the cell-rich filling of a wound defect is the breakdown of the fibrin network ( fibrinolysis ) by plasmin. At the same time, the vascular abundance (lat. Vascularization ) increases due to the sprouting hair vessels . The fibroblasts produce hexosamine-containing acidic muco- polysaccharides as topsoil (extracellular basic substance of connective tissue) and, via intracellular precursors, the extracellular collagenous connective tissue fibers . The timing is very complex and is subject to the influence of numerous growth factors ( cytokines ). The granulation tissue can only develop in a timely manner if there is no general and local malnutrition (no insufficient blood flow) and no metabolic diseases hinder growth. In the case of very small wounds, this tissue can develop after just a few hours (after needle stick injuries within a few minutes). The granulation phase usually starts between the second and fourth day and lasts until the 14th day of wound healing. It takes place over many days at the same time as the subsequent wound healing phase. Between the sixth and tenth day, the collagen fibers begin to mature.

Regeneration phase, reparation phase or reparative phase

In the regeneration phase, the surface wound is closed by epithelialization (after epithelium - covering tissue; → epidermis ). The diameter of a well granulated wound closes to one third only by shrinkage to two-thirds by new formation ( cell division ) of surface cells and cell migration on the "slideway" liquefied fibrin from the edge of the wound for wound centers. The prerequisite for the reparative phase to proceed without complications is a sufficiently moist and warm wound environment that favors the migration of fresh cells. The drying out of the wound bed can lead to wound healing disorders. The filling connective tissue (granulation tissue) increasingly forms collagen fibers, which means that the restoration of all skin layers is almost complete. In the end, a new layer of skin is formed on the surface of the wound through the so-called epithelialization . As a result of all processes, a scar is created . It towers above healthy skin first and sinks in over time by tightening the connective tissue. The scar tissue is clearly different from the surrounding skin, as it does not contain any hair or sweat glands and also no melanocytes (pigment cells). Since no elastic fibers are formed, the originally vascularized scar tissue ("red scar") as connective tissue with little capillary and cell ("white scar") has no elasticity and is inevitably inferior, which is why a minimal scar is sought in therapy planning .

Remodeling

Wound healing is followed by a longer phase of remodeling and expansion processes in which the tissue structure continues to change. These processes are referred to with the terms "remodeling" or "maturation". Some classifications prefer a special designation for the further functional adaptation of the scar tissue (maturation) to the locally different requirements. Others consider this process of regeneration to be part of the process. The further increase in the tear strength of the scar tissue depends on the cross-linking, solidification and alignment of the collagen fibers. The water content of the tissue decreases, the scar that initially protrudes slightly above the skin level regularly shrinks below the skin level. The number of vessels in the scar tissue also decreases. The originally fresh red stigma turns white. This process takes one to two years.

Forms of wound healing

Epithelial wound healing takes place in superficial wounds in which only the epidermis is affected - for example in the case of abrasions - and is completed without scars after a few days. Epithelial wound healing is a regenerative process, while the other two types of wound healing are repaired.

Primary wound healing: Primarily healing (p. P. = Sanatio per primam intentionem) wounds are defined as wounds whose edges close flush without infection , e.g. B. also surgical wounds that have been sutured.

Secondary wound healing: Secondary healing (p. S. = Sanatio per secundam intentionem) wounds are those with a tissue defect. These wounds are infected with bacteria ( colonized with bacteria ). The type of germ can be identified by a wound smear and the effectiveness of antibiotics can also be predicted using an antibiotic or resistogram.

This subdivision is important when assessing the surgical procedures. Under comparable conditions, i. H. same operation and similar patient population, the higher number of secondary healed wounds is a negative sign (questionable surgical sterility, nursing wound care, etc.).

Complications

Various factors can have a negative impact on the healing process (e.g. as a wound healing disorder ) or the formation of scars. The result is large, deforming or insufficient scars or chronic wounds .

