Wound Healing😊

Wound Healing

Phases

  • Hemostasis → Inflammation → Proliferative → Remodeling

Wound Strength

  • 10% of normal after 1 week
  • Maximum (70-80% of normal) after 3 months/12 weeks
  • Original strength is never regained

Collagen Type

  • Initially Type 3
  • Remodels to Type 1
  • Ratio of Type 1 : Type 3 = is 4 : 1 in remodeling

Types of Healing: Intentions

  • Primary intention:
    • Clean incised wound
    • Sutured
    • Yields good scar
  • Secondary intention:
    • Wound left open
    • Gradual contracture
    • ↑ granulation tissue
    • Hypertrophic scar
  • Tertiary intention:
    • (Delayed primary closure):
      • Wound left open initially
      • Sutured after a few days
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Events of Wound Healing by Day

  • Day 0-2
      • Stage
      Timing
      Cells
      Notes
      Blood Clot
      First 2 days
      Platelets, Fibrin
      Platelets are the first cells
      Acute Inflammation
      Early response
      Neutrophils
      ã…¤
      Thin Epithelial Layer
      Begins Day 2
      Epithelial cells
      New epithelial covering starts
  • Day 3-21
      • Phase
      Key Events
      Timeline
      Chronic Inflammation
      Macrophages dominate
      ã…¤
      Granulation Tissue
      Hallmark of repair, very red (proliferating blood vessels)
      Starts Day 3,
      Max on Day 5
      Collagen Formation
      Collagen deposition begins
      Starts Day 3,
      Max on Day 21 (Week 3)

Factors and Characteristics of Wound Healing

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  • Needed Vitamins/Minerals: Vitamin C, Zinc.
  • Most Common Cause of Delayed Wound Healing:
    • Infection
    • DM, Steroids
  • Wound Strength: Never 100% of normal strength.
  • Wound Contraction: By myofibroblasts.
  • Collagen Type Changes:
    • Starts as collagen Type III.
    • Changes to collagen Type I (strongest) by end.
    • Ratio at End (Type III : Type I): 1:4. (Strongest collagen, Type I, is more).

Excessive Wound Healing

KELOID
KELOID
Hypertrophic scar
Hypertrophic scar

Proud Flesh:

  1. Excessive granulation tissue (red).
  1. Proper scar doesn't form.

Stain for Differentiating Keloid/Hypertrophic Scar (and muscle/collagen):

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  • Masson Trichrome Stain.
    • Red: Muscle.
    • Blue: Collagen.
Feature
Keloid
Hypertrophic Scar
M/c site
Sternum, shoulder region
Extensor surface
Predisposition
Racial (dark-skinned people)
More common in children
Growth
More aggressive,
Grows beyond scar boundary
Remains within scar boundaries
Progression
Does not subside
Subsides with time & pressure
Mx
Intralesional triamcinolone
Silicone pads/gel
Microscopically
Haphazard collagen bundles 
Thin, orderly collagen fibers 

To prevent recurrence:

  • Intralesional steroids +
  • Intramarginal excision +
  • f/b Radiation therapy