Skin graft harvesting tools
The use of split-thickness skin grafts (STSG) is the most common performed procedures to close defects unable to be closed with the simple approximation of the wound edges. The healing of a STSG donor site involves re-epithelialization from the epithelial appendages that are embedded in the dermis and subcutaneous fat.
STSGs are easy to harvest and are taken directly with a knife or with an instrument such as a dermatome. STSGs may be expanded in size using a meshing device or surgical knife.
The following topics are discussed in this chapter:
Components of skin
Classification of split thickness skin grafts
Process of graft take and healing
Indications and contraindications of split thickness skin grafts
Split thickness skin graft donor sites and harvesting the graft
Postoperative care of split thickness skin grafts and management of donor site
Complications of split thickness skin grafts
Preservation of split thickness skin grafts.
2. Components of skin
Skin consists of two layers derived from two different embryonic layers. The thinner, outermost layer is the “
The average thickness of human skin varies between 2 and 3 mm. Skin is thickest in the sacrum, palms, and soles of the feet and is thinnest in the eyelids and in the postauricular area. The epidermis of the face is relatively constant in thickness and measures approximately 150 microns; however, dermal thickness varies considerably. The dermis can be as thin as 200-250 µm in the eyelid and periorbital area, 900-1000 µm in the lip and forehead regions and as thick as 3 mm on the back skin (Gonzalez-Ulloa et al., 1954).
There are five distinct cellular layers of the epidermis. These layers include (from deep to superficial) the stratum basale (stratum germinativum), stratum spinosum (prickle cell layer), stratum granulosum, stratum lucidum, and stratum corneum. The
The dermis consists of two layers: a thin outer
The dermo-epidermal junction of human skin appears as an irregularly, wavy line; the ridges or rete pegs project into the dermis. With aging, these rete pegs diminish and subsequently lead to a decrease in the surface area of the dermal-epidermal junction. Branches from cutaneous arteries form a small vessel plexus within the dermis. The lymphatic plexuses are found in the papillary dermis, directly below the dermal papillary ridges. The skin possesses a rich supply of sensory nerves, which are organized as deep dermal and superficial dermal plexus. These nerves convey sensation from the skin to the brain through specialized receptors for touch (
Sweat glands, sebaceous glands and hair follicles are skin appendages. Sweat glands are found deep in the dermis and even in the subcutaneous tissue. The sweat glands are usually located deeper than the hair follicles; however, hair follicles reach in the subcutaneous fat of the bearded area of the male face. There are two types of sweat glands, apocrine and eccrine. The more numerous eccrine sweat glands are found over the general body surface of humans and open either at the sweat pores on the skin surface or above the opening of the sebaceous gland in the hair follicle walls. Apocrine sweat glands tend to be concentrated in the eyelids, axillae, periumblical area and genital area. The apocrine glands become more active at puberty secrete continuously. The secretions of apocrine glands produce a characteristic odor; however, the eccrine glands are odorless.
Sebaceous glands are derived from the pilosebaceous unit and are commonly associated with hair follicles. The sebaceous glands provide lubricant for the hair and skin and are larger and have more density in the skin of the forehead, nose, and cheeks.
Hair follicles are intradermal epithelial invaginations associated with sebaceous glands and smooth-muscle bundles called erector pili.
3. Classification of split-thickness skin grafts
Skin grafts are classified according to origin and thickness. Skin grafts are classified as
Split-thickness skin grafts (STSGs) are subdivided into
Split-thickness skin graft-thin (STSG-T; 0.008-0.012 in. or 0.2-0.3 mm)
Split-thickness skin graft-medium (STSG-M; 0.012-0.018 in. or 0.3-0.45 mm)
Split-thickness skin graft-thick (STSG-THK; 0.018-0.030 in. or 0.45-0.75 mm)
The STSG-T used by early surgeons such Ollier (1872) and Thiersch (1874) have been replaced by thicker split-thickness grafts (STSG-M, STSG-THK), which include all of the epidermis and a variable fraction of the dermis (Blair & Brown, 1929). Currently, the most commonly used split-thickness graft thickness is between 0.012 and 0.018 inch (0.30 to 0.45 mm) in thickness. The average STSG is cut at 0.015 inch and can be checked by inserting a No.15 blade, which approximates that thickness.
The mesh skin graft was first described by Tanner in 1964 as a method of expanding skin grafts (Tanner et al., 1964). Preparation of the meshed skin graft is performed with a skin graft mesher. The graft is placed on a template and is passed through the device. The most commonly used expansion ratio is 1:1.5, which increases the surface area by 50 percent. Mesh grafts are primarily useful in two situations: (1) when there is insufficient skin; or (2) when a very irregular surface must be covered with a graft where a sheet might not adhere well (Fig. 3c). Also, the drainage of fluid through the slit-like perforations produced by the meshing procedure prevents hematoma formation and permits the graft to be applied to an actively bleeding wound. The expanded graft must heal in between the expansion by epithelization; therefore, the underlying wound may contract significantly.
