MEEK MICROGRAFTING TECHNIQUE AND ITS USE IN THE TREATMENT OF SEVERE BURN INJURIES AT THE UNIVERSITY HOSPITAL OSTRAVA BURN CENTER

INTRODUCTION

Insufficient autograft donor site availability is a limiting factor in the surgical management of extensive burns and early wound closure after necrectomy. Surgeons have, therefore, long sought new and enhanced methods of skin transplantation that have already been proven in clinical practice. In 1958, American physician Cicero Parker Meek at the Aiken County Hospital in South Carolina published a new skin graft technique, which he called “micrografting”.¹ This method was novel in that small skin grafts were not prepared manually, but rather with the “Meek-Wall microdermatome” device that he had developed in cooperation with engineer S.P. Wall. Between 1958–1965, Meek published 4 additional papers further describing his micrografting technique and its results.^2,3,4,5 In 1963, Meek and Wall patented their device in the USA as the “Microdermatome”. Despite promising results, however, Meek’s method did not receive wider application at that time due to high hopes for the mesh skin graft technique (introduced in 1964), which was simpler and less costly to perform. Advances in resuscitation and complex intensive care for burns led to increased survival of patients with severe extensive burns. With increasing frequency, situations arose (and continue to arise) wherein skin grafting with meshed grafts was insufficient due to lack of donor sites. In the 1990s, Meek micrografting was “rediscovered” and refined by Dutch surgeons Rudy Hermans and Robert Kreis in Beverwijk, The Netherlands.⁶ In collaboration with engineers from Humeca⁶, they introduced the “Humeca dermatome” into clinical practice. At present, the Meek technique is most commonly employed in cases of extensive thermal trauma with insufficient donor sites.⁷ The method provides effective and aesthetic results⁷ which, at a minimum, correspond to results achieved with meshed skin grafts.^8,9 The Meek technique was first used at our facility in 2013 in a patient with extensive burn trauma to 91% of the total body surface area (TBSA). In this paper, we present our results and experience pertaining to the healing process, micrograft engraftment, and subsequent scar development.

MATERIAL AND METHODS

Patient sample and surgical approach

Between March 1, 2013 and September 30, 2015 the Meek technique was used in 4 adult patients (3 men and 1 woman; mean age 40 years) with extensive burn injuries. In all 4 patients, the burns were caused by fire; 3 cases resulted from an explosion and 1 case was a suicide attempt. The average burn size was 75% TBSA with 36% TBSA third-degree (Table 1). The mean hospitalization was 129 days (range 83–194), of which 79 days (range 62–99) were spent in an intensive care unit. Three patients required artificial ventilation, escharotomy in areas of deep circumferential burns, and tracheostomy. The mean duration of artificial ventilation was 69 days (range 61–74). On average, necrectomies were performed on 30% TBSA (range 8.5–65). Of these, fascial necrectomy was performed on about 12.8% TBSA; tangential necrectomy on about 12.8% TBSA; and chemical necrectomy, using with 20% or 40% benzoic acid in an ointment, on about 4.6% TBSA. In 3 patients, skin autografts were immediately transplanted to the area after necrectomy or abrasion. In 1 patient, an Integra^® (Integra Life Sciences Corp., USA) biosynthetic skin substitute was used first on an area of about 17% TBSA, and was then followed by subsequent autografting. In all 4 patients, the Meek technique was used for the greater part of autografting and smaller remaining sites were covered with meshed dermoepidermal grafts (see Table 1). A total of 14 operations were performed with the Meek micrografting technique, during which an area approximately equal to 2 m² was gradually transplanted.

Postoperatively, each patient’s healing process was monitored every 2–3 days during dressing changes in the operating room. Clinical estimates were conducted via visual assessment of the Meek micrograft engraftment percentage and epithelialization progress between autograft islands. Engraftment was confirmed on the postoperative day (POD) during which micrografts achieved complete adhesion to more than 90% of the transplanted site with no secretions and clear vitality. Epithelialization progress between micrografts was clinically evaluated with the following three-level scale: 1) incipient epithelialization, 2) proliferative epithelialization, and 3) total epithelialization. During the subsequent course of 1 year after healing or longer, scars were monitored for the development of hypertrophy and scar contractures. Red or reddish rigid scars rising above the surface of healthy surrounding areas were assessed as hypertrophic.

