A 32-year-old woman undergoes elective cesarean section for breech presentation. On postoperative day 5, the surgical wound shows erythema, warmth, and purulent discharge. Culture grows Staphylococcus aureus. Histopathology of the wound edge reveals predominantly neutrophilic infiltrate with fibrin deposition and minimal collagen deposition. Which phase of wound healing is MOST likely impaired in this patient?

## Phase of Wound Healing Impaired **Key Point:** The clinical presentation of active infection (erythema, warmth, purulent discharge) on postoperative day 5 with predominant neutrophilic infiltrate indicates the wound is still in the inflammatory phase, but progression to the proliferative phase is blocked. ### Timeline of Normal Wound Healing Phases | Phase | Timeline | Key Cellular Events | Histologic Features | |-------|----------|-------------------|---------------------| | Hemostatic | 0–minutes | Platelet aggregation, fibrin clot formation | Platelet plug, fibrin mesh | | Inflammatory | 0–3 days (extends to ~1 week) | Neutrophil infiltration, macrophage recruitment, cytokine release | Neutrophils, fibrin, minimal collagen | | Proliferative | 3–21 days | Fibroblast migration, collagen synthesis, angiogenesis, epithelialization | Granulation tissue, collagen deposition, new vessels | | Remodeling | 3 weeks–2 years | Collagen cross-linking, matrix reorganization, scar maturation | Organized collagen, reduced cellularity | **High-Yield:** In this case, the histology shows **minimal collagen deposition** despite being on postoperative day 5. Normally, by day 5, the proliferative phase should be well underway with active collagen deposition by fibroblasts. The bacterial infection (S. aureus) has prolonged the inflammatory phase and prevented transition to the proliferative phase. **Clinical Pearl:** Wound infection delays healing by: - Prolonging neutrophil-mediated inflammation - Releasing proteases that degrade newly formed collagen - Preventing fibroblast recruitment and activation - Inhibiting angiogenesis **Mnemonic:** **FIBROBLAST** — Fibroblasts are the hallmark of the Proliferative phase; their absence or dysfunction indicates impaired proliferative phase. ### Why Proliferative Phase Is Impaired The histopathology explicitly states **minimal collagen deposition**, which is the cardinal feature of the proliferative phase. Collagen synthesis by fibroblasts begins around day 3 and peaks during days 5–7 in uncomplicated wounds. The presence of active infection prevents this transition. [cite:Robbins 10e Ch 3]