Wound Healing

Types of Wound Healing: 

  • Primary:

    • Direct approximation of wound edges w\in hours of wound creation
    • Example: sutures, stables, skin grafts
    • Contraindications: bites, infections, crush injuries, > 6-8 hrs since injury, retained foreign body
  • Secondary:

    • Wound left open to heal spontaneously: epithelialization, contraction, granulation
    • Requires dressing changes
    • Inferior cosmetic result
  • Delayed primary:

    • When the wound is left open (debridement, packing, antibiotics) to control infection and form granulation tissue for a few days, then the wound can be closed (suturing, graft, flap)

 

Classification of Wound Healing: 

  Definition Example Risk of infection
Clean Operative, non-traumatic, no inflammation, no break in technique, no entering of resp\GI\GU Thyroidectomy, hip replacement <2%
Clean-contaminated Operative, non-traumatic, entering resp\GI\GU w\out significant spillage Tonsillectomy, cholecystectomy 5-10%
Contaminated Operative w\ major break in technique, traumatic, entering resp\GI\GU w\ gross spillage, evidence of inflammation Large bowel resection, biliary or GU surgeries w\ infected bile or urine 15%
Dirty Operative, traumatic, fecal contamination, foreign body, necrosis, pus, perforation Empyema, abscess I&D, wound debridement 40%

 

Stages of Wound Healing: 

  • Inflammatory (1-6 days): limits damage and prevents further injury:

    • Hemostasis: vasoconstriction + platelet plug (within minutes)
    • Vasodilation and increased permeability:
    • Cell migration: margination, diapedesis, chemotaxis
  • Proliferative (day 4 – week 3):

    • Matrix formation:
      • Fibroblast migration (7 day)
      • Collagen synthesis (D5-wk3); mainly type III here -> tensile strength begins to inc at D4-5
      • Glycosaminoglycan production
    • Angiogenesis: VEGF\NO
    • Epithelialization: begins 24-48 h
  • Remodeling (week 3 – 1 year):

    • Collagen: increased collagen synthesis and organization (type I replaces type III, until normal 4:1 ratio is achieved)
    • Contraction: due to myofibroblasts
    • Scar formation and remodeling: begins at D21

 

Factors Affecting Wound Healing:

Local

Systemic

–   Blood\oxygen supply (atherosclerosis, Raynaud’s, scleroderma, PVD)

–   Retained foreign body

–   Infection (inc risk due to hematoma\seroma)

–   Temperature

–   Radiation

–   Age

–   Hereditary conditions: collagen vascular diseases (EDS, progeria, Werner syndrome)

–   Nutritional (proteins, vit C)

–   Smoking

–   Chronic ds (DM, Ca, CVD)

–   Immunodeficiency (steroids, chemo, radio)

 

Abnormal Wound Healing:

Hypertrophic scar

Keloid

–   Elevated, but remains w\in borders of original scar

–   Type III collagen oriented parallel to epidermal surface + abundant myofibroblasts and collagen

–   Associated w\ poor technique during suturing

–   Site: flexor surfaces

–   More common than keloids, less likely to recur after therapy

–   Scar growing outside original wound borders

–   Disorganized type I & III collagen, hypocellular collagen bundles

–   Related to genetic and endocrine influences (inc in preg and puberty)

–   Site: sternum, shoulder, face, earlobes

–   More resistant to therapy

 

Random notes:

Wound healing 1

 

 


Download the PDF version: here


References:

  • Salah Aldekhayel’s lecture
  • Essentials of plastic surgery
  • Toronto notes

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