Meek micrografting preparation procedure

1. Dermoepidermal autografts (DEAs) are harvested via electrodermatome (preferred) or skin graft knife (e.g. Watson or Goulian).
2. DEAs are placed on a cutting surface, superficial side up.
3. Special 42 x 42 mm cork plates are placed on the DEA cutting surfaces.
4. DEAs are cut using a scalpel to precisely duplicate the shape and size of the cork plates. Micrografts can be prepared with very small DEAs (or even DEA remnants), thereby achieving maximum efficiency in the use of harvested tissue.
5. DEAs on cork plates are placed in a special cutting block, the upper side of which has parallel holes for 13 dermatome knives along the length, through which skin grafts are linearly sectioned in parallel. The graft-covered cork plate is then rotated 90° and the knives linearly section the skin graft once more. This produces a total of 196 (14 cuts x 14 cuts) small autograft islands that are 3 x 3 mm in size (Figure 1).
6. Micrografts are sprayed with Leukospray^® (an adhesive specially designed for this purpose) and applied to prefolded bilayered gauze (polyamide fabric top layer + aluminium foil backing) that will enable the appropriate degree of expansion. Once applied, the micrografts are manually pressed onto the gauze using a special instrument, which results in their adhesion.
7. Micrograft backing gauzes are then wrapped in saline-moistened gauze to prevent drying out prior to their transplantation.
8. Shortly prior to wound bed application, the bilayered backing gauze is gently separated from the cork plate. The prefolded gauze is then firmly pulled in 2 mutually perpendicular directions to achieve the desired micrograft expansion. Possible expansion ratios include 1:3, 1:4, 1:6, and even up to 1:9. Expansion ratio is determined by the number of available donor sites and according to local area findings. The fewer the number of available donor sites, the greater the required degree of expansion.
9. Expanded micrografts are applied to the wound bed. The aluminium foil layer is removed from the backing gauze, while the polyamide fabric layer with the adherent autograft islands remains. The edges of the polyamide gauze carrier are then secured with metal staples (Figure 2).
10. The gauze carrier remains in situ for 7–10 days (in cases of uncomplicated healing). The metal staples are then removed and the gauze is removed. At this stage, the micrografts typically show engraftment with the first signs of incipient epithelialization between them.

Statistical method

Due to the small patient sample and small number of operations, the study statistically corresponds to a small selection and the obtained data was evaluated using conventional descriptive statistical methods.

RESULTS

Micrograft engraftment and epithelialization of the wound bed between islands without the need for reoperation was observed over an area of about 1.73 m². Reoperations in areas with insufficient micrograft engraftment (i.e. areas without pre-epithelialization of the wound bed between islands), were performed on a total area of 0.27 m². Thus, 86.5% of autografts performed with the Meek technique were successful. In terms of relative value, nearly 50% of non-engraftment involved a single patient with partial micrografting failure due to non-viable (the cause for which was uncertain) Meek micrografts. Postoperative healing showed only 10% of the micrografts to be viable, and with too low a density to produce pre-epithelialized areas. Therefore, retransplantation was required over about 6% of TBSA. In another patient, 1 of 3 micrograft transplant operations showed only 50% engraftment and epithelialization between islands. This was caused by a pseudomonas infection that was verified with bacterial culture. In half of the cases, areas were transplanted immediately after necrectomy, and necrectomies were either tangential (4), fascial (2), or chemical (1). The remaining half of transplants were deferred in areas with wound base granulation. The lowest success rate of Meek micrograft engraftment and epithelialization progress was clinically apparent in areas transplanted immediately after fascial necrectomy (22.5%). The highest success rate of Meek micrograft engraftment and epithelialization progress was observed in areas with deferred transplantation, i.e. areas with wound bed granulation (82%). The shortest interval between necrectomy and transplant surgery was 16 days. The longest interval (28 days) occurred in 2 transplant procedures, during which necrectomy was followed by Integra^® synthetic skin substitutes, which required a waiting period for the neodermis to form. During the interval between necrectomy and transplant operation, wound beds were regularly rebandaged and dressed, most commonly with COM^® synthetic dressings (VUP Medical, Czech Republic), or Xe-Derma^® xenografts (MEDICEM International CR, Czech Republic). Wound beds dressed with Integra^® were treated and covered with Betadine ointment (Egis Pharmaceuticals, Hungary), impregnated Xeroform gauze, and compresses with antiseptic solutions (Prontosan^®, B. Braun Medical, Czech Republic; Microdacyn^®, Oculus Innovative Sciences, The Netherlands).

