CHAPTER 33 Skin Grafting
Pinch (Patch) Grafting
Pinch grafting (also known as patch grafting; first described in 1872) is a method of treating leg ulcers by grafting small pieces of full-thickness skin, usually harvested from the patient’s medial thigh, to the ulcer site. With pinch grafting, leg ulcer healing rates of 20% to 50% can be anticipated, depending on the cause of the ulcer. Pinch grafting should be considered as an adjunct to conservative therapy and a therapeutic alternative for the inpatient or ambulatory management of leg ulcers. (Chapter 41, Unna Paste Boot: Treatment of Venous Stasis Ulcers and Other Disorders, describes another method for treating lower extremity venous ulcers using the Unna boot.) Pinch grafting requires no special training and no specialized equipment or supplies, but it does require a prolonged period of leg elevation and bed rest after the procedure.
Indications
Pinch grafting can be used to treat any leg ulcer or any other small, slow-healing ulcer of the trunk or extremities. Success rates for pinch grafting are highest for arterial ulcers (50%) and lowest for venous ulcers (20% to 40%). Compared with patients treated with conservative therapy, patients treated with pinch grafting have a shorter time to healing (reepithelialization) and a longer time until ulcer recurrence.
Equipment
Preprocedure Patient Preparation
The patient must be willing and able to comply with postprocedure activity restrictions. The leg ulcer(s) must be clean and must have a granulation base. The ulcer base can be débrided with wet-to-dry saline gauze dressings for 3 to 4 days before the procedure. The relative risks and benefits of pinch grafting should be explained to the patient. All supplies and equipment should be gathered at bedside or in the examination–treatment room. The ulcers should be measured to provide an estimate of the number of grafts needed. The donor site (the proximal medial thigh is preferred) and the skin around the ulcer(s) should be prepared in a sterile manner. Pinch grafting should be performed under sterile conditions.
Technique
Figure 33-1 Local anesthetic (without epinephrine) is injected into the donor site, forming wheals 5 to 10 mm in diameter.
Figure 33-2 Anesthetized skin is grasped with the tissue forceps. Full-thickness pieces of skin 3 to 5 mm in diameter are removed.
Substitutes for Autographs
The mathematics of skin loss is very precise; the body cannot afford to lose too much skin surface area before it is fatally compromised. In some cases there may not be adequate skin to harvest or the patient’s skin condition may be too poor to supply autografts to cover defects. In these cases substitutes are available to cover defects and allow protection and healing.
Early skin substitutes such as Biobrane, which is a collagen-impregnated fabric that imparts a framework for fibroblasts to adhere to on the wound surface and thus accelerate the healing process, have been available for years. Unlike Telfa dressings, where the slick, shiny side of the dressing touches the wound to prevent adherence, with Biobrane the rough, collagen-bearing fabric side is placed next to the wound and left there until it falls off weeks later. With deep second-degree skin loss this is all that may be needed to stimulate healing.
Heterografts such as pig skin may be used to temporarily stabilize and débride large areas of skin loss that may need temporary coverage until autografting can take place with the patient’s own skin.
Synthetic skin has undergone remarkable development from the early days of culturing fibroblasts from the foreskins of circumcised infants, to today’s modern techniques of growing customized skin using stem cell technology. Currently, the major problem with these grafts is their lack of durability and short life span.
Allografting with banked cadaver skin is the mainstay of burn centers today. It is used for covering large, full-thickness areas of skin loss. There is a good supply of this material, but the potential to spread serious tissue-borne diseases always must be kept in mind and could limit general use.
Most of these materials are supplied in sheets, as a mesh, and are ready to be applied using the basic techniques for grafting previously covered. Before using them one must be familiar with all the supplier’s recommendations for use.
Complications
Postprocedure Patient Education and Care
Conclusion
Pinch grafting is a simple therapeutic procedure that may hasten and improve the healing of leg ulcers. The technique is relatively simple, can be performed at the bedside, and requires no special equipment or supplies. This procedure does require a prolonged period of postgraft ambulation restriction. Patients should know about and be prepared for this restricted ambulation. Clinicians should consider pinch grafting as an adjunct to conservative therapy for treatment of leg ulcers, especially when other therapies like the Unna boot have failed. Unna boots do not make a good outer covering dressing for skin grafts because they tend to apply too much compression for optimum vascularization of the new graft.
Full-Thickness and Split-Thickness Skin Grafts
Every primary care physician who manages wounds will encounter full-thickness skin loss that cannot be closed by conventional suturing methods. One of the best ways to solve these full-thickness skin loss problems is through the use of skin grafting techniques. The cutaneous surgeon possessing the basic skills of skin closure can easily master this most useful procedure. Donor skin reduces the size of the defect and speeds healing time. A properly selected and applied graft creates a minimal donor site defect and contributes to good function and cosmetic results.
Indications
Contraindications
note: Defects that are smaller than the size of a dime (1 cm in diameter) will heal well on their own without the need for grafting. If wounds are contaminated with foreign material or are infected, a delay of the grafting procedure will allow for the recipient site to establish granulation tissue that will better support the graft.
Skin Graft Types
Skin grafts are divided into two categories: split thickness and full thickness (Fig. 33-4):
Figure 33-4 Free skin grafts are divided into two main types: split-thickness (A) and full-thickness (B).
Full-thickness grafts consist of the epidermis and the entire dermis. Full-thickness grafts are harvested by sharp dissection with a scalpel, and the thickness of the graft is determined by the region of the body where the donor skin originates.
Split-thickness grafts consist of the epidermis and a variable depth of dermis. Split-thickness grafts take only a part of the dermis, leaving the rest of the dermis at the donor site to regenerate. There are three grades of a split-thickness graft: thin (0.005 to 0.010 inch), medium, and thick. The thickness is varied by the downward pressure the surgeon exerts on the dermatome handle, or by a steeper angle applied to the cutting blade. Mechanical dermatomes are available that have an adjustable gate, or a preset thickness setting, that will determine graft thickness (Fig. 33-5).
Figure 33-5 A, Adjustable-thickness motorized dermatome. B, Adjustment lever on the motorized dermatome that cams the blade up or down to control the thickness of the skin graft. C, Duval battery-powered dermatome with disposable, fixed-depth and fixed-width, detachable head.
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