Wound Healing
• A wound is a breach in the continuity of normal tissues
• Wound healing
– Repair or reconstitution of a defect in an organ or tissue
especially skin
– Represents the response of an organism to a physical disruption
of tissue /organ to re establish homeostasis of that tissue and to
stabilize the entire organisim’s physiology.
– Two processes by which this re-establishment of homeostasis
occurs:
• Scar formation-substitution of different cellular matrix
• Regeneration-recapitulation of developmental process to recreate
architecture of original organ.
Semantics of wound healing
• Primary intention healing
– Healing of surgical wounds reapproximated
by sutures and in the absence of
complications
• Secondary intention healing
– Wounds not approximated and subsequently,
the defect is filled with granulation tissue
classification
• Acute wound
– Wound that has occurred within 3 to 4 weeks
• Closed wounds like bruises and contusions
• Open wounds like abrasions and lacerations
• Complex wounds like crush wounds and avulsions
• Injuries to special tissues like nerves, bones and vessels
• Chronic wound
– Wound persisting beyond 4 to 6 weeks
• Ulcers
• Pressure sores
Phases of wound healing
• Hemostasis and inflammation
– Day 0 to day 6
• Proliferation
– Day 6 to day 14
• Remodelling
• Day 8 through 1 year
Phases of wound healing
• Inflammatory phase
– Begins immediately following tissue injury
– Attainment of hemostasis,removal of dead tissue and prevention of
infection
– Disrupted vessels allow blood elements into the wound and platelet
aggregation plugs the disrupted vessel
– Attraction of inflammatory cells initally neutrophills and later on by
monocytes
– The neutrophils remove dead tissue by phagocytosis and prevent
infection .
– Monocytes /macrophages follow neutrophills and appear 48 to 72 hours
after injury. These phagocytose debris and bacteria and produce
growth factors necessary for production of extra cellular matrix
– Lymphocytes are the last cells to enter the wound. Its role is not well
known although they may be important in next phase of wound healing
• Proliferative phase
– It occurs between 4 to 21 days following injury
– Epithelialization is initiated by macrophages
upon stimulating fibroblasts.
– Fibroblasts cause keratinocytes to proliferate
– Keratinocytes adjacent to wound change their
phenotype
– Regression of desmosomal connections frees
the cells and allow them to migrate
– Collagen replaces the proteoglycans
– Fibrin matrix is replaced by granulation tissue
– Granulation tissue is composed of fibroblasts,
macrophages and endothelial cells.
• Remodelling phase
– Longest part of wound healing and lasts from 21`
days to 1 year.
– It starts once wound is filled with granulation tissue
and re epithelialization is complete.
– Characterized by process of wound contraction and
collagen remodelling
– Wound contraction is produced by myofibroblasts
which are special type of fibroblasts with intracellular
actin microfilaments in it
– Replacement of type III collagen by type I
– At 3 weeks of remodelling phase wound strength is
about 20%.
Abnormal wound healing
• Inadequate regeneration
– It occurs in nerves where regeneration is
compensated for by replacement with scar tissue
• Excessive regeneration
– It occurs after nerve injuries forming neuromas and in
skin giving rise to hyperkeratosis
• Inadequate scar formation
– In diabetes and vitamin c deficiency
• Excessive scar formation
– Hypertrophic scarring and keloids
Wound care
• Fundamentals
– Evaluation by a physician
– Tetanus prophylaxis
– Etiology of wound and presence of any
comorbid condition influencing wound healing
– Laboratory investigations like serum albumin
levels,ESR,blood glucose levels and complete
blood count.
– Documentation and photograph of the wound
to monitor progression
Basics of wound care
Causes of problems in wound
healing
• Three main causes are
– Age
– Ischemia
– Bacterial infection
Age and wound healing
• Decline in wound healing rate in elderly
• It is due to accelerated ageing of
fibroblasts, decreased production of
growth factors, decreased ability to survive
hypoxic and toxic stresses and decreased
production of collagen.
Ischemia and wound healing
• Adequate oxygenation is important to prevent
complications
• Improvement of oxygenation to wound by
– Elevation
– Offloading
– Debridement
– Pain control
– Warmth
– Cessation of smoking
– hydration
Infection and wound healing
• Quantitative culture of 105 bacteria /gram
of tissue is diagnostic of infection
• Bacteria set up an environment of free
radicals,and secreted toxins and
proteases. They degrade growth factors
• They increase the metabolic demands on
the healing wound
Adjuncts to wound healing
• Debridement
– Decreases the bioburden
– It can be
• surgical done by surgeons in operating rooms
• ,enzymatic,
• Mechanical by pressurized water
• autolytic by leukocytes
• Biological by maggot therapy
Negative pressure wound therapy
• Tremendous advance in wound care
• It decreases the edema,removes the
deleterious enzymes from the wound,and
decreases the bacterial count
• Stimulates the vascular proliferation
Hyperbaric oxygen
• It is 100% oxygen saturated at 2 to 3
atmospheres raises dissolved oxygen
saturation in tissues
• It increase the oxygen at microcirculation
and better control of infection and wound
proliferation
Growth factors
• Platelet derived growth factor
– Increases the healing in chronic wounds
• Vascular endothelial growth factor
enzymes
• Enzymatic debridement like papain and
urea
• Collagenase
• Non invasive and painless
• Less effective than surgical debridement
Dressings
• Films
• Gauzes
• Hydrogels
• Hydrocolloids
• Alginates
• foams
Skin substitutes
• Cultured keratinocytes
• Dermal constructs
• Alloderms
Useful in burn wounds