Unambiguous micrograft engraftment was clinically evident as early as the 12^th POD (range 12–18). Epithelialization between islands, the progress or speed of which was also monitored, occurred simultaneously with micrograft engraftment. An autograft expansion ratio of 1:4 was used in 7 transplant operations and total epithelialization between islands was apparent, on average, by the 16^th POD (Table 2). An autograft expansion ratio of 1:6 was used in 6 operations and total epithelialization between micrografts was achieved, on average, on the 17^th POD. An autograft expansion ratio of 1:3 was used in 1 operation and total epithelialization between autograft islands was observed on the 17^th POD.

In terms of microbiological surveillance, areas were regularly examined for indications of infection. In 1 patient, a clinically apparent and microbiologically verified infected area resulted in a significant portion of Meek micrograft non-engraftment. On the 7^th POD, a Pseudomonas aeruginosa infection was cultured at a level of 1x10⁵ per 25 cm². This area only achieved a 35% engraftment and subsequently required retransplantation over an area of about 6% of TBSA, which corresponded to half of the transplanted area.

Three patients were monitored for hypertrophic scar formation and scar contractures for a period of at least 1 year after healing (1 patient relocated abroad permanently after healing and thus was not monitored during the follow-up course of treatment). The 3 monitored patients developed scattered areas of hypertrophic scarring on the neck, trunk, and extremities both in areas with transplanted Meek micrografts, and areas with transplanted meshed grafts. Hypertrophic scars were treated with a combination of elastic pressure dressings, pressure massage, topical applications, and rehabilitation. Two patients also underwent laser treatment as a part of their scar therapy. No patients developed scar contractures that required reconstructive surgery in areas that had been transplanted with Meek micrografts. One patient required surgery for scar contractures on the neck in an area where dermoepidermal autografting with meshed grafts had been performed. The scars were released with multiple Z-plasties. Of the areas with transplanted Meek micrografts, 1 patient developed slight scar contractures in each axilla with mildly restricted upper limb elevation. During the course of conservative therapy, the left axilla scar contracture was released and a mild contracture persisted in the right axilla (the latter of which restricted right arm elevation to an insignificant degree.) The patient was offered surgical correction but refused because they did not consider the restriction to be serious. Another patient developed mild contractures in the 2^nd to 4^th interdigital spaces on both hands but responded well to laser therapy and the contractures gradually subsided without the need for surgical treatment.

DISCUSSION

The Meek technique was rediscovered in the 1990s in conjunction with advances in intensive care medicine for extensively burned patients and the need for efficacious surgical treatment. When compared with other skin graft methods, the Meek technique is associated with better viability^2,10,11 and, therefore, better autograft engraftment, which ultimately shortens hospitalization and leads to greater economic efficiency of treatment.⁶ When using comparable expansion ratios, epithelialization occurs faster in comparison with the more frequently used mesh graft method due to the smaller distances between skin micrografts.⁶ The distance between individual Meek islands when using a 1:9 expansion ratio is 8–9 mm compared with 11–12 mm when using an expansion ratio of 1:6 with meshed grafts (Hsieh, 2008). Despite higher expansion, the distance between skin graft edges in Meek micrografts is smaller than that used in meshed grafts⁶ and is directly associated with faster epithelialization in areas with transplanted Meek grafts.^{7, 8,12,13}

