A novel skin grafting modality: prefabricated large sheet of postage-stamp autografts and allografts to repair extensive burn wounds; a prospective matched-control study

Abstract

Background:

The excessively long operative time has been the greatest barrier to the success of transplanting postage-stamp auto- and allografts directly and piece-by-piece onto extensive burn wounds. To solve this challenge, the authors present a novel grafting modality, that is, the prefabricated-large-sheet grafting that moves the labor-intensive and time-consuming process of grafts-positioning before grafting and thereby markedly shortens the operative time.

Methods:

Twenty-one operations using the novel modality were performed on 11 patients with extensive deep burns. The grafting time using the novel modality was recorded and compared with that of the conventional piece-by-piece grafting. Eventually, the take rates of the two modalities were compared.

Results:

All patients were healed and discharged. The average grafting time per unit area (100 cm²) of prefabricated-large-sheet grafting and piece-by-piece grafting were (0.41±0.09) min and (7.46±1.07) min, respectively, and the difference is statistically significant(P<0.001). The average take rate of the prefabricated sheets was (85.43±6.14)% and that of the piece-by-piece transplanted grafts was (87.29±5.23)% and there is no significant difference(P>0.05).

Conclusions:

The prefabricated-large-sheet grafting significantly reduces the intraoperative grafting time while ensures uniformity of the skin grafts and secures good outcomes, thereby making the intermingled transplantation of postage-stamp auto- and allografts, which has been an excellent modality per se but limited to repair small residual wounds, now feasible to repair extensive deep burn wounds. It is worth wider understanding and application in the treatment of extensive deep burns.

Introduction

Highlights

• Reduce the operation time of intermingled transplantation of auto- and allografts.

• Moving the labor-intensive process of graft-positioning before operation.

• The new modality is now feasible to repair extensive deep burn wounds.

How to achieve wound coverage with severely insufficient autografts has long been a challenge to the treatment of extensive deep burns¹. In 1954, Jackson D. successfully healed a burn patient with alternately grafted strips of autologous and allogeneic skin, marking the introduction of intermingled transplantation of autografts and allografts into burn care². Jackson’s method requires a large supply of autografts and usually cannot achieve full coverage for extensive burn wounds in a single operation. In 1961, a modified technique based on Jackson’s was provided by Chih-Chun Y., Tsi-Siang S et al. It replaced the autograft strips in Jackson’s method with alternatively laid autologous and allogeneic skin squares (1 cm×1 cm) while keeping the allograft strips the same as previous³. The modified technique improved the efficiency of autograft usage^4,5.

Clinically, a much weaker allograft rejection has been observed in the bricklaying pattern compared with that in strips. To be specific, the epidermis of the allografts would gradually exfoliate and allow the autograft epidermis to creep over the allograft dermis, achieving a full coverage of the wound that is essential to stabilize the patient^6,7. Based on this, Shizhao J et al.⁸ replaced all the allograft strips in Shih’s method with alternatively laid auto- and allografts in a bricklaying pattern and produced a better outcome. The greatest merit of this method is that allografts fill up the gaps between autografts and become vascularized to achieve an effective coverage almost without any wound exposure, preventing wound desiccation, excess exudation, and energy consumption, as well as infections. However, both Xia and Shih’s methods require a labor-intensive and time-consuming piece-by-piece grafting, making them inapplicable to extensive burn wounds for the patients would be kept under general anesthesia for several hours until the procedure is finished.

This problem can be well solved by the novel modality in this study. The modality emphasizes the prefabrication of large sheets of evenly-laid postage-stamp auto- and allografts in a bricklaying pattern with a biological adhesive and a single-layer absorbent gauze before the accomplishment of wound preparation, that is, excision, debridement, and hemostasis. It significantly shortens the intraoperative grafting time, for the labor-intensive and time-consuming grafts-positioning procedure is accomplished in vitro on a sterile stainless-steel plate before grafting. The anesthetized patient would only need another several minutes, instead of several hours that are required in the conventional piece-by-piece in vivo grafting, to receive all the grafts. The grafts are uniformly distributed in the large sheet and positioned strictly according to the corresponding optimal layout that ensures the minimization of the largest distances between all autografts, thereby facilitating the growth and fusion for the new coverage. In addition, the sterile stainless-steel plate provides a flat surface where the small grafts can be evenly-laid and a cleaner background (compared with the bloody wound bed) against which the epidermal side can be better distinguished to avoid a flipped positioning. For these advantages, this modality is well worth sharing with the wider community of our burn professionals.