Disruptive factors of a general nature

• In the case of large wounds , the increased exudation leads to extensive granulation tissue and thus has a negative impact on healing (healing by secondary intention ).
• Unilateral wound storage can decubitus or leg ulcers cause, which is counterproductive for healing.
• Early exposure can lead to wound dehiscence or a hernia .
• The contractile properties of the myofibroblasts lead to a reduction in the volume of the scar and thus possibly to scar contractures .
• Infections of the wound favor the development of granulation tissue and thus excessive scarring.

Even with optimal care, there is sometimes an excessive increase in connective tissue ( keloid ) . The reason for this is unknown.

Systemic diseases

Certain systemic diseases can lead to complications.

• Fibroblasts are dependent on an oxygen partial pressure of at least 15 mmHg. As a result, diseases that cause a reduced blood and thus oxygen supply have a negative effect on healing (especially arterial occlusive disease , arteriosclerosis )
• Diabetes mellitus causes poor wound healing due to two factors: poor blood flow due to vascular changes on the one hand and a reduced body's own infection control on the other.
• Glucocorticoids inhibit wound healing via phospholipase A2.
• Changes in the blood count in the sense of granulocytopenia or congenital defects in chemotaxis or phagocytosis also result in reduced wound healing.

Chronic or non-healing wounds

→ Main article : Chronic wound

In some wounds, the interaction of degrading (= catabolic ) and constructive (= anabolic ) reactions shifts to the disadvantage of the constructive processes. The disturbed healing process then usually stagnates in the first phase of wound healing, the inflammation phase . Such wounds are known as chronic wounds . The definition of this term is internationally inconsistent. For example, there is disagreement about how long a wound should last to be called a chronic wound. There is also no uniform definition of whether the onset of healing or the signs of healing cancels this status. The Association of Initiative Chronic Wounds defines a period of eight weeks as a characteristic of a chronic wound, but at the same time emphasizes that certain wounds, such as the venous leg ulcer , the pressure ulcer or diabetic foot ulcer are to be regarded as chronic wounds from the time they develop .

Tissue management

In the case of chronic wounds, the inflammatory phase continues, which delays or even blocks the regeneration phase. The methods of regenerative medicine (tissue engineering) aim to achieve wound closure in these cases too. For this purpose, either the body's own cells or those from external donors are used for the production of skin equivalents. So z. B. the keratinocytes , cells of the epidermis, reproduced in a three to four week process and then applied directly or by means of a carrier to the wound. The duration of the subsequent healing depends on the general conditions.

Other complications

Tissue that has been damaged by radiation - for example, by radiation therapy  - has a lower ability to heal.

Active measures

Adult stem cell therapy is being investigated as an active measure to promote wound healing .

With the help of modern wound management, wounds heal faster.

For calcium carbonate , a promotion of wound healing in dentistry given.

See also

• wound
• Wound pad
• Moist wound treatment
• Dry wound treatment

literature

• Kerstin Protz: "Modern wound care. Practical knowledge, standards and documentation" , Elsevier Verlag, 8th revised edition, Munich 2016, ISBN 978-3-437-27885-3
• Anette Vasel-Biergans, Wiltrud Probst: wound care for nursing. A practice book . 2nd revised edition. Scientific Publishing Company Stuttgart, Stuttgart 2011, ISBN 978-3-8047-2798-4
• GMS hospital hygiene interdisciplinary. Journal of the German Society for Hospital Hygiene (DGKH). Volume 1 (2006): The infected problem wound. [with 33 contributions]. The infected problem wound
• P. Kujath , A. Michelsen: Wounds - from physiology to dressing . In: Deutsches Ärzteblatt , 2008, 105 (13), pp. 239–248.
• Klaus-Jürgen Bauknecht, Joachim Boese-Landgraf: Wounds, wound healing, wound healing disorders, wound treatment, tetanus prophylaxis. In: Rudolf Häring, Hans Zilch (Hrsg.): Textbook surgery with revision course. (Berlin 1986) 2nd, revised edition. Walter de Gruyter, Berlin / New York 1988, ISBN 3-11-011280-9 , pp. 7-17, here: pp. 10-12 ( wound healing ).
• Klinikverbund Südwest (Ed.): Handbook care of problem wounds . November 2006 ( klinikverbund-suedwest.de [PDF]).