4. Process of graft take and healing
Grafts initially survive via diffusion, called
Almost all skin grafts are capable of sweating in response to stimulation of the nerves that ingrow from the recipient site. STSGs often have deficient function of sebaceous glands and therefore should be lubricated for three months. Most patients with skin grafts do not obtain completely normal sensation. The recovery of sensation in humans can begin as early as one to two months after surgery, and may be abnormal during the first year. Full-thickness skin grafts appear to achieve better sensation than split-thickness grafts, although the rate of return of innervation is faster in STSGs.
5. Indications and contraindications of split-thickness skin grafts
5.1. Indications of split-thickness skin grafts
Immediate coverage of clean soft tissue defects and accelerated wound healing (Fig. 1a,b.)
Immediate coverage of burn defects and reduced fluid loss from the wounds.
Prevention of scar contracture and enhanced cosmesis in superficial wounds.
5.2. Contraindications of split-thickness skin grafts
Exposed bone without periosteum, cartilage without perichondrium, tendon without paratenon or nerve structures (Fig. 4.).
6. Preoperative considerations
Wounds considered for skin grafting must have a well vascularized and non-infected wound bed. A granulating wound with a healthy appearance usually denotes sufficient nutritional status and overall health of the patient (Fig. 2b, Fig. 3b,). Hypertrophic granulation tissue needs to be either trimmed or flattened in order to enhance graft take and epithelial migration. Epithelial migration at the edges of the granulating surface may be a sign that the wound is ready for application of a skin graft. Serial debridements, culture-specific antibacterial therapy and frequent dressing changes continue to be the mainstay of preparing good recipient bed.
Pretreatment of a wound with vacuum-assisted closure (
6.1. Split-thickness skin graft donor sites and harvesting the graft
STSGs can be taken from any area of the body, including the scalp and extremities (Fowler & Dempsey, 1998). When possible, STSGs should be taken from hidden areas such as the anterolateral thigh and lateral buttock. If STSGs are required for the face, skin harvested from “blush zones” such as the supraclavicular area and scalp is preferable. A thin graft (0.010 inch or less) leaves the hair follicles in the donor scalp and avoids hair growth in the recipient bed. Also, an important source of STSGs is avulsed skin in trauma or surgically removed skin.
|Skin graft harvesting tools|
Various types of dermatomes
Drum (manually operated)
Powered dermatomes (Electric or air);
Battery operated Davol dermatome
Humeca Battery operated dermatome
Zimmer air dermatome
Free-hand knives are manual dermatomes. The large Humby-type knives and smaller Goulian type knives are used for harvesting the STSG manually but provide grafts with irregular edges and grafts of variable thickness (Fig. 6a). Of the powered dermatomes, the Padgett dermatome is lighter and is easy to handle and comes in three widths: small-3 inches wide, medium-4 inches wide, and giant-5 inches wide (Fig.6c). The thickness is determined by turning the setting dermatome knob to the appropriate thickness.
The dimensions of the graft are marked 15-20% larger than the dimensions of the defect. The skin is lubricated with sterile Vaseline ointment to facilitate graft cutting. It is essential to keep the donor area surface flat, taut and stretched, for smooth, uniform thickness during graft cutting. An assistant applies counter-tension on the skin during advancing of the dermatome and graft harvest is performed in a proximal to distal direction. An surgical assistant can pick up the ends of the skin graft with forceps while the surgeon harvests the graft with the dermatome.
6.2. Postoperative care of split-thickness skin grafts and management of donor site
The graft is placed on the recipient bed, trimmed with scissors and fixed with sutures or metal staples. Serous fluid or blood beneath the graft can be a barrier to graft take and a source of infection that will result in graft loss. Multiple small “pie crust” incisions with a ≠11 scalpel blade or fine scissors provide drainage of the fluid or blood beneath the graft. In most cases of skin grafting, the optimal dressing is a bolus or tie-over dressing to ensure contact and immobilization between the graft and the host bed. A circumferential compression dressing and a plaster can be used for immobilization in extremity skin grafts. A tie-over dressing is fashioned by placing sutures around the periphery of the graft and is tied over a piece of fine mesh, ointment impregnated gauze, covered with cotton sheeting or cotton balls. The tied sutures gently press the dressing down onto the skin graft, which in turn is pressed onto the wound bed. This maneuver immobilizes the graft on the wound and prevents hematoma collection. Before the tie-over dressing is applied, the surgeon should ensure that there are no blood clots underneath the graft. The tie-over dressing is left in place for three or four days. After removal of the dressing, small collections of seroma may be evacuated by cutting over the top of the graft and an ointment impregnated gauze dressing applied for another 2 or 3 days. When the skin graft is stable and adherent, antibiotic ointment or another mild lubricating agent is used for three months.
Negative pressure dressing (VAC® therapy) can be used to facilitate skin graft adherence when grafting difficult wounds (e.g. radiated wounds, wounds with irregular or mobile recipient beds and in difficult anatomic locations (Schneider et al., 1998; Scherer et al., 2002) (Fig. 7a,b,c,d.). The VAC dressing is applied to the STSG at 125 mmHg “continuous” mode suction after the STSG is covered with a single layer of non-adherent Chlorhexidine or Xeroform gauze.
