Skin grafts
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Skin grafts






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Skin grafts Skin grafts Presentation Transcript

  • Physiology of Skin Grafts
  • SKIN: Physiology & Function• Epidermis: – protective barrier (against mechanical damage, microbe invasion, & water loss) – high regenerative capacity – Producer of skin appendages (hair, nails, sweat & sebaceous glands)
  • SKIN: Physiology & Function• Dermis: – mechanical strength (collagen & elastin) – Barrier to microbe invasion – Sensation (point, temp, pressure, proprioception) – Thermoregulation (vasomotor activity of blood vessels and sweat gland activity)
  • SKIN: Physiology & Function• Immunological surveillance• Most skin is thin, hair-bearing, has sebaceous glands• Skin of palms/soles/flexor surface of digits is thick, not hair-bearing, no sebaceous glands• Vascular supply confined to dermis
  • SKIN: Anatomy
  • SKIN: Anatomy
  • Skin Grafts: Classification• Full thickness skin grafts: - epidermis & full thickness of dermis• Split skin graft: - epidermis & a variable proportion of dermis - thin, intermediate or thick
  • Skin Grafts: SSG
  • Skin Grafts: Classification Autografts Isografts Allografts Xenografts
  • Skin Grafts: “Process of Take”• Vascularity of donor site• Tolerance to ischaemia• Metabolic activity of the graft
  • Skin Grafts: “Process of Take”• 4 Phases: – Fibrin adhesion – Plasmatic imbibition – Revascularization: Inosculation & capillary ingrowth – Remodelling: Revascularization & fibrous attachment in restoring normal histological architecture
  • Skin Grafts: “Process of Take”• Plasmatic Imbibition: – Initially graft ischaemic (24 – 48 hrs) – Fibrin adhesion – Imbibition allows the graft to survive this period – ? Important for nutrition of graft – ? Stops drying out
  • Skin Grafts: “Process of Take”• Inosculation & capillary ingrowth: – At 48 hrs – Through fibrin layer – Capillary buds from recipient bed contact graft vessels – Open channels (neo-vascularization)  pink graft
  • Skin Grafts: “Process of Take”• Revascularization & fibrous attachment: – Connection of graft & host vessels via anastomoses (inosculation) – Formation of new vascular channels by invasion of graft (neovascularisation) – Combination of old & new vessels (revascularisation) – Fibroblast proliferation: conversion of fibrin adhesion  fibrous tissue attachment (anchorage within 4 days)
  • Skin Grafts: “Process of Take”
  • Skin Graft Take: EpidermisDays Histological changes0–4 Epithelium doubles; crusting, scaling of epidermis; swelling of nuclei & cytoplasm; epithelial cell migration to surface; mitosis of follicular & granular cells3 ++ mitotic activity in SSG not FTSG4–8 Proliferation & thickening of epithelium (up to 7x) desquamationWeek 4 Epidermis returned to normal thickness
  • Skin Graft Take: EpidermisDay Histochemical changes4 Increased RNA in basal cells, indicating protein synthesis10 RNA returns to normal
  • Skin Graft Take: Dermis• Fibrous component:Collagen Hyalinized early and progressively replaced with new fibres by 6 weeks; Turned over 3-4X faster than normal skin.Elastin Accounts for resilience; Days 3-7 fragment; Replaced 4-6 weeks.Extracellular Proteins direct the behaviour ofmatrix keratinocytes; Communication between keratinocytes & fibroblasts.
  • Skin Graft Take: Dermis• Appendages: - sweating dependent on no. of transplanted sweat glands & degree of sympathetic reinnervation; will sweat like recipient site in FTSG only - sebaceous gland activity mostly in thicker grafts: SSG usually dry & shiny - hair grows from FTSG if well taken with no complications
  • Skin Graft Healing• Initially white then pinkens with new blood supply• Lymphatic drainage by day 6• Collagen replacement from day 7 to week 6• Vascular remodelling for months
  • Skin Graft Healing• Contraction: - shrinks immediately due to elastic recoil: – FTSG 40%; medium SSG 20%; thin SSG 10%. - secondary contracture as heals: - FTSG remains same size after above shrinkage; - SSG will contract as much as possible; - more dermis = less contraction - ? Due to myofibroblasts
  • Skin Graft Healing• Reinnervation: – from margins to bed; – 4/52 to 2 years; – Depends on graft thickness and bed; – Uneventful healing leads to near normal 2PD; – Cold sensitivity can be a problem.
  • Skin Graft Expansion• Based on principle that wounds reepithelialized from the periphery• Expansion provides larger areas from which epithelium can grow• Larger areas can be covered with less skin
  • Skin Graft Expansion• Meshing - covers large area - easier to contour - fluid can drain through holes - cosmetic results less than ideal - various mesh ratio
  • Skin Graft Survival• Meticulous technique• Atraumatic graft handling• Well vascularized bed• Haemostasis• Immobilization• No proximal constricting bandages
  • Skin Graft Failure• Haematoma• Infection• Seroma• Mobility• Inappropriate bed• Dependency• Arterial insufficiency• Venous congestion• Lymphatic stasis• Technical – upside-down