Wound Healing

Wound -

Definition   

  • A wound is a break in the integrity of the skin or tissues often, which may be associated with disruption of the structure and function.
  • A wound is defined as a separation or discontinuity of the skin, tissue, mucous membrane caused by physical, chemical or biological insult

Classification of Wound

1. Type of Wound

  • Clean incised-An incision in which no inflammation is encountered in a surgical procedure, without a break in sterile technique.
  • Lacerated-A laceration is an irregular cut in the skin caused by a sharp object. an abrasion, none of the skin is missing.
  • Bruising and Contusion-Bruises and contusions are skin discolorations that happen due to an injury to capillaries under the surface of your skin 
  • Hematoma-A hematoma is a collection of blood outside of the blood vessels, often due to injury or trauma.
  • Puncture wound-A puncture wound is a small hole in the skin caused by a sharp object.
  • Abrasion-An abrasion is a wound where your skin rubs off due to friction.
  • Crush Injury-A crush injury is when a body part is squeezed between two heavy objects.
  • Injury to bone and Joint
  • Injury to nerve
  • Injury to arteries and veins
  • Penetrating wound-Penetrating trauma is an injury caused by a foreign object piercing the skin, resulting in damage to underlying structures and an open wound.

2. Thickness of Wound

  • Superficial wound-Involving only epidermis and dermal papillae. 
  • Partial wound-Partial thickness wound with skin loss up to deep dermis with only deepest part of the dermis, hair follicle shafts and sweat glands are left behind.
  • Full thickness-Full thickness wound with loss of entire skin and subcutaneous tissue causing spacing out of the skin edges.
  • Deep wound- Deep wounds are the one extending deeper, across deep fascia into muscles or deeper structures.
  • Complicated wound-Complicated wounds are one associated with injury to vessels or nerves
  • Penetrating wound-Penetrating wounds are one which penetrates into either natural cavities or organs.

3. Surgical Wound

  • Clean wound-These types of wounds are not infected, do not exhibit any signs of inflammation, and are typically closed. If drainage is required, a closed draining approach is recommended. It is worth noting that Class 1 wounds do not involve the respiratory, alimentary, genital, or urinary tracts. Examples of clean wounds include an inguinal hernia repair or a thyroidectomy. 
  • Clean contaminated wound-Means they have a low level of contamination. These types of wounds involve entry into the respiratory, alimentary, genital, or urinary tracts but only under controlled circumstances.
  • Contaminated wound- An incision undertaken during an operation in which there is a major break in sterile technique or gross spillage from the gastrointestinal tract, or an incision in which acute, non-purulent inflammation is encountered.
  • Dirty infected wound-These injuries usually occur from inadequate treatment of traumatic wounds, gross purulence, and evident infections.

Wound healing-

 Would healing is the body's responses to injury in an attempt to restore normal structure and function.

Components of Wound Healing

There are two major components of Wound healing-

  1. Regeneration-Regeneration means healing occurs with replacement of lost cell and tissues with same type of cells or tissues. It takes place by proliferation of parenchymal cells and results in complete restoration of original tissue.
  2. Repair-Repair means healing occurs with replacement of lost cells by connective tissues. In repair tissues donot return to their normal form and functioning. Repair is a more complex process than regeneration

Most injuries heal by connective tissue repair and usually result in scar formation.

Repair healing occurs by-

  1. Primary intention
  2. Secondary intention
  3. Tertiary intention

1. Primary Intention-

Repair by primary intention occurs when wound margins are neatly approximated like surgical cut or incision.

This process includes three phases-

A. Initial Phase (Inflammatory Phase)- 

  1. The initial phase lasts for 3-5 days.
  2. In this phase wound area fills with blood and blood clots form.
  3. An acute inflammatory reaction occurs with migration of leukocytes (WBCS)
  4. Accumulation of fibrin clots, erythrocytes, neutrophils and other debris.
  5. Macrophages ingest and digest cellular debris, RBCs and fibrin fragments. Macrophages and neutrophils help digest fibrin.
  6. Wound debris removed and fibrin clot acts as meshwork that facilitates capillary growth and migration of epithelial cells.

B. Granulation Phase (Proliferation phase)-

It is the secondary phase of primary intention and lasts from 5 days to 3 weeks. It includes proliferation of fibroblasts (immature connective tissues cells that secrete collagen at healing site), capillary sprouts (angioblasts), Various type of WBCs and exudates, loose and semifluid substance.

  1. The fibroblasts release collagen at healing site that organized and matured to form fibrous or scar tissue.
  2. The wound is pink and vascular due to formation of new blood capillaries.
  3. Wound edges begins to regenerate by re- epithelization.

C. Maturation phase and Scar Contraction- This phase begins 7 days after injury and continues for several months or years. It includes remodeling of collagen and strengthening of scar. A mature scar is formed that is avascular, pale and may be more painful than granulation phase.

 

2. Secondary Intention-

  1. The tramatic or ulcerated wounds, infected wounds with large amount of exudates and wide irregular - wound margin with extensive tissue loss are healed by secondary intention.
  2. The inflammatory reaction may be greater than primary intention. So the primary incision is reopened, wound is cleaned and debris are removed and healing by secondary intention takes place.
  3. In secondary intention healing and granulation take place from the edges inward and from the bottom of the wound upward until the defect is filled. There is more granulation tissue and a much larger scar formation.

3. Tertiary Intention-

  1. Healing by tertiary intention occurs with delayed wound suturing in which two layers of granulation tissues are sutured together.
  2. It is usually seen when contaminated wound is left open and sutured after complete elimination of infection.
  3. It also occurs when the primary wound becomes infected, is opened, allowed to granulated and then sutured.
  4. It is usually result in larger and deeper scar than primary or secondary intention.

Different  Between the  first and second Intention of  Healing 

Features Primary Secondary
Cleanliness Clean Not Clean
Infection Not infected  Infected
Margins Surgically clean Irregular
Sutures Used Not used
Healing Small granulation tissue Large granulation tissue
Outcome Linearscar Irregular wound
Complication Not frequent Frequent

 

Factor Affectng Wound Healing 

A.  Local factors

  1. Infection
  2. Presence of necrotic tissue and foreign body
  3. Poor blood supply
  4. Venous or lymph stasis
  5. Tissue tension
  6. Hematoma
  7. Large defect or poor apposition
  8.  Recurrent trauma
  9. X-ray irradiated area
  10. Site of wound, eg.wound over the joints and back has poor healing
  11. Underlying diseases like osteomyelitis and malignancy

B. General factors- 

  1. Age, obesity,smoking
  2. Malnutrition, zinc, copper
  3. Vitamin deficiency (vit C, vit A) iv. Anemia
  4. Malignancy
  5. Jaundice
  6. Diabetes
  7. HIV and immunosupressive diseases
  8. Steroids and cytotoxic drugs

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