Autologous Skin Micrografting: A Modified Technique Adopted to the Wound Clinic Setting

INTRODUCTION Skin grafting has been performed for centuries. Transplanting skin using full- or split-thickness skin grafts enables rapid wound closure. However, despite its conceptual simplicity, skin grafting has not entered mainstream outpatient wound care clinics because it requires specialized equipment (eg, skin graft dermatomes and meshers), advanced surgical skills, and an OR. Recently, several commercial kits became available for outpatient use, but they use patented technology, which can be costly. The author developed a simplified skin micrografting technique that can be used by any wound care practitioner because it utilizes only basic instruments and skills and is very inexpensive. HISTORY OF SKIN GRAFTING The earliest known split-thickness skin grafting method was developed by Ollier in 1872. Ollier called his technique “dermoepidermicgrafting.”1 In 1886, Thiersch developed a technique where he cut skin using a razor blade via sharp horizontal incisions to produce thin strips of epidermis and small parts of the dermis. Both methods became known as “Ollier-Thierschgraft.”1 In 1964, Tanner et al2 described a technique for meshing and expanding split-thickness skin grafts (STSGs). Tanner and colleagues’ technique using autologous (from another place on the patient’s body) skin grafts became the criterion standard in skin grafting. Split-thickness skin grafts consist of epidermis and some dermis and are classified based on thickness: thin STSGs are 0.15 to 0.3 mm, intermediate STSGs are 0.3 to 0.45 mm, and thick STSGs are 0.45 to 0.6 mm.1 A typical expansion ratio for traditional mesh grafts is up to 1:3.1 Because STSGs have lower metabolic demands on the wound bed and have better “take” than full-thickness skin grafts, they are commonly used on chronic wounds.3 In 1958, Meek developed a micrografting technique utilizing a Meek-Wall skin graft mesher that allowed a smaller amount of donor skin, so-called “skin islands,” to be transferred to the recipient site, thus increasing the expansion ratio up to 1:9.4,5 The main concepts of his method were (1) split-thickness skin grows from the periphery outward; (2) the smaller the skin graft is, the greater its surface is in relation to its volume; and (3) the ideal for re-epithelializing a denuded area in the quickest manner is to provide the greatest possible growth margin to the area.6 However, Meek’s technique was cumbersome due to the need for epidermal orientation of skin islands, and it was not widely accepted in the plastic surgery community. NOVEL METHODOLOGY The following methodology is a skin micrografting technique that requires only basic instruments. Before grafting, the wound bed must be well-prepared and infection-free. Debride and measure the recipient wound immediately prior to grafting. After obtaining informed consent, cleanse the donor site with topical antiseptic. Mark the area to be harvested with a permanent marker: It should be between 1/4 and 1/5 of the size of the wound to be grafted. Then, inject the donor site with lidocaine and epinephrine 1:100,000 using a 26-gauge needle. The needle length is 25 mm, so smaller donor sites (<9 cm2) can be anesthetized using one or two needle injections. Larger wounds (>9 cm2) may need several dedicated injections in every corner. Using a sterile razor blade, harvest the donor skin. The blade needs to be evenly and minimally bent and moved forward while cutting skin in a right-to-left horizontal motion (Figure 1). Some bleeding must occur to ensure that the depth of the graft collected is at the dermis level. The skin strips are usually between 1 and 1.5 cm in width. They desiccate rapidly and need to be moistened using 0.9% sodium chloride.FIGURE 1: HARVESTING A SMALL SKIN GRAFT USING A RAZOR BLADECut the harvested skin strips into smaller strips using a scalpel (Figure 2). Then, mince smaller pieces from the skin graft strips using forceps and iris scissors or a scalpel (Figure 3). Smaller skin islands are produced by using scissors than by using a scalpel. The skin islands range in size from 1 to 3 mm2; in contrast, Meek islands are a preset 4 mm2 in size.4 Apply the skin islands to the wound and spread them out evenly without any concern for epidermal orientation. Dress the site with a perforated silicone nonadherent dressing and secure it with Steri-Strips. Liberally apply a petroleum jelly-based ointment to retain moisture and then apply a secondary foam dressing. Reapply petroleum ointment with each secondary dressing change, once or twice per week. The skin islands incorporate within 2 to 3 weeks, and the site matures within 1 month. Use compression, immobilization, and offloading, when possible, to prevent migration of skin islands and improve their survivability. Dress the donor site with a petroleum jelly dressing and cover it with a foam dressing. Change the dressing every 2 to 3 days and switch to petroleum jelly ointments at 3 to 4 weeks.FIGURE 2: LARGER SKIN GRAFTS ARE CUT INTO NARROWER STRIPS TO FACILITATE THEIR FURTHER MINCINGFIGURE 