Skin Graft Substitutes, Timing Of

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Principles of Burn Surgery ,

Timing of

Early Surgery, Skin GraftSubstitutes

Dr. Moraya Alqahtani

Dr. Justin Paletz



Objectives

Quick Review

Definition and Rationale for Early Excision

Principles and Methods of Excision

Closure and Skin Graft Substitutes



Historical Perspective

1950’s:

– Rare survival for burns >40%

– Burn wound sepsis less of an issue 1950-70’s:

– normal practice to wait for eschar separation

– wound contraction – increased metabolic rate




1969: Introduction of SSD

– decreased bacterial colonization of wounds

– lower conversion rates to full thickness – increased tendency to watch and wait

– prolonged period to eschar separation

– large unsightly hypertrophic scars




1970’s: Janzekovic Tangential Excision

– performed early before colonization

– patients in better physical condition – improved scar quality

– fewer contractures

– shorter hospital stay

– fewer dressing changes




Value of early excision and grafting

– 1980s - in otherwise healthy subjects

– 20% TBSA – led to shorter hospitalization

– early return to work

– better cosmetic result

– less expenditure




Mortality at the MGH:

– 1974: 24%

– 1979-84: 7% No increase in overall blood loss

No increase in cumulative operating time




Elderly Population (def’n >50yo!!)

– advantages less clear

– Decreased hospital stay – Fewer septic episodes

– Early DONOUR wound closure




Pediatric Population:

– <50%TBSA

NO significant change in 1- length of stay

2-blood requirements

3- mortality

– >50% TBSA decreased mortality.




Mesh Grafting

– greater coverage with available auto graft

– enhanced wound drainage – decreased number of procedures




Other Favourable effects

– no adverse effect on lung function

–animal models suggest earlier return to pre-burnweight

– improved immunologic function



Order of excision

Areas easy and quick to excise: trunk andlegs

Joints and throats Hands and face



Early Excision

Definition:

– Janzekovic- 3-5 days, rational

not yet colonized

definitive tissue damage is established

prior to wound contraction

– Baumer and Henrich - 5-6 days

– Davies- 7 days



Early Excision

“Injured dermisdefends itself poorly against infection, so a

program of slough excision with immediate grafting seems better than focusing on antibacterial measures.” – Z. Janzekovic



Early Excision

Indications:

– deep burns (dermal andsub-dermal)

– significant size – clinical diagnosis

Surgical principles

– preservation of life

– prevention of infection

– conservation of viabletissue

– maintenance of function

– timely closure



Early Excision

Operating Room pitfalls

– Monitoring is difficult

– Unusual, precarious IV sites

– Awkward positioning

– Rapid Blood loss

– Hypothermia



Early Excision

Blood Loss

– Clear pre-operative plan

– Excision prior to wound hyperemia

– Elevation of extremities

– Tourniquet control

– Dilute Epinephrine tumescent fluid

– Epinephrine soaked sponges



Early Excision

Instrumentation

– Humby



Early Excision

Instrumentation

– Goulian-type WeckKnife

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Early Excision

The Procedure (Tangential Excision)

– excise dependant parts first

– knife parallel to the surface

– regular movements

– down to bleeding tissue

– avoid extensive electrocautery

l h i i



early eschar excisionin patients with inhalation injuries

• pulmonary function can be maintained

• the patient is hemodynamically stable

• operating room and body temperatures arekept above 37 °C

• anesthesia time is limited to 2 hours

• no more than 25% of TBSA is excised at one time



Early Excision

Procedure (En Bloc)

– For deeper burns

– Skin and fat excised in one session

– Less time consuming

– Excision down to the natural cleavage plane

– Down to fat or Fascia



Early Excision

Specific Anatomical considerations

– The Scalp

– 10% of TBSA in young children

– Thick, deep appendages

– Initial conservative management

– Ideal donor site (avoid the anterior hair line)



Early Excision

The Face

– Rich sweat and sebaceous glands

– Topical treatment to prevent desiccation (SSD,or polysporin)

– Gentle debridement

– Avoid pressure on nasal alla and oral

commissure – Thick STSG

– Adhering to cosmetic units of the face



Early Excision

External Ear

– Avoid pressure

– prevent chondritis

– Poor blood supply

– Topical Mafenide acetate

– Close any remaining wounds at three weeks



Early Excision

Occular Adnexa

– Evaluate for corneal injury

– No early intervention (tarsorraphy etc)

– Acute lid release for ectropion



Early Excision

The Neck

– Full thickness - early excision and thick sheetauto graft

– conforming neck splints

– early neck release in the acute phase if airwayis compromised



Early Excision

Hands

– Initial 72hours

perfusion (serial examination)

Full ROM bid

Splint in position of safety with 1st web space open

Early excision and sheet grafting

Goal: function consistent with ADL’s



Early Excision

Genital Burns

– Spontaneous sloughing

– Redundant scrotal skin very forgiving

– Meatal stenosis may require meatotomy



Wound Closure

Strategies

– Skin Grafting

– Non-cellular matrix

– Combination of matrix and cell culture

– Epidermal cell culture to replace epidermisalone.



Wound Closure

Techniques

– unmeshed sheet grafts

– Meshed grafts (1:1, 1.5:1) non expanded

– Meshed grafts (4:1) with wide expansion



Wound Closure

The donor site

– Numerous techniques

– Scarlet red

– Opsite/Biobrane

Heals by epithelialisaton from appendages

– faster in thin graft donor areas

– dermis heals with scar formation

– deeper sites may exhibit hypertrophic scarring



Burn Wound Closure

Skin Grafts

Graft substitutes



Many skin substitutes are in development

Some of these are designed as suitable materialswith which to facilitate early burn wound excision

regimes Others are targeted at chronic wounds.



