Types of wound closure

Primary Intention - The Clean Cut

• Healing of a clean, uninfected surgical wound where edges are precisely apposed.
• Characterized by minimal tissue loss and a fine, linear scar.

⭐ Wound tensile strength is only ~10% of normal skin at 1 week, increasing to ~70-80% by 3 months, but never regaining 100% strength.

Secondary Intention - Healing Naturally

• Mechanism: Wound is left open to heal from the base up. Relies on the body's natural healing capacity.
• Process: Involves significant granulation tissue formation, followed by wound contraction and epithelialization.
• Indications:
  • Contaminated or infected wounds (e.g., abscess cavities).
  • Wounds with significant tissue loss (e.g., deep ulcers, burns).
  • When approximation of edges is not feasible.
• Outcome: Slower healing, more inflammation and a larger, more prominent scar compared to primary intention.

⭐ High-Yield Fact: Wound contraction, a key feature of secondary healing, is primarily mediated by myofibroblasts.

Tertiary Intention - The Waiting Game

Also known as delayed primary closure (DPC). The wound is intentionally left open-typically for 4-7 days-to allow for initial drainage, debridement, and granulation, before being formally closed.

• Goal: Reduce bacterial load in heavily contaminated wounds.
• Indications:
  • Grossly contaminated wounds (e.g., trauma, foreign bodies).
  • Animal or human bites.
  • Abscess cavities after incision and drainage.

⭐ Tertiary intention combines the initial phase of healing by secondary intention with a final closure by primary intention, resulting in less scarring than secondary intention alone.

Grafts & Flaps - The Reinforcements

• Grafts: Tissue transferred without its own blood supply, relying on the recipient bed for neovascularization.

  • Split-Thickness (STSG): Epidermis & partial dermis. Good for large areas; prone to contraction.
  • Full-Thickness (FTSG): Epidermis & entire dermis. Better cosmesis, less contraction; requires a well-vascularized bed.

• Flaps: Tissue transferred with its intact blood supply. Essential for covering avascular structures (bone, tendon).

  • Random Pattern: Blood supply from the subdermal plexus. Length-to-width ratio is critical (e.g., < 3:1).
  • Axial Pattern: Incorporates a named direct cutaneous artery.
  • Free Flap: Tissue and its vessels are detached and reanastomosed to vessels at the recipient site.

⭐ The most common cause of flap failure is venous thrombosis, leading to congestion and subsequent arterial compromise.

High-Yield Points - ⚡ Biggest Takeaways

• Primary intention involves immediate suture of clean, approximated wound edges, resulting in minimal scarring.
• Secondary intention is for contaminated or large tissue-loss wounds; they are left open to heal via granulation tissue formation.
• Tertiary intention (Delayed Primary Closure) involves cleaning a contaminated wound, waiting 4-7 days for signs of healing, then suturing it closed.
• The key determinant for closure type is the degree of contamination and tissue loss.
• Secondary intention healing is the slowest and results in the most significant scarring.