Methods

Introduction to the novel modality

Preoperative evaluation of available donor sites and graft sites and calculation of the autograft to allograft ratio

The area of the patient’s available donor sites (D, cm²) and graft sites (G, cm²) are carefully measured before operation. The autograft to allograft ratio would be 1:R in which the R is calculated by the formula R=(G/D−1) and rounded to the nearest integer. The optimal layouts for different R are presented below (Fig. 1).

Figure 1.

Optimal layouts of the postage-stamp auto- and allografts for different R. A.1:1; B. 1:2; C. 1:3; D. 1:4. Black squares represent autografts and white ones represent allografts.

Prefabrication of the large graft sheets

Adequate cryopreserved viable allogeneic skin (0.3 mm in thickness) is taken and rinsed thoroughly with saline for three times about 2 h before operation. The rinsed skin is cut into 0.7 cm×0.7 cm postage-stamp grafts using a quick cutting machine (Kexing Bio) and following the optimal layout for the corresponding R placed on the back surface of a sterile stainless-steel plate with the epidermis upwards (Fig. 2A). The process must be completed before operation. Upon its completion the patient is anesthetized and spilt-thickness autologous skin graft (0.3 mm) is harvested from available donor sites with an electric dermatome. The obtained autologous skin is also rinsed with saline for three times to remove all blood and hair residues and then cut into 0.7 cm×0.7 cm postage-stamp autografts that will be fitted into the reserved sites on the plate (Fig. 2B). All postage-stamp grafts are spaced 0.1–0.2 mm apart.

Figure 2.

Positioning postage-stamp allografts (A). Positioning postage-stamp autografts (B).

Upon the completion of positioning all auto- and allografts, the plate is tilted slightly to facilitate drainage of the residual saline till the epidermal surface is dried. Then a proper amount of MEEK Adhesive (Humeca) is sprayed from about 25 cm away and 5 min later an even tacky layer will be formed on which a single-layer absorbent gauze (Haomei) is carefully pressed to ensure a tight adherence. After another 5 min, a corner of the gauze is lifted up and then in a short-edge flip manner the large graft sheet entirely removed from the plate (Fig. 3). The excess gauze on the margin is trimmed off and the sheet placed in a saline-containing plate with the dermis upwards. The prefabrication of the large graft sheet is accomplished by the end of wound preparation, that is, excision, debridement, and hemostasis.

Figure 3.

The epidermal surface is evenly sprayed with the MEEK Adhesive (A). A single-layer absorbent gauze is gently and evenly pressed on the surface (B). The large graft sheet is removed from the plate in a short-edge flip manner (C).

Transplantation of the large graft sheet and subsequent care

The prefabricated-large-sheet is carefully applied to the wound. Care is exercised not to overstretch the sheet as it might undermine the take rate. A single-layer of fine mesh gauze dressing impregnated with silver sulfadiazine is used to wrap the grafted site. After that, multiple layers of coarse mesh gauze dressings are used to further compress and wrap. The dressings are removed for routine inspection 3 days postgrafting. If no unfavorable conditions such as excess exudation or infection occur, the single-layer absorbent gauze of the prefabricated-large-sheet can be kept for 2–3 weeks. Fine mesh gauze dressing impregnated with silver sulfadiazine and multiple layers of coarse mesh gauze dressings to compress and wrap are repeated as previous. Subsequently, the dressings are changed every other day. During dressing change, patches or spots of excess exudation necessitate the removal of the prefabricated-large-sheet’s single-layer absorbent gauze and appropriate antibiotic application or administration. A single grafting often cannot obtain a full coverage due to the shedding of some skin graft pieces. Small-size wound exposure only requires conservative treatment and large-size exposure needs additional grafting of small autologous skin pieces. No immunosuppressant or other antirejection medication is used during the course of treatment.

Indications

The proposed technique is suitable for large-size excised wounds.

