Wound, Wound Healing and Closure Part 2

Phases of Wound Healing

Hemostasis → Inflammatory → Proliferative → Maturation/Remodeling

Hemostasis Phase

Reflex vasoconstriction, primary hemostasis, secondary hemostasis

Inflammatory Phase

Days 1–5; neutrophils arrive first to destroy bacteria and clear debris; macrophages replace neutrophils and release growth factors

Inflammatory Phase Signs

Localized edema, pain, fever, erythema peaking within 24 hours, subsiding by day 3

Neutrophils Role

First cells to arrive in inflammatory phase; destroy bacteria and clear debris

Macrophages Role

Replace neutrophils; essential for healing; release VEGF, PDGF, EGF, FGF; promote fibroblast activity and matrix formation

Pus Composition

Dead neutrophils + tissue debris

Proliferative Phase

Days 5–14; angiogenesis, fibroplasia, epithelialization, wound contraction

Angiogenesis

Driven by VEGF, FGF, TGF‑β, angiogenin, angiopoietin

Fibroplasia

Fibroblasts migrate and produce collagen (beginning of tensile strength); Collagen III → Collagen I

Peak Collagen Production

Day 7–14

Epithelialization

Mobilization and migration of epithelial cells from wound edges; needs granulation tissue in full‑thickness wounds

Wound Contraction

Mediated by myofibroblasts; reduces wound size; may cause contractures if excessive

Maturation/Remodeling Phase

Day 14 until done; lasts months to years; ECM transitions into mature collagen matrix

Tissue Strength at 3 Weeks

~20% regained

Maximum Tissue Strength

~70–80% of original strength (only urinary bladder and bone regain full strength)

Factors Affecting Wound Healing

Infection, seromas/hematomas, trauma, anemia/blood loss, age/weight, nutrition

Infection and Healing

Causes mechanical separation; releases hyaluronidase, collagenase, fibrinolysis, coagulase, hemolysis

Infection Prevention

Thorough debridement, hemostasis, decrease dead space, decrease operation time

Seromas/Hematomas Effect

Decrease healing by mechanical separation and providing medium for bacterial infection

Trauma Effect on Healing

Prolongs early phase of healing; decreases gain in tensile strength

Anemia/Blood Loss Effect

Local tissue hypoxia inhibits wound healing responses; inhibits fibroblastic function decreasing collagen development

Age Effect on Healing

Geriatric: decreased fibroplasia and cell proliferation; Young: faster but tissues more friable, don't hold sutures well

Vitamin A Effect

Increases wound healing

Vitamin K Effect

Necessary for clot formation

Vitamin C Effect

Needed for hydroxylation of proline and lysine for collagen synthesis

Tensile Strength Improvement

Continues for up to one year during maturation phase

Scar Formation

Grows paler as new vessel construction tapers off

Wound Contraction Duration

Occurs over weeks or months