3: IRIS SCISSORS ARE USED TO CUT SKIN ISLANDSCASE REPORT The patient provided consent to publish the case details and photographs. A 74-year-old man with a history of chronic respiratory failure, chronic obstructive pulmonary disease, atrial fibrillation, and venous insufficiency of the lower extremities developed a traumatic lower extremity hematoma. He was on home oxygen, chronic steroids, and anticoagulation therapy. When he presented to the wound care clinic, his extremity hematoma was drained, and necrotic tissues were resected. His arterial studies did not reveal peripheral arterial disease, and an Unna boot was placed to facilitate wound closure. The patient’s wound was 3.4 × 2.4 × 0.4 cm and had an uneven base and vertical edges (Figure 4).FIGURE 4: WOUND AFTER HEMATOMA EVACUATION AND SITE DEBRIDEMENTProtracted healing was expected, and skin micrografting was used to expedite healing. Approximately 1.5 × 1.5 cm of skin was harvested from the patient’s shoulder using a sterile razor blade (DebrideBlade; Accutec Inc; Figure 1). It was then minced into small skin islands ranging from 1 to 3 mm in diameter and applied to the wound bed (Figure 5). FIGURE 5: SMALL SKIN ISLANDS ARE SEEN IN THE WOUND BASEFIGURE 6: HEALED WOUND DISPLAYING A CHARACTERISTIC UNEVEN PIGMENTATION OF THE WOUND BASEFIGURE 7: HEALING DONOR SITEFIGURE 8: ROBUST GRANULATION GROWTH ABOVE THE PERIWOUND AREA The wound was dressed with a nonadherent silicon layer (3M Adaptic Touch; Solventum) that was secured with Steri-Strips. Petroleum jelly was applied over the nonadherent silicon layer, the site was dressed with foam (Mepilex Border; Mölnlycke), and an Unna boot was placed. The dressing was changed twice per week, and additional petroleum jelly was applied over the nonadherent silicone layer each time to ensure a moist wound environment. The wound healed within 4 weeks (Figure 6). The donor site healed rapidly as well, with minor excoriations at 6 weeks postharvesting (Figure 7). DISCUSSION Even though the present method includes elements of the Ollier-Thiersch and Meek techniques, its methodology is distinct from both. The author uses a razor blade to harvest skin grafts and then cuts micrografts following Meek’s principle. Unlike Meek, skin grafts are placed on the donor wound bed without concern for their epidermal orientation. Based on the randomness theory, if skin islands are placed arbitrarily on the wound bed, half will be epidermis up, and half will be epidermis down. Theoretically, this would decrease the expansion ratio from 1:9 to 1:4.5. However, some experts believe skin orientation may not be important because skin islands incorporate well despite their orientation under favorable conditions.4 The islands that do not incorporate likely serve as a “compost” for the surviving skin islands by providing growth factors, cytokines, and mesenchymal stem cells. Wounds seen in the wound care clinic are much smaller than typical burn wounds where the Meek technique is commonly used, and the harvested surface area is of lesser concern. Consequently, this methodology used an expansion ratio between 1:4 and 1:5, which is on par or better with the typical expansion ratio of the meshed grafts. An unexpected observation was made that autologous skin micrografting outperformed commercially available placental skin grafts in terms of robust granulation formation in the wound base across all wound types. The author believes that this methodology can replace traditional placental skin grafting in select cases. Potential Disadvantages of this Method The thickness of harvested skin grafts may not be homogeneous. However, because STSGs have significant thickness variability, every piece of skin is minced, and methodology uses a generous expansion ratio, it is likely to be only of a theoretical concern. Because the skin islands have variable sizes, the healed site may show uneven pigmentation. However, in practice to date, donor sites show excellent healing results with only minimal leftover hypopigmentation, if any. Some grafted wounds show such robust tissue growth that granulation fills the void and grows above the periwound (Figure 8). Cautery with silver nitrate typically resolves the issue within 1 to 2 weeks. Finally, skin mincing can be time consuming when dealing with larger wounds. CONCLUSIONS Autologous skin micrografting is an invaluable modality in the wound care clinic. Of the various skin grafting modalities, micrografting has the lowest metabolic demand on a wound bed and is the most suited for the challenges of chronic wounds. The modified approach described herein is effective and easy to learn and does not require any specialized instruments. Procedure tolerability is excellent, as are the postgrafting results. Skin micrografting decreased utilization of commercial cellular tissue products in our practice and has potential to decrease healthcare costs. It belongs in the toolbox of every wound care practitioner. Additional research may shed light on the optimal expansion ratio for different types of wounds and delineate which wound types benefit most from the procedure.