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Healing Of Wound
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Introduction
The body response to injury in an attempt to restore normal structure and function.
Involves 2 distinct processes:
Regeneration: healing takes place by proliferation of parenchymal cells and usually results in complete restoration of the original tissues.
Repair: healing takes place by proliferation of connective tissue elements resulting in fibrosis and scarring.
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REPAIR
Repair is the replacement of injured tissue by fibrous tissue.
Two processes are involved in repair:
Granulation tissue formation;
Contraction of wounds.
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4. Granulation Tissue Formation
Th3 phases are observed in the formation of granulation tissue
PHASE OF INFLAMMATION
PHASE OF CLEARANCE
Combination of proteolytic enzymes liberated from neutrophils, autolytic enzymes from dead tissues cells
phagocytic activity of macrophages clear off the necrotic tissue, debris and red blood cells.
PHASE OF INGROWTH OF GRANULATION TISSUE
2 main processes: angiogenesis or neovascularisation, and fibrogenesis
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CONTRACTION OF WOUNDS
Wound starts contracting after 2-3 days and the process is completed by the 14th day.
Reduced by approximately 80% of its original size
This process aids in rapid healing – lesser surface area of the injured tissue has to be replaced
It takes place in following step : Dehydration and formation of myofibroblast (intermediate between fibroblast and muscle cells.
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6. PHASES OF WOUND HEALING
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WOUND HEALING
Healing of skin wounds - classical example of combination of regeneration and repair
It can be accomplished in one of the following two ways:
Healing by First intention (primary union)
Healing by Second intention (secondary union)
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8. Healing by First intention
Healing of a wound which has the following characteristics:
clean and uninfected;
surgically incised;
without much loss of cells and tissue; and
edges of wound are approximated by surgical sutures
The incision causes only focal disruption of epithelial basement membrane continuity and death of a relatively few epithelial and connective tissue cells.
As a result, epithelial regeneration predominates over fibrosis.
A small scar is formed, but there is minimal wound contraction
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9. EVENTS IN PRIMARY UNION
Within 24 hours,
neutrophils are seen at the incision margin, migrating toward the fibrin clot.
Basal cells at the cut edge of the epidermis begin to show increased mitotic activity.
Within 24 to 48 hours
epithelial cells from both edges have begun to migrate and proliferate along the dermis, depositing basement membrane components as they progress.
The cells meet in the midline beneath the surface scab, yielding a thin but continuous epithelial layer
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10. EVENTS IN PRIMARY UNION: By day 3
Neutrophils have been largely replaced by macrophages,
Granulation tissue progressively invades the incision space.
Collagen fibers are now evident at the incision margins, but these are vertically oriented and do not bridge the incision.
Epithelial cell proliferation continues, yielding a thickened epidermal covering layer.
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11. EVENTS IN PRIMARY UNION : Day 5
neovascularization reaches its peak as granulation tissue fills the incisional space.
Collagen fibrils become more abundant and begin to bridge the incision.
The epidermis recovers its normal thickness as differentiation of surface cells yields a mature epidermal architecture with surface keratinization.
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12. EVENTS IN PRIMARY UNION: Second Week
There is continued collagen accumulation and fibroblast proliferation.
The leukocyte infiltrate, edema, and increased vascularity are substantially diminished.
The long process of "blanching" begins, accomplished by increasing collagen deposition within the incisional scar and the regression of vascular channels.
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13. PRIMARY UNION OF SKIN WOUNDS
A, The incised wound as well as suture track on either side are filled with blood clot and there is inflammatory response from the margins.
B, Spurs of epidermal cells migrate along the incised margin on either side as well as around the suture track. Formation of granulation tissue also begins from below.
C, Removal of suture at around 7th day results in scar tissue at the sites of incision and suture track.
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14. Healing by Second intention
Healing of a wound having the following characteristics:
open with a large tissue defect, at times infected;
having extensive loss of cells and tissues;
the wound is not approximated by surgical sutures but is left open.
The basic events in secondary union are similar to primary union
Differ in having a larger tissue defect which has to be bridged.
Hence healing takes place from the base upwards as well as from the margins inwards
Results in a large and sometimes ugly scar
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15. Healing by Second intention
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16. EVENTS IN SECONDARY UNION
Initial haemorrhage.
As a result of injury, the wound space is filled with blood and fibrin clot which dries.
Inflammatory phase
initial acute inflammatory response
followed by appearance of macrophages which clear off the debris as in primary union.
Epithelial changes.
As in primary healing, the epidermal cells from both the margins of wound proliferate and migrate
into the wound in the form of epithelial spurs till they meet in the middle and re-epithelialise the gap completely.