Total epithelialization between Meek autografts is typically achieved within 3–4 weeks after transplantation, depending on the expansion used.^7,8,14 On average, total epithelialization was evident in our patients on the 16^th POD when a 1:4 expansion ratio was used, and on the 17^th POD when expansion ratios of 1:3 and 1:6 were used. However, the expansion ratios used in our patients did not significantly impact the rate of epithelialization between micrografts. Total reepithelialization has been described 1 month after surgery when using a micrograft expansion ratio of 1:9.⁷ We have not yet used this expansion ratio in our practice. If we evaluate the epithelialization rate in terms of transplantation timing (i.e. areas transplanted immediately after necrectomy vs. areas with deferred transplantation due to base granulation), differences in epithelialization rates between micrografts were minor and clinically insignificant. Likewise, there was no apparent correlation between the epithelialization rate and the size of the transplanted area. Engraftment using the largest possible number of Meek micrografts was vital to satisfactory healing in the context of the patient’s overall condition. Some sources indicate that use of a 1:6 expansion ratio or greater requires that Meek autografts be covered with an allograft overlay.¹⁴ In our clinical practice, we used a 1:4 expansion ratio most often, which was a total of 8 times. A 1:6 expansion ratio was used 5 times, and a 1:3 expansion ratio was only used once. Regardless of the expansion ratio, we performed the Meek technique without the use of xenografts or allografts and our patients showed satisfactory healing. The observed rates of Meek autograft engraftment and subsequent epithelialization correspond to current published data.^8,9,12 Based on our experience, we can confidently state that Meek micrografts with a 1:6 expansion ratio do not require xenograft or allograft overlays to ensure satisfactory healing.

In cases of transplant area healing complications, the most common cause of autograft non-engraftment is infection. Some studies have shown that Meek micrografts are more resistant to infection than meshed grafts.^7,8 It appears that micrografts are more resistant to infection than meshed grafts because, unlike the later, they are not connected by skin graft bridges. Therefore, should infection occur, only a specific portion of the micrografts in the affected area are at risk of uncertain vitality. Micrograft engraftment outside of these areas often takes place without complication. Successful Meek micrograft engraftment with a 1:6 expansion ratio has also been described in infected wound areas.⁷ Micrograft non-engraftment caused by infection, which results in the need for retransplantation of the affected areas, is a relatively infrequent complication. In our sample, it only occurred once. Method failure also occurred only once in another patient when the Meek grafts we prepared proved to be non-viable. We were unable to precisely determine the cause of this failure, but it can be assumed that human error during micrograft preparation was to blame.

In our view, a significant advantage of the Meek technique was the precise approximation of the chosen expansion dimension. It is possible to preoperatively calculate and plan transplant options for individual stages of surgery and, in uncomplicated healing, the rate of epithelialization and healing can be predicted quite well. Thereby, management of overall treatment becomes more easily guided and more precise. The disadvantages of micrografting are reported to be greater economic demands, longer graft preparation time, and greater demands on medical personnel.¹⁴ While the greater financial burden of Meek micrografting cannot be disputed, our experience leads us to believe that the issues of longer graft preparation and higher demands on medical personnel are debatable. Meek dermoepidermal autografts are harvested in the same manner as with mesh grafting; the difference lies in the potential to even use very small areas of healthy skin with the Meek technique. Micrograft preparation at our facility was performed by only 1 surgeon who used an electric Humeca dermatome. Perioperative nurses sprayed the graft islands and followed the exact time interval until the adhesive dried. Necrectomy, or abrasion of granulated areas when using deferred transplantation, were conducted in parallel with micrograft preparation. Necrectomy and micrograft preparation durations were approximately the same; at the time of necrectomy completion, micrografts were usually fully prepared for transplantation. At the time of granulation abrasion completion (which is less time-demanding compared to necrectomy), micrografts were only partially prepared; further micrograft preparation was carried out in parallel with transplantation and it was often necessary to wait. Meek micrografts were always prepared on a series of 2 gauze carriers since the cutting machine (in which grafts on cork plates are sectioned into square autograft islands), only has space to insert 2 cork plates at a time.

It takes approximately 15 minutes to prepare 1 pair of micrografts. Nearly half of this period is spent waiting for the Leukospray adhesive to dry (7 minutes). While the adhesive dries, the surgeon is already preparing the next pair of micrografts. The first pair of micrograft backing gauzes is ready for transplantation in 15 minutes; and each additional pair follows at regular intervals of approximately 8 minutes. With precise knowledge of this method, the time-demanding preparation of Meek micrografts is not a limiting factor that prolongs surgical time to the point of endangering the patient.

