skin graftsw

28

Upload: drmoradisyd

Post on 02-Jun-2015

526 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Skin graftsw
Page 2: Skin graftsw

Physiology of Skin Grafts

Page 3: Skin graftsw

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)

Page 4: Skin graftsw

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)

Page 5: Skin graftsw

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

Page 6: Skin graftsw

SKIN: Anatomy

Page 7: Skin graftsw

SKIN: Anatomy

Page 8: Skin graftsw

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

Page 9: Skin graftsw

Skin Grafts: SSG

Page 10: Skin graftsw
Page 11: Skin graftsw

Skin Grafts: Skin Grafts: ClassificationClassification

AutograftsIsograftsAllograftsXenografts

Page 12: Skin graftsw

Skin Grafts: “Process of Take”

• Vascularity of donor site• Tolerance to ischaemia• Metabolic activity of the graft

Page 13: Skin graftsw

Skin Grafts: “Process of Take”

• 4 Phases:– Fibrin adhesion– Plasmatic imbibition– Revascularization: Inosculation & capillary

ingrowth– Remodelling: Revascularization & fibrous

attachment in restoring normal histological architecture

Page 14: Skin graftsw

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

Page 15: Skin graftsw

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

Page 16: Skin graftsw

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)

Page 17: Skin graftsw

Skin Grafts: “Process of Take”

Page 18: Skin graftsw

Skin Graft Take: Epidermis

Days Histological changes

0 – 4 Epithelium doubles; crusting, scaling of epidermis; swelling of nuclei & cytoplasm; epithelial cell migration to surface; mitosis of follicular & granular cells

3 ++ mitotic activity in SSG not FTSG

4 – 8 Proliferation & thickening of epithelium (up to 7x) desquamation

Week 4 Epidermis returned to normal thickness

Page 19: Skin graftsw

Skin Graft Take: Epidermis

Day Histochemical changes

4 Increased RNA in basal cells, indicating protein synthesis

10 RNA returns to normal

Page 20: Skin graftsw

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 matrix

Proteins direct the behaviour of keratinocytes;

Communication between keratinocytes & fibroblasts.

Page 21: Skin graftsw

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

Page 22: Skin graftsw

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

Page 23: Skin graftsw

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

Page 24: Skin graftsw

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.

Page 25: Skin graftsw

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

Page 26: Skin graftsw

Skin Graft Expansion

• Meshing- covers large area- easier to contour- fluid can drain through holes- cosmetic results less than ideal - various mesh ratio

Page 27: Skin graftsw

Skin Graft Survival

• Meticulous technique• Atraumatic graft handling• Well vascularized bed• Haemostasis• Immobilization• No proximal constricting bandages

Page 28: Skin graftsw

Skin Graft Failure

• Haematoma• Infection• Seroma• Mobility• Inappropriate bed• Dependency• Arterial insufficiency• Venous congestion• Lymphatic stasis• Technical – upside-down