However, the proliferating epithelial cells do not cover the surface fully until granulation tissue from base has started filling the wound space
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17. EVENTS IN SECONDARY UNION
Granulation tissue
Main bulk of secondary healing is by granulations.
Granulation tissue is formed by proliferation of fibroblasts and neovascularisation from the adjoining viable elements.
Its deep red, granular and very fragile.
With time, the scar on maturation becomes pale and white due to increase in collagen and decrease in vascularity.
Specialised structures of the skin like hair follicles and sweat glands are not replaced unless their viable residues remain which may regenerate.
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18. EVENTS IN SECONDARY UNION
Wound contraction.
Its an important feature of secondary healing, not seen in primary healing.
Due to the action of myofibroblasts present in granulation tissue, the wound contracts to one-third to one-fourth of its original size.
Wound contraction occurs at a time when active granulation tissue is being formed.
Presence of infection
Bacterial infection may delays the process of healing due to release of bacterial toxins
These provoke necrosis, suppuration and thrombosis.
Debridement: Surgical removal of dead and necrosed tissue, helps in preventing the bacterial infection of open wounds.
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19. Secondary Union Of Skin Wounds
A, The open wound is filled with blood clot and there is inflammatory response at the junction of viable tissue.
B, Epithelial spurs from the margins of wound meet in the middle to cover the gap and separate the underlying viable tissue from necrotic tissue at the surface forming scab.
C, After contraction of the wound, a scar smaller than the original wound is left.
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20. Differences between Primary and Secondary union of wounds
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22. Complication of Wound Healing
Infection
Implantation : epidermal cyst
Pigmentation: rust-like colour due to staining with haemosiderin.
Deficient scar formation: inadequate formation of granulation tissue
Incisional hernia
Hypertrophied scars and keloid formation: Excessive formation of collagen in healing
Excessive contraction: Dupuytren’s (palmar) contracture, plantar contracture and Peyronie’s disease (contraction of the cavernous tissues of penis).
Neoplasia. Rare, e.g. squamous cell carcinoma in Marjolin’s ulcer i.e. a scar following burns on the skin
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23. Complication of Wound Healing
KELOID
EPIDERMAL CYST
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24. Complication of Wound Healing
Pigmentation of Wound
Dupuytren’s (palmar) contracture
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25. Complication of Wound Healing: Incisional hernia
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Fracture Healing
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Fracture Healing
Fracture results in well defined tissue response to remove the debris and to re-establish vascular supply and to produce a new skeletal matrix.
The timing and histology of process of healing is dependent on location of fracture and local and systemic factors.
Depending on this factors healing take place in either of two ways, i.e.:
Primary Bone healing
Secondary bone healing
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Primary Bone Healing
It take place when in following condition
Excellent anatomic reduction
Minimal or no mobility
Good vascular supply at fracture site
It occurs in two different ways i.e.:
Gap Healing
Contact Healing
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Gap Healing
Even with excellent rigid fixation, a perfect anatomic reduction rarely exist due to deforming forces like muscle pull and function
In such cases blood vessels from periosteum, endosteum and haversian canal invade the gap, bridging mesenchymal osteoblastic precussors.
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Gap Healing
Bone is directly deposited on the fracture fragmenst without resorption and cartilage formation.
Gap = < 0.3 mm – lamellar bone forms directly.
Gap = 0.3 – 1mm woven bone forms first followed by lamellar bone
Healing takes place over 6 weeks.
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Contact healing
When there is adequate contact, essentially a zero gap, then healing take place through contact heatling.
There is Osteoclastic activity at the fracture ends which results in bone resorption and finally remodelling by Bone metabolising unit (BMU), Bone repair unit (BRU), and bone remodelling unit (BRU).
There is formation of osteon which forms the bone again between gap created in remodelled bone.
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32. Secondary Bone healing
It take place in fracture without surgical intervention and after semi-rigid fixation.
It takes place in four stages:
Intermediate reaction
Procallus formation
Osseous callus formation
Remodelling
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A, Haematoma formation and local inflammatory response at the fracture site.
B, Ingrowth of granulation tissue with formation of soft tissue callus.
C, Formation of procallus composed of woven bone and cartilage with its characteristic fusiform appearance and having 3 arbitrary components — external, intermediate and internal callus.
D, Formation of osseous callus composed of lamellar bone following clearance of woven bone and cartilage.
E, Remodelled bone ends; the external callus cleared away. Intermediate callus converted into lamellar bone and internal callus developing bone marrow cavity
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References
Robbinson's basic pathology 8 ed
Harsh Mohan - Textbook of Pathology 6th Ed.
Color atlas of pathology
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