What are the phases of graft healing?

Phases of Skin Graft Healing

Skin graft healing occurs through three sequential and overlapping phases: (1) plasmatic imbibition, (2) revascularization (including inoculation and neovascularization), and (3) remodeling, with complete healing typically achieved within 2 weeks for most grafts. 1, 2

Phase 1: Plasmatic Imbibition (Days 0-2)

• Plasmatic imbibition is the initial survival mechanism where the graft absorbs plasma and nutrients directly from the wound bed through diffusion before any vascular connections are established 1
• This phase begins immediately after fibrinous adherence, where fibrin creates the initial attachment between graft and wound bed 1
• The graft remains avascular during this period but survives through passive absorption of plasma fluid 1

Phase 2: Revascularization (Days 2-5)

This phase involves two critical overlapping processes:

Inoculation (Days 2-3)

• Blood vessels from the wound bed begin to connect with existing graft vessels through a process called inoculation 1
• Capillary widening in the wound bed appears by day 1 and increases until day 4 2

Neovascularization/Angiogenesis (Days 2-5)

• New capillary buds and sprouts originate from the wound bed and grow toward the graft, first appearing at day 2 2
• Blood filling of the graft's own capillaries occurs by day 3 2
• Almost complete restoration of the original skin microcirculation is achieved by day 5 through interconnections between wound bed microvasculature and graft vessels 2
• The angiogenic response is temporary and primarily directed from the wound bed upward into the graft 2

Phase 3: Remodeling (Days 5 onwards)

• The remodeling phase begins around day 5 and involves synthesis and reorganization of new protein and structural components 3
• Collagen deposition and maturation occur during this phase, with collagen I detected by day 5 and collagen IV (indicating endothelial cell presence) by day 10-14 3
• Most skin-grafted wounds achieve complete epithelialization (100% wound closure) within 2 weeks, with 46% of grafts completely healed by postoperative day 7 4

Important Clinical Considerations:

• Split-thickness grafts "take" better than full-thickness grafts due to their enhanced ability to undergo these healing phases, though they may be less cosmetically attractive 1
• The wound bed must be healthy granulation tissue or sufficiently vascular tissue to support these healing phases 1
• Factors that can delay healing beyond 2 weeks include seroma formation, hypergranulation tissue, and malnutrition (low prealbumin levels) 4