Skin Allografts

Function, Structure, Donor Recovery, Clinical Application

February, 2009

Skin Function

• Skin is considered the largest organ system of the human body– The average adult male has 18 square feet of

skin weighing over 6 pounds• Skin is a remarkably durable structure

– It has an incredible ability to regenerate and heal itself

Skin Function

• The skin provides the following functions for the human body:– Provides a physical barrier to the outside environment– Conserves body fluid by preventing evaporative loss– Provides thermo-regulation/maintains body

temperature– Excretes water and oils– Produces vitamin D in the presence of sunlight– Provides sensations of temperature and touch – Assists in the development of the immune system

Skin Structure

Skin Structure• Epidermis

– The epidermis is the outermost layer containing keratinocytes and melanocytes

• Keratinocytes contain keratin, a protein, which provides a durable mechanical and moisture barrier to protect underlying tissues

• Melanocytes are pigment (color) producing cells and are responsible for skin color

– The epidermis is continually regenerating itself– Although the epidermis is the outermost layer of the

skin, epidermal cells also line the oil and sweat glands as well as the hair follicles

– The epidermis comprises about 10% of skin structure

Skin Structure

• Dermis– The dermis is the innermost layer of the skin

• Collagen, structural protein produced by fibroblast cells

– The dermis is extremely durable and flexible. – Dermis contains blood vessels, hair follicles,

oil and sweat glands, nerve endings– The dermis comprises about 90% of skin

structure

Donor Recovery

Technical Considerations

Types of Skin Recovery

• Split Thickness Skin Grafts (STSG)• Dermal Skin Grafts• Full Thickness Skin Grafts (FTSG)

Skin Recovery: Split ThicknessTypical Cut 0.016

.020.035

Recovery Sites are Mapped

12

34

4

32

1

1

5

Technically Challenging

• Two technicians scrubbed in to recover– One technician operates the dermatome– One technician assists– Key areas to monitor

• Dermatome speed, angle, traction, pressure

Technically Challenging

Technically Challenging

• Very important to keep skin taught

• Best to provide traction behind the dermatome

• Watch angle (45 degrees), speed

• Let the dermatome do the work

Split Thickness Grafts

Clinical Indications

Split Thickness Skin Grafts

Clinical Indications

• The most common injury to the skin is burn– An estimated 130,000 individuals are

hospitalized annually in the United States due to burn injuries

– Many burns are small and will heal completely on their own if kept free from infection

Clinical Indications

• First degree burns are superficial burns and can be quite painful but are generally not considered life threatening. – First degree burns involve only the epidermis– Sunburn is an example

Clinical Indications• Second degree burns or partial thickness burns are more severe

and will involve the epidermis and the dermis– The healing of 2nd degree burns is dependent on how deeply the

dermis is burned. – If the epidermal cells that are found surrounding the hair follicles and

skin glands are not damaged, then they will regenerate and grow a new epithelial (skin) covering.

– If the dermis is burned deeply enough to destroy its internal structures, then new epithelium will not regenerate and grafting may be required.

• Third degree burns or full thickness burns destroy both the epidermis and dermis – May affect deeper tissues such as fat and muscle and connective

tissues. – Most third degree burns will need grafting to replace the lost dermis and

epidermis.

This is not us!

Clinical Indications

Clinical Indications

First Degree Burns are characterized by superficial damage. Skin is red and swollen.

Second Degree Burns are characterized by blisters. They are primarily superficial but may penetrate the dermis.

Third Degree Burns are characterized by a white soft surface and deep tissue damage.

Clinical Indications

• Important Considerations:– Split Thickness skin primarily is used to treat burns

• Potentially for deep, non-healing wounds where a temporary covering is needed while granulation tissue is forming

• Helps promote healing process

– Split Thickness grafts contain very little dermis• Just enough to keep the graft together

– Graft eventually is sloughed off and is replaced• With autologous skin• With a skin substitute (Integra, Apligraft)

Clinical Indications

• Important considerations:– Skin allografts are a temporary wound covering

• Much like gauze or gel• Advantage is allograft skin is effective at maintaining

moisture, reducing pain and potentially reducing chance of infection

– Skin allografts are NOT a grafting material akin to Integra, and AlloDerm, et al

• These are acellular dermal matrix products used in final grafting

• Allograft is split-thickness (primarily epidermis)

Clinical Indications

• Debridement – cleaning

• Excision– surgical removal of burn

injured tissue

Clinical Indications

• Placement of skin graft – The area of the graft is not

moved for five days following each surgery (immobilization period).

– During this immobilization period, blood vessels begin to grow from the tissue below into the donor skin, bonding the two layers together.

Skin, GraftsBenjamin C Wood, MD, Resident Physician, Department of Plastic and Reconstructive Surgery, Wake Forest University Baptist Medical Center; Christian N Kirman, MD, Staff Physician, Department of Plastic and Reconstructive Surgery, Wake Forest University Baptist Medical Center; Joseph A Molnar, MD, PhD, FACS, Associate Professor of Plastic and Reconstructive Surgery, Associate Director, Burn Unit, Wake Forest University School of Medicine

Resources

• http://www.healthatoz.com/healthatoz/Atoz/common/standard/transform.jsp?requestURI=/healthatoz/Atoz/ency/skin_grafting.jsp

• http://www.regionshospital.com/Regions/Menu/0,1640,11334,00.html

• http://www.merck.com/mmhe/sec24/ch289/ch289a.html#sec24-ch289-ch289a-18

• http://www.burnsurgery.org/