Dr. Mundy and Dr. Tillis talk the basics of wound healing and skin grafts. Tune in to hear! Great for medical students or any learners excited about Plastic Surgery.

Full Notes

Wound healing methods

• Primary closure: bring wound edges together and adhere them
  • When to do this? Clean, fresh wounds, happens within hours
• Secondary intention: leaving something to heal from the inside out through contraction and epithelialization of the wound
  • When to do this? Smaller wounds with no critical structures exposed
• Delayed primary closure: leave a wound to start in secondary intention followed by a primary closure, converting a subacute wound into an acute wound (ex: sharp debridement) and then closing it primarily
• Intention vs. closure – no real difference between the terms often used interchangeably
• Chronic wound – a wound that hasn’t healed in 3 months
• Reconstructive Ladder & reconstructive elevator
  • A list of options for wound closure going from least invasive to most
  • The elevator implies that you may not always necessarily go through each step to get to a more invasive intervention

Skin Layers

• Epidermis
  • Stratum corneum, stratum lucidum , stratum granulosum, spinosum, basalis ; superficial to most deep
  • Primary cell = keratinocytes
  • Stratum basalis = has active keratinocytes- less viable as you get more superficial
• Dermis
  • 2 Layers – papillary superficial to the reticular dermis
  • Has hair follicles, sebaceous glands, sweat glands, and nerve fibers
• Subdermal plexus : vascular junction between the deep reticular portion of the dermis and the underlying subcutaneous fat
• Function :
  • Largest organ
  • 16% of body weight
  • Offers protection from UV light
  • Mechanical, chemical, and thermal protection
  • Carries out vitamin D synthesis

Wound Healing

• Coagulation precedes the 3 major steps
  • first couple minutes to hours
  • driven by platelets, fibrin, growth factors
• (1) Inflammatory stage : first couple day
  • Neutrophils and macrophages
    • Neutrophils are important in the first 48 hours and for inflammation and phagocytosis
    • Macrophages at 48 – 96hrs orchestrates the growth factors (very important)
  • Vasoconstriction  vasodilation (increase permeability)
    • Chemotaxis, cell  migration, and cellular responses
  • (2) Fibroproliferative stage; day 4 – 1month
    • Driven by macrophages and fibroblasts
    • Fibrobalsts at day 7 lead to production of collagen leading to increased tensile strength
      • Angiogenesis and epithelialization also occur
    • (3) Maturation and remodeling :
      • 1 month – 1 year
      • Driven by myofibroblasts for wound contraction and epithelial cells
      • Goals:
        • achieve an equilibrium between collagen breakdown and synthesis
        • Get more organized and stronger collagen ; type I replacing type III & IV collagen
      • Decreased water content and decreased cell count by the end of this stage

Skin healing

• Re-Epithelialization :
  • Loss of contact inhibition, cells mobilize from edges towards the center until they meet other cells, cells in the basal layer multiply and new cells differentiate into the layers of the epidermis
• Contraction:
  • Due to myofibroblasts; Peaks Day 10-21
  • Primary vs. Secondary Contraction
    • Primary = how much the graft contracts initially
    • Secondary = contraction over time as it heals
    • Determined by amount of elastin in the dermis (more elastin = more primary contraction)

Skin grafts

• Full Thickness Skin Graft (FTSG)
  • Epidermis + all dermis
  • Use when you want more skin tone match, often in the face
  • Has higher primary contraction and less secondary
• Partial or Split Thickness Skin Graft (STSG)
  • Epidermis + part of dermis
  • Use for larger areas
  • Has lower primary contraction and higher secondary contraction given lower elastin content
• Things to consider when choosing full vs. split
  • Available donor site
    • If you require a large area  split thickness skin graft
      • Possible areas : belly, groin crease
    • Location of graft site
      • If face, may opt for full thickness for skin tone match
    • Contraction –> full thickness will contract less
  • Meshing
    • SPTSG can be run through a device that pokes holes in the graft allowing it to expand to an area 3-4x the size of the original graft
    • Function
      • 1) increases size of the graft
      • 2) decreases the chance of hematoma or seroma formation as it can allow fluid to escape
    • How Skin Grafts Heal (must-know for students!)
      • Imbibition
        • Up to 48 hours
        • Graft absorbs nutrients
      • Inosculation
        • Day 3-5
        • Connection of recipient and donor vessels in the bed
      • Neovascularization
        • After day 5
        • New blood vessel growth
      • Why Do Skin Grafts Fail?
        • Interruption of healing
          • Hematoma
          • Shearing forces
            • Prevent by putting a bolster
          • Infection – bacteria > 10^5
          • Poorly perfused wound bed

 

Keloids vs Hypertrophic Scars

• Main difference = keloids extend beyond the borders of the original scar
• Collagen
  • Ratios of type I to type III collagen – scars always have more type III collagen than normal skin
    • Normal Skin 4:1
    • Keloids – 3:1
    • Hypertrophic – 2:1
  • Orientation
    • Hypertrophic scar – parallel orientation
    • Keloids – disoriented orientation

Scar removal

• Hypertrophic scar treatment = Excising only will commonly not lead to recurrence
  • Common areas = areas of tension, flexor surfaces
• Keloid treatment = multimodal therapy including excision + (steroids, 5FU, cryotherapy, or radiation)

 

How to Minimize Scars

• Minimize tension on the closure
• Minimize inflammation
  • Permanent suture  train tracks
• No infection
• Post-op optimization
  • Scar massage (start 3 weeks after surgery when incision is healed)
  • Sun protection (for first year)
  • Silicone based tapes can help by keeping area moist