Skin Grafting: What You Need to Know from A to Xenograph
A thorough understanding of the clinical and coding sides helps determine correct skin grafting codes.
By Linda Martien, CPC-EDS, CPC-H
In its most basic sense, skin grafting is the transplantation of skin and, occasionally, other underlying tissue types to another location of the body. The technique of skin harvesting and transplantation was initially described approximately 2,500 to 3,000 years ago with the Hindu Tilemaker Caste, in which skin grafting was used to reconstruct noses that were amputated as a means of judicial punishment. More modern uses of skin grafting were described in the mid- to late-19th century (pinch grafts), followed by split-thickness graft in 1872, and the full-thickness graft in 1875.
Skin grafting is a surgical procedure by which skin or skin substitute is placed over a burn or nonhealing wound to permanently replace damaged or missing skin or provide a temporary wound covering. For the purposes of this discussion, we will address split-thickness and full-thickness skin grafts.
The skin is the largest organ of the human body. It consists of two main layers: The epidermis is the outer layer, sitting on and nourished by the thicker dermis. These two layers are approximately 0.04-0.08 inches (1-2 mm) thick. The epidermis consists of an outer layer of dead cells (which provides a tough, protective coating) and several layers of rapidly dividing cells called keratinocytes. The dermis contains the blood vessels, nerves, sweat glands, hair follicles and oil glands. The dermis consists mainly of connective tissue, primarily the protein collagen, which gives the skin its flexibility and provides structural support. Fibroblasts, which make collagen, are the main cell type in the dermis.
Determine the Graft Type
Skin for grafting can be obtained from another area of the patient’s body, called an autograft, if there is enough undamaged skin available, and if the patient is healthy enough to undergo the additional surgery required. Alternatively, skin can be obtained from another person (donor skin from cadavers is frozen, stored and available for use), called an allograft or from an animal (usually a pig), called a xenograft. Allografts and xenografts provide only temporary covering — they are rejected by the patient’s immune system within seven to 10 days and must be replaced with an autograft at that point.
One type of autograft is a split-thickness skin graft. This type of graft comprises mainly the epidermis and a little of the dermis, and usually heals within several days. The wound must not be too deep if a split-thickness graft is going to be successful, since the blood vessels that will nourish the grafted tissue must come from the dermis of the wound itself.
CPT® gives us codes from the 15100-15136 range for split-thickness autografts. These codes denote grafts of epidermis and dermis to the body in increments of 100 square cm for adults and by percentage of total body area for infants and children. It is important to note that the “dividing age” between children and adults for this purpose is 10 years old. Coders will use this entire range of codes, even though it describes the autografts separately from the dermis, epidermis and split-thickness grafts. It is also important to note that when the physician’s procedure note includes grafting that involves the eyelid, the coder must also look to 67961 and the codes following it.
A full-thickness graft involves both layers of the skin. Full-thickness autografts provide better contour, more natural color and less contraction at the grafted site. The main disadvantage of full-thickness skin grafts is that the wound at the donor site is larger and requires more careful management. Often, a split-thickness graft must be used to cover the donor site.
The CPT® codes for full-thickness autografts include 15240-15261. These codes do not differentiate between adults and infants or children. They are divided into groups according to anatomic site, such as forehead, cheeks, chin, mouth, neck, axillae, genitalia, hand and/or feet (15240-15241) and nose, ears, eyelids, and/or lips (15260-15261). These codes are further divided into areas of equal to or less than 20 square cm, or greater than 20 square cm.
The codes for full-thickness autografts may also be described as “free skin grafts,” as opposed to tissue transfers. This means these autografts are lifted free from the donor site and moved to the recipient site as a separate unit. There is no tissue transfer or rearrangement in these procedures. The closure of the donor site is a separate procedure and should be coded as such. Remember that skin grafts are always coded to the recipient site and not the donor site.
A composite skin graft is sometimes used, consisting of combinations of skin and fat, skin and cartilage, or dermis and fat. Composite grafts are used where three-dimensional reconstruction is necessary. For example, a wedge of ear containing skin and cartilage can be used to repair the nose. These types of grafts would also be considered full-thickness.
Allograft: Tissue that is taken from one person’s body and grafted to another person’s.
Autograft: Tissue that is taken from one part of a person’s body and transplanted to a different part of the same person’s body.
Collagen: A protein that provides structural support; the main component of connective tissue.
Dermis: The underlayer of skin containing blood vessels, nerves, hair follicles, and oil and sweat glands.
Epidermis: The outer layer of skin consisting of a layer of dead cells that perform a protective function and a second layer of dividing cells.
Fibroblasts: Cells found in connective tissue that produce collagen.
Keratinocytes: Cells found in the epidermis. The keratinocytes at the outer surface of the epidermis are dead and form a tough protective layer. The cells underneath divide to replenish the supply.
Xenograft: Tissue that is transplanted from one species to another (e.g., pigs to humans).