Skin Grafting and Flaps in Burn wounds
Skin grafting is a type of surgery where there is the transfer of a portion of the integument (skin) from the donor site to a host bed from where it acquires a new blood supply to ensure the viability of the transplanted cells.
Advantages of skin grafting
- Skin grafting accelerates healing of burns and other wounds,
- It reduces scar contracture,
- Enhancement of cosmesis,
- Reduction of insensible fluid loss and
- Protection from bacterial invasion.
Classification of skin grafts
Skin grafts are classified into three groups as :
- Split thickness skin graft.
- Full-thickness skin graft.
- Composite grafts. or
Autograft (autogenous graft)
An autograft is transferred from a donor to a recipient site in the same individual.
An allograft is a transplant between genetically disparate individuals of the same species.
An isograft is an allograft between highly inbred strains of animals. Usually experimental transplantation.
Lastly, a xenograft is a graft transplanted between individuals of different species.
What are the Indications for skin grafting?
Skin grafting is indicated in cases of:
- Tissue deficiency following excision of scars, lesions or tumors and to cover defects created after rotating local flaps.
- Scar revision where previous scars are of poor quality or have a poor color match.
- Burn reconstruction as the mainstay.
The choice between full- and split-thickness skin grafting depends on wound condition, location, and size as well as aesthetic concerns.
Split thickness skin grafts
Split thickness skin grafts contain epidermis and a variable amount of dermis. They are usually harvested from the thigh or buttocks.
Full-thickness skin grafts
These types of grafts contain the entire dermis. They are usually harvested from areas with sufficient tissue laxity to permit direct closure of the donor defect.
Composite grafts contain the whole skin and some subcutaneous tissue.
What are the factors to consider when choosing the donor site?
Skin grafts can be taken from any area of the body.
Grafted skin always maintains the epidermal specificity of its donor site.
You will need to consider the scar visibility and color match. Where possible take SSGs from hidden areas e.g. lateral buttocks.
For hand reconstruction e.g. fingertips, the upper inner arm is used as the donor site.
In some cases avulsed or surgically removed skin may be used for SSG.
You should avoid unwanted future hair growth, particularly in children.
Preparation of wound
For graft take, wound bed must be adequate.
This is achieved by management of factors impairing wound healing to ensure good blood supply and asepsis.
What are the causes of graft failure?
Graft failure can result from inadequate or inappropriate graft bed.
Hematoma is the most common cause of graft failure. Risk minimized by; meticulous hemostasis, use of meshed skin graft which allows blood to escape and application of pressure dressing.
Another cause of graft failure is a seroma. Seroma is any collection of fluid under the graft. This reduces the likelihood of it's taking successfully.
Movement such as a shear results in disruption of the delicate connections between the graft and its bed and consequently reduces the likelihood of successful graft take.
Infection. Generally, grafts will not take if the bacterial count of the recipient site exceeds 105/gm of tissue. It is best not to graft if wound infected with beta-hemolytic streptococcus until you've managed the infection.
Another way of managing burnt wounds is by use of flaps. A flap consists of tissues that are moved from one part of the body to another with its own blood supply.
Classification of flaps
Flaps are classified according to the method of movement and tissue composition.
Classification according to the method of movement:
a) Local flaps
Local flaps are based on the near proximity of the recipient site to the donor site. They are applied directly to the defect.
b) Distant flaps
Distant flaps are constructed at a distance from defect and transferred to it.
Classification according to blood Supply
Under this classification flaps are classified to two:
- Random flaps with unknown blood vessel and
- Axial Flap with a known blood vessel
Classification according to tissue composition
Cutaneous flaps consist of skin and subcutaneous tissues
Fasciocutaneous flaps have better viability than random cutaneous but need good anatomic knowledge and surgical finesse and easy to raise. On the other hand, they are quick to execute but leaves donor site deformity.
A muscle flap has an artery delete and paired venae comitantes. The location and size of the dominant pedicle are fairly constant in human muscle. The number and size of the smaller pedicles vary.
The use of muscle as the flap is based on its dominant vascular pedicle. If based on minor vascular pedicles is defined as a distally based flap. This flap is less reliable
Has skin, subcutaneous tissue, muscle and bone
Allows single-stage reconstruction with permanent blood supply
What are the uses of flaps?
Flaps are used to cover exposed Bone, Blood vessel or nerve.