The skin, in the form of a split thickness skin graft (STSG), is the most frequently used donor for tissue coverage. A STSG includes the epidermis and varying amounts of dermis, ranging between 8/1000 of an inch (0.196 millimeters) and 12/1000 of an inch (0.294 millimeters). STSG can be expanded by meshing techniques (1:1.5 to 1:9 expansion) when additional coverage is needed.
Harvesting thicker grafts requires a longer time for donor sites to heal and may preclude that site from repeat harvesting. In addition, thicker grafts in children, the elderly, and debilitated individuals may result in a chronic wound that will require reconstruction.
Advantages
The advantages of STSG include the ability to cover large surface areas with less donor skin and the donor sites may be reharvested once healing is complete. Generally, the donor site can be reharvested in 10 to 15 days. Prior to reharvesting, the patient’s nutritional status must be optimized, and the donor site wound must show evidence of reepithelialization with no evidence of local infection.
Reharvesting together with expansion of the graft by meshing techniques and combination with allograft techniques (sandwich technique: 1:2 autograft covered with 1:4 allograft) allow for coverage of larger defects.
Disadvantages
The disadvantages include fragility, abnormal pigmentation, lack of smooth texture, alopecia, and contractures. When used to reconstruct large burns of the face, STSG may yield an undesirable masklike appearance. The donor site must re-epithelialize and frequently causes significant pain. The lack of dermal element, and subsequently a limited amount of pliability and elasticity, makes split thickness grafting one of the reconstructive options more likely to form contractures in burn reconstruction.
Key technical components
The methods of STSG harvesting have evolved from free-hand with a knife or hand-held dermatome to the use of electrical and air-powered dermatomes. Dermatomes are graded in multiples of 1/1000 of an inch and 5/100 of a millimeter, with most grafts harvested between 8/1000 and 12/1000 of an inch. The harvested graft can be expanded through meshing devices or alternatively used as sheets in cosmetically sensitive areas, such as the face and hands.
- The burn wound is debrided and must be free of a hematoma, exudate, or infection.
- Tumescent infiltration with a local anesthetic and/or epinephrine mixed with saline is performed at the donor and burn wound sites.
- The most common ratios for meshing skin grafts include: 1:1 mesh (mini mesh), 2:1 mesh and 4:1 mesh (with overlying 2:1 meshed allograft), depending on the availability of donor sites.
- The grafts can be secured to the burn with staples, suture, or tissue glue.
- Staples are the fastest method to secure the graft to the wound. The technique is straightforward and the staples are relatively inexpensive. However, they require removal, which is painful, and there is a risk of leaving embedded staples in the wound, which may result in non-healing wounds, infection, and pain.
- Suturing is reserved for small grafts in sensitive anatomical areas in our practice.
- Glue fixation techniques include two types of materials: cyanoacrylates, which are used as an adhesive material to fix grafts to recipient sites, and fibrin based preparations. A review of the use of fibrin glue with skin grafts has shown reduced hemorrhage, improved graft adhesion, and a possible reduction in bacterial wound infections compared with conventional techniques. Two prospective multicenter trials found a significant decrease in hematomas and seromas and improved viability with the use of fibrin glue compared with staples.
- The dressing in contact with the grafted burn should be nonadherent, such as a bismuth-impregnated petroleum based gauze or any other atraumatic non-adherent primary dressing. A gauze or cotton bolster is usually applied to absorb the exudate. An alternative to the bolster or other type of secondary dressing is topical negative pressure therapy (TNP) applied to the grafted burn. Our preference is application of TNP dressings in the immediate post graft period because it helps secure graft take and prepares the area for a splint.
- STSG that are placed in areas that are subjected to shear because of motion (eg, axilla, antecubital fossa, or popliteal fossa), require stabilization with a splint prior to leaving the operating room.
- The donor site is usually managed with topical dressings.
Post-operative management
Two key components of post-operative management of the burn wound include early graft inspection and early mobilization.
- Close-surveillance of the grafted wound facilitates early detection of graft shearing, hematomas, seromas, or any other problems that may affect graft survival. We inspect all grafts on postoperative day two.
- A fundamental component to postoperative management is the initiation of occupational therapy and physical therapy. A careful balance must be achieved between graft protection and preservation of motion in joints. Early mobilization is necessary to preserve function, but excessive early joint mobilization before full graft take or adequate wound healing will shear and destroy grafts by interfering with graft adhesion and compromise the reconstruction.
Immobilization of the reconstructed grafted wound is only necessary until graft take is achieved four or five days postoperatively. This period of rest allows successful graft adhesion and revascularization. Postoperatively, splinting provides for anatomical and functional preservation and minimizes early abnormal scar formation.
STSG survival
The take rate, or survival, of STSG theoretically should be 100 percent providing that wound vascularity is optimal, the wound is free of infection, and the patient has optimal nutrition and infection control. The survival of split thickness sheet grafts and meshed grafts is 95 percent.
There are several local and systemic factors that influence successful grafting, in the same way that wound healing is affected.
Local factors of the burn wound that are associated with decreased STSG survival include:
- Inadequate vascularity, such as exposed unvascularized bone or tendon.
- Inadequate hemostasis, such as a hematoma or seroma under the graft.
- Excessive mobilization.
- Areas of high contact or friction, such as the back, anorectal area, and genitalia.
- Local tissue hypoxia caused by smoking or previous radiation.
Systemic factors that may decrease STSG survival include:
- Advanced patient age. Malnutrition.
- Comorbidities such as diabetes and immunosuppression.
- Steroid use.
Reference: UTD