Web links

Wikiquote: Wound  - Quotes

• German Society for Wound Healing and Wound Treatment e. V.
• Chronic Wounds Initiative V.

Individual evidence

1. ↑ ^{a b c d e f} S. Piotek, J. Toutenhahn: Physiology of wound healing . In H. Lippert: Wundatlas . Georg Thieme Verlag, Stuttgart 2006, ISBN 3-13-140832-4 , pp. 28-33
2. ↑ Klaus-Jürgen Bauknecht, Joachim Boese-Landgraf: Wounds, wound healing, wound healing disorders, wound treatment, tetanus prophylaxis. In: Rudolf Häring, Hans Zilch (Hrsg.): Textbook surgery with revision course. (Berlin 1986) 2nd, revised edition. Walter de Gruyter, Berlin / New York 1988, ISBN 3-11-011280-9 , pp. 7-17, here: pp. 11 f. ( Wound healing phases ).
3. ↑ ^{a b} A. Vasel-Biergans, W. Probst: Wound care for care. A practice book . Knowledge Verlagsges. Stuttgart, Stuttgart 2011, pp. 16-22
4. ↑ Klaus-Jürgen Bauknecht, Joachim Boese-Landgraf: Wounds, wound healing, wound healing disorders, wound treatment, tetanus prophylaxis. 1988, p. 12.
5. ↑ Klaus-Jürgen Bauknecht, Joachim Boese-Landgraf: Wounds, wound healing, wound healing disorders, wound treatment, tetanus prophylaxis. 1988, p. 12.
6. ↑ Joachim Dissemond: Eye diagnosis of chronic wounds. About the clinical inspection for diagnosis , 3rd edition, Viavital Verlag, Cologne 2016, ISBN 978-3-934371-55-2 , page 11
7. ↑ Standards of the ICW e. V. for the diagnosis and treatment of chronic wounds . (PDF) In: Wundmanagement , Issue 2, Volume 11, mhp-Verlag 2017, pp. 81–86
8. ↑ W. Vanscheidt, A. Ukat, V. Horak, H. Bruening, J. Hunyadi, R. Pavlicek, M. Emter, A. Hartmann, J. Bende, Th kennel, T. Ermuth, R. Eberhardt. Treatment of recalcitrant venous leg ulcers with autologous keratinocytes in fibrin sealant: A multinational randomized controlled clinical trial . In: Wound Rep Reg , 15, 2007, pp. 308-315.
9. ^ Frank Haubner, Elisabeth Ohmann, Fabian Pohl, Jürgen Strutz, Holger G. Gassner: Wound healing after radiation therapy: Review of the literature . In: Radiation Oncology . tape 7 , 2012, p. 162 , doi : 10.1186 / 1748-717X-7-162 (English).
10. ↑ The hope for adult stem cells. Max Planck Society , February 11, 2008, accessed on March 7, 2019 . 
11. ↑ Cell-based, regenerative medicine. Federal Ministry of Education and Research, accessed on April 10, 2019 . 
12. ^ Stem cells from development to the clinic. Nature , June 15, 2018, accessed April 10, 2019 . 
13. ↑ Actively accelerate wound healing. (PDF) October 20, 2011, accessed April 10, 2019 . 
14. ↑ Thomas Kindermann: Influence of a subgingivally applied calcium hydroxide preparation on the inflammatory reaction in periodontitis and its regenerative / reparative capacity on the periodontal tissue . Ed .: Saarland University. February 2013, p. 34 ( uni-saarland.de ).

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