A great advantage of the Meek technique is that autograft preparation can be performed with very small skin grafts of highly diverse shapes that are virtually impossible to use in mesh grafting; this advantage is due to Humeca dermatome sectioning and expansion, which ensures highly efficacious use of donor sites. This allows surgeons to harvest and use autografts from unburned areas from virtually any location and size. The Meek technique is therefore the most suitable method for extensive burn trauma with insufficient donor sites, because it enables harvesting and precise expansion from very small areas of healthy skin. The Meek technique enables higher quality transplantations in more extensively burned areas compared to mesh grafting because meshed grafts are rather problematic in small areas of skin, which results in unequivocally lower success rates compared to Meek micrografting. Thanks to the bilayered gauze, manipulating highly expanded Meek micrografts is not complicated; the graft islands are virtually untraumatized during handling and the gauze enables precise graft placement and fixation. By contrast, manipulation of widely meshed dermoepidermal grafts is far more difficult; the grafts are very delicate and always traumatized, to a certain extent, during removal from the paper carrier (which may impair the viability of grafts). Wide expansion of meshed grafts with ratios of 1:3 or higher requires use of the sandwich-technique (based on the principle of mixed transplantation) to stimulate healing and protect the grafts. Meshed autografts are covered with meshed non-expanded xenografts. In our experience, transplantation with the sandwich-technique was comparable to the Meek technique with respect to surgical time, but it was more demanding in terms of implementation.

The subsequent course of scarring has only been mentioned sporadically in previous works. Authors have reported that no significant functional or aesthetic differences have been observed when comparing scarring after using Meek and mesh grafting techniques.^7,8,9,14 Three of our patients underwent follow-up monitoring of scar maturation and development during the course of at least 1 year after transplantation, and this monitoring is still on-going. Scattered areas of hypertrophic scarring occurred both in Meek and meshed transplant areas. None of the monitored patients developed severe scar contractures that required reconstructive surgery in areas with Meek micrografts. One patient required surgical treatment for a scar contracture on the neck in an area where dermoepidermal mesh autografting had been performed. In our group, the need for surgical scar contracture release in areas that had been transplanted with meshed grafts was relatively high despite the use of combination therapy (e.g. rehabilitation, elastic pressure dressings, pressure massage, and topical treatment). At our facility, laser therapy significantly contributes to successful treatment of hypertrophic scars and incipient scar contractures. Laser therapy accelerates scar maturation and remodelling, reduces scar height, leads to scars fading and softening more rapidly and diminishes pruritus.¹⁵ In our experience, early and effectively applied laser therapy for incipient scar contractures was associated with significantly reduced need for reconstructive surgery. Since areas transplanted with the Meek technique did not form severe scar contractures requiring surgical treatment, we speculate that the Meek technique may possibly represent a lower risk than the mesh method (Figure 3). Mesh grafts are subject to subsequent contraction, which is greatest in the cleavage axis line of the donor site. Thus, this axis has the greatest risk of scar contractures. Based on our observations, this risk is smaller when using micrografts because individual graft islands are completely isolated and uniformly distributed in precise square patterns without mutual connections. This advantage is particularly highlighted in bending locations where the risk of scar contractures is the greatest. All 3 patients who underwent long-term follow-up and monitoring are presently fully self-sufficient and none have serious scar contractures. Superficial scars are in the hypertrophy regression phase.

CONCLUSION

We have used the Meek micrografting technique at our facility since 2013. In the Czech Republic, it is considered to be a newly introduced method that necessitates acquiring personal experience to ensure optimal performance of the procedure. Despite the small number of patients who have undergone this procedure yet, our experience has been positive and the effectiveness of the procedure has been clearly demonstrated. In the context of overall treatment management, we consider the Meek technique to be fully indicated and unambiguously beneficial for the surgical treatment of deep second- and third-degree burns in extensive thermal injuries associated with insufficient autograft donor sites.

Corresponding author:

Hana Klosová MD, PhD.

Burn Centre, University Hospital Ostrava

17. listopadu 1790

708 52 Ostrava-Poruba,

Czech Republic

E-mail: klosova.h@seznam.cz