VI. Skin Grafts Donor Sites (Split Thickness Skin Grafts STSG)

1. The Donor Site

A skin graft is typically a thickness of skin comparable in depth to a partial thickness skin loss, i.e., epidermis and the upper third of the dermis. Typically, the slice of skin is 0.001 to 0.014 inches thick. A split thickness skin graft (STSG) of 0.001 inches typically contains the epidermis and upper third of the dermis, i.e., the papillary dermis. Sufficient epidermal cells remain in the dermis to allow re-epithelialization in about 14 days. A 0.15 inch thickness graft usually contains about half of the dermal layer (or more) which includes a portion of the papillary dermis. Fewer epidermal cells remain and the site heals much slower, similar to a mid to deep dermal burn. Protection of remaining epidermal and dermal elements is essential to allow for proper healing.

The most bioactive portion of the dermis is removed with a STSG, i.e., the papillary dermis. The donor site healing will depend on when bioactive dermal growth enhancing factors are produced on the surface which can then stimulate re-epithelialization. Placement of a tissue engineered wound matrix on the donor site will provide active extracellular matrix components to stimulate healing.

Figure 1: Split thickness skin graft consists of epidermis and upper papillary dermis

Skin graft thickness is also dependent on the thickness of the donor skin. Children and elderly patients have a thinner dermis and therefore a thinner graft, i.e., 0.008 to 0.010 inch, is usually obtained to avoid major morbidity at the donor site. In addition, areas such as inner arms and legs have thinner skin, and adjustments need to be made in the dermatome when obtaining skin grafts fro these areas. 

Healing Time: The usual tome for re-epithelialization of a donor site of 0.010 inch, in depth, is about 14 days in a patient 10 - 50 years old and about 21 days in a toddler or geriatric patient using a typical grease gauze dressing.

Hemostasis: Bleeding from a donor site is similar in amount to that of tangential excision of a fresh, deep dermal burn, i.e., diffuse, puncture, and profuse. Bleeding from a reused donor is even more profuse and again an analogy can be made with a tangential excision of a hyperemic wound. Because blood loss will be substantial, hemostasis at the donor site should be controlled before pursuing wound excision. The ideal situation is the use of two teams, one whose role is to obtain skin grafts and maintain hemostasis. Pressure followed by application of fine mesh gauze or xeroform gauze, again followed by pressure (1 to 2 minutes) is usually adequate to control bleeding.  As with the excised wound, topical thrombin or a diluted epinephrine solution can also be used.

Complications: A number of complications can occur in the donor site. Infection can occur which can result in deepening and possibly conversion of the wound to full thickness. Infection is usually evident from surrounding cellulites. Systematic antibodies as well as topical antibodies are required for treatment. Blistering and continued breakdown are also seen, especially with deep donors or donors in small children or the elderly. Healing usually occurs in time. Hyper or hypo-pigmentation may persist for long periods of time and may be permanent. Hypertrophic scarring is seen especially in dark-skinned persons and with deep donor sites.