For example, in our experience, when the entire upper or lower extremity, or the entire posterior trunk requires grafting, the conventional method, that is, intermingled transplantation of postage-stamp autografts and allografts, is not suitable and rarely used because it takes several hours to complete the piece-by-piece positioning procedure on the large-size excised wound. For these cases, the proposed technique is suitable for it only takes several minutes to finish the coverage of the large-size excised wound.

Clinical application

Inclusion and exclusion criteria and ethics approval

From January 2020 to August 2022, 11 patients with extensive deep burns treated in our center were enrolled in this study. Inclusion criteria: patients who met the diagnostic criteria for extensive deep burns; burn area: greater than or equal to 50% total body surface area (TBSA); burn depth: Ⅱ–Ⅳ degree; aged 18–59; consented to participate in the study. Exclusion criteria: patients with blood diseases, organ dysfunction, diseases of the immune system, malignant tumors, diabetes and mental illness before burns; not suitable for surgery; unable to cooperate. The flow diagram was shown in Figure 4.

Figure 4.

The flow diagram of the trail.

This study was approved by the ethics committee of our hospital (approval number: 2021KY026-HS001) and was registered at the China Clinical Trial Center. This work has been reported in line with the strengthening the reporting of cohort, cross-sectional, and case–control studies in surgery (STROCSS) criteria⁹.

Efficacy and take rate evaluation

Each patient received at least one grafting operation using prefabricated-large-graft sheets. The total size and grafting time were recorded and the grafting time per unit area (10 cm×10 cm) calculated. During the same procedure of each operation, a 10 cm×10 cm wound was randomly selected to receive auto- and allografts of the same size piece-by-piece following the same layout of the prefabricated-large-sheet and the time required to complete this process was recorded. On the 10th day postgrafting, the take rates of the two modalities were calculated.

Skin quality assessment of the resurfaced wounds

The patients were followed up for 1–2 years. Scar formation and function were assessed by a burn therapist with the Vancouver Scar Scale (VSS). In VSS, pigmentation (0–2), pliability (0–5), scar height (0–3), and vascularity (0–5) are rated, the total score ranges from 0 to 15. The higher the score, the severer the scar.

Statistical analysis

All data were statistically analyzed using SPSS 23.0 and expressed as mean±SD. A t-test was performed for comparison of the two groups for measurement data. P<0.05 was considered statistically significant.

Results

Graft data and take rate

The enrolled patients included 9 males and 2 females, with an average age of (52.90±19.70) years and an average burn size of (86.27±8.82) % TBSA. A total of 16 operations using the novel modality were performed. In this series, the prefabricated large sheets amounted to 39285 cm² and their grafted size ranged 10–25% TBSA. The average size of the prefabricated large sheets per operation were (2455.3±856.2) cm². The details are presented in Table 1 and Table 2.

Table 1.

General data of prefabricated-large-sheet grafting with different auto- to allografts ratio.

	Auto- to allografts ratio (1:R)
	1:2	1:3	1:4
Number of operations	5	10	1
Total size prefabricated (cm2)	14557	22428	2300
Average grafting time per operation (min)	12.0±6.1	10.4±5.0	8.0

Table 2.

Profile of the prefabricated-large-sheet grafting series.

			Size of the large sheet
No.	Grafted sites	auto- to allografts ratio	Absolute size (cm2)	Relative size (%TBSA)
1	Left upper and right lower extremities	1:2	4300	25
2	Back, buttocks, the back of both thighs, left upper extremity	1:3	3993	23
3	Left upper and left lower extremities	1:2	3500	21
4	Left upper and right lower extremities	1:2	3100	18
5	Left upper and right lower extremities	1:3	2600	15
6	Posterior trunk	1:3	2570	13
7	Both shoulders, left chest wall and the lower abdomen	1:3	2548	15
8	Left lower extremity	1:4	2300	15
9	Right lower and left upper extremities	1:3	2091	12
10	Left upper extremity and the back	1:2	2000	12
11	Back	1:3	1800	11
12	Right lower extremity	1:3	1753	10
13	Left lower and right upper extremities	1:3	1717	10
14	Left lower extremity	1:3	1696	10
15	The trunk	1:3	1660	10
16	The lower abdomen and the roots of both thighs	1:2	1657	10
Average			2455.3±856.2	14.4±5.0

The average grafting time of the prefabricated-large-sheet grafting and the piece-by-piece grafting per unit area was (0.41±0.09) min and (7.46±1.07) min, respectively (Table 3). The novel modality significantly shortens the grafting time (P<0.001).The average take rate of the prefabricated large sheets was (85.43±6.14) % and that of the piece-by-piece transplanted grafts was (87.29±5.23)% and there was no statistically significant difference (P>0.05).

