A 42-year-old man undergoes elective abdominal surgery. His wound heals uneventfully over 3 weeks. Which feature best distinguishes primary intention healing from secondary intention healing in this patient?

## Primary vs. Secondary Intention Healing | Feature | Primary Intention | Secondary Intention | |---------|-------------------|---------------------| | **Wound edges** | Closely approximated (sutured) | Wide gap; edges not opposed | | **Epithelialization** | Rapid; across narrow gap (days) | Slow; from wound margins (weeks–months) | | **Granulation tissue** | Minimal or absent | Abundant and prominent | | **Wound contraction** | Minimal (<10%) | Marked (up to 80%) | | **Scar formation** | Fine, linear scar | Thick, irregular scar | | **Timeline** | 3–4 weeks for strength gain | 4–6+ weeks for epithelialization | | **Examples** | Surgical wounds, clean lacerations | Pressure ulcers, burns, infected wounds | ### Primary Intention (First Intention) Healing 1. **Minimal inflammatory phase** — edges are clean and approximated 2. **Rapid epithelialization** — epithelial cells migrate across a narrow gap (< 1 mm) 3. **Minimal granulation tissue** — collagen deposition occurs in the dermis without prominent granulation tissue 4. **Fine scar** — organized collagen alignment results in a linear scar 5. **Rapid strength gain** — reaches ~70% strength by 3 months ### Secondary Intention (Healing by Granulation) Healing 1. **Prolonged inflammatory phase** — large tissue defect requires extensive cleanup 2. **Abundant granulation tissue** — prominent vascular and fibroblastic response 3. **Wound contraction** — myofibroblasts contract the wound, reducing defect size by 60–80% 4. **Epithelialization from margins** — epithelial cells migrate from wound edges inward 5. **Thick, irregular scar** — disorganized collagen and myofibroblast remnants **Key Point:** The **single best discriminator** is the presence or absence of granulation tissue and the mechanism of epithelialization. Primary intention shows **minimal granulation tissue and epithelialization across a narrow gap**; secondary intention shows **abundant granulation tissue and epithelialization from wound margins**. **High-Yield:** In primary intention, the wound is **closed** (sutured), so epithelial cells bridge a narrow gap directly. In secondary intention, the wound is **open**, so epithelial cells must migrate centripetally from the wound edges—a much slower process requiring prominent granulation tissue. **Mnemonic:** **PIGS** for Primary Intention: - **P**rimary = edges **P**roximated (sutured) - **I**ncision = clean **I**ncision (surgical) - **G**ranulation = **G**ranulation **G**ranulation tissue minimal - **S**car = fine, linear **S**car Contrast with **SCAR** for Secondary Intention: - **S**econdary = **S**econdary intention - **C**ontraction = marked **C**ontraction - **A**bundant = **A**bundant granulation tissue - **R**agged = **R**agged, irregular scar **Clinical Pearl:** Clinically, a surgical wound that is closed with sutures and heals without infection will follow primary intention. A pressure ulcer or burn wound that is left open will heal by secondary intention, taking weeks to months and leaving a prominent scar with potential contracture complications.