6.3. Donor site healing and maintenance
The healing of the donor site occurs by epithelial migration from the epithelial remnants in the dermis such as hair follicles, sebaceous gland, and sweat glands. Epithelial migration also occurs at the wound margins. After harvesting a STSG, the donor site is treated with topical, epinephrine-soaked sponges to reduce bleeding and then a single layer of non-adherent Chlorhexidine or Xeroform gauze is applied to the donor site, followed by a layer of bulky gauze on top of this. The next day, the outer gauze is removed, leaving behind the Chlorhexidine or Xeroform gauze, which can be allowed to air dry; a gentle heat lamp application speeds epithelization. In an area where external contamination is likely, a closed dressing is preferable. The more superficial a STSG is cut, the faster the donor site will heal. The healing of the STSGs donor sites take place over seven to fourteen days (Fig. 8 a,b). Donor sites from which thicker split grafts are cut may not heal for several weeks
Alternatively, donor site are dressed with artificial semi-permeable transparent dressings (e.g. Biobrane®, Opsite® or Tegaderm®) or biologic dressings (e.g. cadaveric skin, sterile irradiated allograft, pig skin, amniotic membrane, cultured keratinocyte grafts) (Fedman, 1991; Voineskos, 2009). Thin STSGs usually leave minimal scarring, whereas the thicker STSGs tend to produce hypertrophic scarring in some patients.
6.4. Complications of split-thickness skin grafts
Graft contraction, graft failure, hyperpigmentation, itchiness and dryness of the graft, durability and growth problems are the most common complications of split- thickness skin grafting.
The causes of split thickness skin graft failure are listed in Table 2. Most skin graft failures can be ascribed to flaws in the recipient bed. Tissue with limited blood supply, such as bone, cartilage or tendon or sites with necrosis or infection do not accept skin graft (Fig. 2a,
Fig. 4). Chronic wounds must be free of pus and should have a healthy, pink to beefy-red appearance with an ideal wound pH of 7.4 or higher. All granulation tissues contain bacteria, but not all are infected. Particular attention should be paid to eliminating
|Causes of Split-Thickness Skin Graft Failure|
|Inadequate recipient bed (poor vascularity)
Inadequate graft fixation and graft shearing
Infection (in particular Streptococcus, which can “eat up” a graft within 24 hours)
Technical errors (too thick or too thin graft, upside-down graft.
Systemic health problems and bad nutritional status
Hyperpigmentation of the skin graft is variable and depends on the amount of pigmentation present in the donor site. Generally, STSGs darken more than FTSGs. Although FTSGs maintain the best pigment match, STSGs often develop significantly dark pigmentation. Sunshine should be avoided for the first six months by use of sun-blocking agents or clothing to prevent long-lasting hyperpigmentation developing in a new skin graft. Both STSGs and their donor sites may scale and remain itchy and dry for many months because the lubricating sebaceous glands have been temporarily devitalized. Lubrication with greasy ointment such as Vaseline, lanolin or cocoa butter helps to replace the lubricating function. Thick STSGs have greater resistance to trauma. Although FTSGs grow successfully in children, the growth of STSGs may be limited.
7. Preservation of split-thickness skin grafts
In order to close skin defects, skin grafts are best stored on its donor site and harvested painless within five days (Shepard, 1972). Skin grafts may also be stored for longer periods, away from the patient, by being refrigerated. Such grafts may be moistened in sterile saline and then placed in a refrigerator at 4 ºC in a sterile Petri dish labeled with the patient’s name and the date of graft harvesting. It may be wise to discard grafts after 8 days, although grafts may be kept for 2 or 3 weeks (Senchenkov et al., 2009).
Long-term storage of autografts and allograft requires special techniques to protect against cell death. Freezing causes tissue death because of concentration within the cell, leaving behind a lethal concentration of salts. Protective agents such as 15% glycerol or 10% dimethyl sulfoxide (DMSO) in Ringer’s solution and storage at -70 ºC with liquid nitrogen help to protect against this type of injury and allow viable skin to be preserved for up to 28 days (Lawrence, 1972). Control of the rate of freezing reduces the damage caused by intracellular ice crystals. The best results were obtained when grafts were slowly frozen and rapidly thawed.
The other technique of storage is
Specialized skin banks have been developed to store large amounts of cadaver skin for treatment of massive burns (Konstantinow, 1991). Standardized techniques for cadaver skin graft preservation use glycerol and rapid freezing with liquid nitrogen (Ninneman et al., 1978). The treated allografts are thawed and used for temporary burn dressings, to be changed every five days. Pigskin xenografts have also been used fresh or frozen for burn treatment.
STSGs constitute the most commonly performed procedures for the closure of skin defects that can not be closed with the simple approximation of the wound edges. When a patient has a full-thickness loss-of-skin defect exceeding 30% of the body area, STSGs taken from the patient are not available in sufficient quantity. Cultured autologous keratinocytes may be used to close larger open wounds in such situations. Unfortunately, the lack of dermis makes the epidermal graft rather thin and fragile. Intensive efforts to develop epidermal and dermal skin substitutes show the greatest potential, at present, for future success.
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