Wound Closure

Criteria for wound closure materials

– nontoxic, antiseptic, non inflammatory – non antigenic barrier to bacteria

– tissue compatibility

– normal rates of water and heat conductivity

– immediate uniform and intimate adherence

– elasticity, durability

– malleabile

– growth potential

– long term mechanical and cosmetic function

– low cost



Differences in the application and expectedperformance of skin substitutes

Materials that are applied for short periods thenremoved, to stimulate autologous healing

Cell free material that encourage colonisation by

autologous cells, to stimulate new skin formation Cell containing skin substitutes: to provide

immediate functional replacement



Wound Closure

Goals:

– reestablish barrier (epidermis) to preventbacterial invasion and evaporative water loss

– reconstitute the dermis to providedurability,pliability and acceptable cosmesis

Two Approaches:

– wound coverage – wound closure



Skin graft substitutes

Categories of engineered skin substitutes withexamples



Skin substitutes for wound cover

Biosynthetic materials: Dermagraft and Transcyte

unprocessed skin products, such as xenograft andhuman cadaveric and living allografts

Cultured allogeneic keratinocytes

Apligraf (Graftskin )

Dermagraft



Biobrane

a bilaminatemembrane

As the wound heals,

Biobrane separates,and can readily bepeeled away from thesurface

donor sites andsuperficial partial-thickness burns withinthe first 6 h of injury

clean wounds



Transcyte

collagen-coated nylon meshin Biobrane is seeded withneonatal fibroblasts

fibroblast-seeded Biobrane

was known as Dermagraft- inner biological layer are

allowed to grow for 17 days,during which they produce

fibronectin, type I collagen,proteoglycan and growthfactors.

it adheres rapidly to a viable



Cultured allogeneic keratinocytes

dressing in chronic open wounds, such as legulcers

survival is assisted by the absence of detectable

Langerhans cells, lymphocytes, melanocytes andendothelial cells (which all express HLA class IIantigens) at the time of transplantation



Apligraf (Graftskin )

Apligraf (Graftskin ) – living skin equivalent, human skin

gel of type I bovine collagen with living neonatal

allogeneic fibroblasts with an overlying cornifiedepidermal layer of neonatal allogeneickeratinocytes.

primary role is as a treatment for chronic ulcers.



Dermagraft

cryopreserved living dermal structure, cultivatingneonatal allogeneic fibroblasts on a polymerscaffold

used beneath meshed split-skin grafts on fullthickness wounds

This could represent a useful means of replacinglost dermal tissue where thin split-skin graft wouldbe desirable



Skin substitutes for wound closure

Alloderm

Integra

Cultured autologous keratinocytes (Epicel)

Laserskin

Cadaveric allograft



Alloderm

processed human cadaveric skin

Removed epidermis, extracted dermal cells

template for dermal regeneration

good take rates

reduce subsequent scarring

allowing grafting of an ultra-thin split-skin graft as

a one-stage procedure



Integra

most widely accepted synthetic skin substitute

bilaminar structure

The median ‘take’ was 85%

two-stage procedure, with a minimum interval of 3weeks between the application of the Integra andthe split-skin grafting

relatively expensive



Wound Closure

Dermal Matrix Strategy

– Integra: totally artificial, acellular bi-layer

– silastic upper layer porous to allow vapor loss

– lower highly porous collagen and proteoglycanmatrix

– allow for neo-dermis formation

– STSG (0.002-0.004 inch) or epidermal cellcultures



Wound Closure

Dermal Matrix Strategy

– take -80%

– early donor site healing (4 days earlier)

– less hypertrophic scarring



Cultured autologous keratinocytes

be grown in vitro and then applied to wounds the take of cultured epithelial autografts depends

on the wound bed they are expensive skilled labour and quality control, 3 –5 weeks to produce 1.8m2 confluent sheets of

cells from a 2 cm2 biopsy fragile sheets Blistering, infection, and contractures.



Wound Closure

Suggested Clinical Indications for CAE

– burn injuries >90% broad

– 70-90% more limited

– <70% no clear indication



Laserskin

Upside-down membrane delivery systems

membrane delivery system created from a laser-perforated derivative of esterified hyaluronic

Sprayed cell suspensions

The wound is reported to heal faster and to be ofsuperior quality where cells were sprayed.



Composite epidermal –dermal skin substitutes

combining keratinocytes with some form of dermalmatrix,

improve techniques for keratinocyte transfer

influence epidermal attachment, growth anddifferentiation.

Increase Collagen VII



Collagen –glycosaminoglycan matrix

acceptable take, with basement membraneformation within 9

rapid wound closure

More recently, in burn patients, cultured skinsubstitutes have been successfully applied to

vascularised Integra for the closure of excised full-thickness wounds



Wound Closure

Composite Materials Strategy

– Allograft skin with cultured autologousepidermal cells (Cuano et al.)

– Gelled collagen seeded with epidermal cellsand fibroblasts (Bell et al.)

– Collagen-glycosaminoglycan (CAG) matrix with

epidermal cells and fibroblasts – Dermal matrix from fibroblasts on vicryl mesh



Skin Grafts



Skin Grafts

Synthetic Grafts (INTEGRA)

- formed by layer of collagen-chondroitin-6-sulfate (dermis) adherent to silicone (epidermis)

- regenerates dermis

- prevents fluid loss with immediate wound closure

- no rejection and biodegradable

- no risk of disease transmission

- not perfect, can still fail

i.e. if contaminated, pathogens flourish easily and graft fails in a few days

Skin Graft Substitutes, Timing Of

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