Wound Healing Phases: Identifying the Incorrect Statement
Statement D is incorrect—the increase in collagen type 1 does not begin by day 6; rather, collagen type I synthesis begins much earlier, with significant increases detected by day 2 and reaching peak levels by day 7 postoperatively. 1
Analysis of Each Statement
Statement A: Phases include hemostasis and inflammation, proliferation and maturation
- This is CORRECT. The wound healing process consists of four overlapping phases: hemostasis, inflammatory, granulation (proliferation), and maturation 2
- These phases are well-established in the literature and represent the standard framework for understanding wound healing 2
Statement B: Macrophage increase occurs within first 24-48 hours
- This is CORRECT. Following blood clot formation, degranulating platelets release PDGF that stimulates chemotaxis of neutrophils, monocytes, and macrophages, which play key roles in initiating the inflammatory response during the early hemostasis and inflammation phase 2
- Macrophages are recruited early and become the main actors of subsequent wound healing phases, contributing to wound debridement and secreting multiple growth factors 2
Statement C: Fibroblast increase occurs within 4-8 days
- This is CORRECT. During the proliferation phase, PDGF, FGF-2, and TGF-β stimulate the proliferation of fibroblasts that play key roles in extracellular matrix synthesis 2
- The timing of 4-8 days aligns with the granulation/proliferation phase when fibroblast activity peaks 3
Statement D: Collagen type 1 increase starts by day 6 onwards
- This is INCORRECT. Research demonstrates that type I collagen synthesis begins much earlier than day 6 1
- The carboxyterminal propeptide of type I procollagen (PICP) shows a mean concentration increase from 207 μg/L on day 1 to 908 μg/L on day 2 (p < 0.001), representing a statistically significant early rise 1
- By day 7, PICP concentrations reach 79,330 μg/L—representing a 380-fold increase compared to day 1, indicating that collagen type I synthesis is already well-established and peaking by this time 1
- The statement incorrectly suggests collagen type I synthesis "starts" around day 6, when in reality it begins within the first 24-48 hours and is already at very high levels by day 6-7 1
Clinical Significance
Understanding the accurate timeline of collagen synthesis is critical because:
- Early collagen deposition determines wound strength. The strength of wounds is determined primarily by collagen content early in the healing course 3
- Interventions must be timed appropriately. Factors that impair early collagen synthesis (such as corticosteroids, which inhibit inflammatory cell infiltration and collagen synthesis) can significantly compromise wound healing if administered during the critical early phase 2
- Collagen type I specifically contributes to tensile strength. The transition from type III to type I collagen during maturation is what ultimately provides increased wound-breaking strength, but this process begins much earlier than day 6 4, 5