Science

Science

Science of Micro-Autografts

Split-thickness skin grafting is a standard reconstructive technique frequently used for acute wounds following surgery or trauma, severe burns, and chronic wounds that fail to heal with nonsurgical management. 1-3 Skin grafts help heal wounds that would otherwise only heal through contraction and epithelialization from the margins (Figure 1). However, skin grafting has been limited by access to a trained surgeon and an operating room, as well as the need for special instruments and general anesthesia.

Unfortunately, for many acute wounds including large burns, limited donor skin can limit skin graft availability and coverage. By meshing or fenestrating a graft intraoperatively using special instrumentation, one can expand split-thickness skin grafts to a maximum of nine times and usually no more than six times. 5, 6

Cultured keratinocytes have also been used for skin replacement. This technique is useful when there are limited donor sites available. This method is effective; however, it is time consuming, expensive, can produce grafts of lesser quality, and requires a two-staged procedure. 7, 8 Cultured allograft cell technology skin substitutes have also become available in various forms containing cultured foreskin fibroblasts and/or keratinocytes. Limitations of these allograft products include cost, limited shelf life, refrigerated or frozen storage, and the need for multiple applications to achieve statistically significant efficacy compared to moist control. 9, 10

Minced skin technology addresses the existing limitations of skin grafting and cultured keratinocytes. Minced skin epithelializes wounds from many spots, rather than just the margins (Figure 2). First introduced by Meek in 1958, 11 the technique preceded the practice of expansion by meshing introduced by Tanner in 1964.12 The Meek method gained limited use due to complicated instrumentation, and the need to orient the pieces with the dermal side down. It provided a maximum expansion of 10 times.

 

In 2002, Svensjo et al. described a technique where it was not necessary to orient the minced skin pieces in any specific direction. 13 Over the past decade, the Meek method has been further refined. Pre-clinical studies of these methods have demonstrated that an intraoperative expansion of 100 times is possible with complete healing of full-thickness wounds in pigs in 14-18 days 14 (Figure 3).

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In a moist environment, the micro-autografts will propagate from the wound bed to the wound surface. Epidermal proliferation will occur from the borders, appendages, and basal layer regardless of particle orientation (Figure 4).

This method has been further developed with innovative devices for skin graft procurement and mincing. Initially, two patients were successfully grafted with minced skin in Sweden, one on an acute leg wound and one for a chronic venous ulcer. 15 Since then, several hundred patients have been treated in the U.S., and a number of clinical cases have been presented as scientific posters on the treatment of challenging chronic wounds, including amputations, venous ulcers, and arterial ulcers. 16, 17 Additionally, Danks et al. reported on a successfully grafted patient with large burns using this methodology. 18

Micro-Autografting Technique

This method is driven by two factors. The first factor is the intraoperative expansion of up to 100 times allowing maximum use of small donor sites. This approach is potentially lifesaving in major burns where a person of normal size (1.75 m2 body surface area) could theoretically have the entire body surface grafted with a piece of skin only 14cm x 14cm. In smaller wounds, the primary advantage is the convenience and flexibility of the technology. The method does not require an operating room or general anesthesia to complete the procedure.

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References

1. Franz MG, et al. Wound Healing Society. Guidelines to aid healing of acute wounds by decreasing impediments of healing. Wound Repair Regen. 2008 Nov-Dec;16(6):723-48.

2. Muhart M, et al. Behavior of tissue-engineered skin: a comparison of a living skin equivalent, autograft, and occlusive dressing in human donor sites. Arch Dermatol. 1999 Aug;135(8):913-8.

3. Boggio P, et al. Is there an easier way to autograft skin in chronic leg ulcers? ‘Minced micrografts’, a new technique. J Eur Acad Dermatol Venereol. 2008 Nov;22(10):1168-72. Epub 2008 Apr 10.

4. Lazarus GS, et al. Definitions and guidelines for assessment of wounds and evaluation of healing. Wound Repair Regen. 1994 Jul;2(3):165-70.

5. Polk HC Jr., Adherence of thin skin grafts. Surg Forum. 1966;17:487-9.

6. Vandeput JJ, Tanner JC, Boswick J. Implementation of parameters in the expansion ratio of mesh skin grafts. Plast Reconstr Surg. 1997 Sep;100(3):653-6.

7. Rue LW, 3rd, et al. Wound closure and outcome in extensively burned patients treated with cultured autologous keratinocytes. J Trauma. 1993;34(5):662-8.

8. Myers S, et al. Transplantation of keratinocytes in the treatment of wounds. Am J Surg. 1995;170(1):75-83.

9. Veves A, Falanga V, et al. Graftskin, A Human Skin Equivalent, Is Effective in Management of Non-infected Neuropathic Diabetic Foot Ulcers. Diabetes Care. 2001;24:290-295.

10. Marston WA, et al for the Dermagraft Diabetic Foot Ulcer Study Group. The efficacy and safety of Dermagraft in improving the healing of chronic diabetic foot ulcers. Diabetes Care. 2003;26:1701-1705.

11. Meek CP. Successful microdermagrafting using the Meek-Wallmicrodermatome. Am J Surg. 1958;96(4):557-8.

12. Tanner Jr JC, Vandeput J, Olley JF. The Mesh Skin Graft. Plast Reconstr Surg, 1964;34:287-92.

13. Svensjo T, et al. Autologous skin transplantation: comparison of minced skin to other techniques. J Surg Res. 2002;103(1):19-29.

14. Hackl F, et al. 100-fold Intraoperative Skin Expansion. American Burn Association. 2009. San Antonio, TX, USA.

15. Personal correspondence with author.

16. Liden B. Split Thickness Skin Micrografts for Wound Healing. Poster at SAWC Spring, 2010.

17. Santrock R, et al. Micrografting for Wound Healing, Wright Medical Technology company poster.

18. Danks RR. Innovations in Caring for a Large Burn in the Iraq War Zone. Journal of Burn Care & Research. July/August 2010. Vol. 31, No. 4.

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