Table 3.

Grafting time per unit area and the take rate for the two methods.

	Prefabricated-large-sheet grafting	Piece-by-piece grafting	P
Grafting time per unit area(min/100 cm2)	0.4±0.1	8.0±1.0	0.000
Take rate (%)	85.6±6.4	87.2±5.5	0.1

Skin quality assessment of the resurfaced wounds

Follow-up observation in the 11 patients for 1–2 years after routine antiscar treatment using elastic sleeves showed that scar formation was mild and the surface of the grafted areas were smooth and flat with pliable skin (Fig. 5J-L). The VSS mean values of pigmentation, pliability, scar height, and vascularity were 1.67±0.48, 0.48±0.33, and 0.76±0.62, 0.10±0.30, respectively. The total score was 2.86±1.19. No significant contracture or dysfunction were observed in areas overlying knees, elbows, and other large joints in the 11 patients.

Figure 5.

A–E: the prefabrication of the large graft sheet. F: the left lower extremity received excision. G: the prefabricated-large-graft sheet was applied to the excised wound. H: On the 17th day postgrafting, the single-layer absorbent gauze on the prefabricated-large-sheet was removed. I: On the 30th day postgrafting, the grafted areas completely healed. J–L: Follow-up 11 months postgrafting, skin of the resurfaced wounds was soft and elastic and the knee’s flexion and extension activities were in good performance.

Typical case

The patient was a 44-year-old female. She sustained multiple flame burns over the body due to a gas cylinder explosion, and 6 h later was admitted to our center and diagnosed with a burn size of 85%TBSA (53% TBSA was third-degree) and inhalation injuries. The wound of left lower extremity received prefabricated-large-sheet grafting. Preoperative assessment indicated the area of available autologous donor sites was 460 cm² and the area of graft sites was 2,400 cm². A large graft sheet of 2300 cm² was prefabricated with the postage-stamp auto- and allografts positioned following the optimal layout for R=4. The positioning took 70 min. Two surgeons performed the piece-by-piece grafting on the selected 100 cm² wound in 9 min and the large sheet grafting for 2300 cm² in this operation only took 8 min.

Postoperation, fine mesh gauze dressing impregnated with silver sulfadiazine and multiple layers of coarse mesh gauze dressings were changed every other day. The single-layer absorbent gauze of the prefabricated-large-sheet was removed on the 17th day postgrafting and the take rate was almost 100%. The allografts’ epidermis all exfoliated 30 days postgrafting and the epidermis of autografts crept over the allografts’ dermis and fused to achieve wound closure. The patient was discharged on the 48th day postburn upon recovery.

A follow-up visit 11 months later showed that: the surface of the prefabricated-large-sheet grafted sites was smooth and flat with soft and elastic skin; no apparent hypertrophic scar formation or contracture was observed; the knee joint activities such as flexion and extension were normal (shown in (Fig. 5).

Discussion

The priorities for treating extensive deep burns are to achieve timely removal of necrotic tissue as well as effective coverage of the wound, thus preventing a series of severe complications such as extensive wound exposure, necrotic tissue lysis or infection and thereby reducing the patients’ mortality¹⁰. As of today, autografting is still the best choice for permanent coverage of deep wounds¹¹.

To improve the usage efficiency of the autografts and the outcome, burn surgeons have explored the deployment of allografts in supporting autografting. Various methods of intermingled transplantation of auto- and allografts have been developed, including the Jackson method, the conventional piecemeal grafting of auto- and allograft, and the technique of embedding small autografts in the openings of large allograft sheets, etc.

The intermingled transplantation of auto- and allografts can effectively increase the expansion rate of autografts without compromising the coverage result and the grafts’ viability. Unlike xenografts, the allografts filling the gaps between autografts, would become vascularized to achieve an effective coverage with a minimum wound exposure, protecting the wound from desiccation, excess exudation, and infections. The narrow spaces between the grafts can facilitate the drainage of exudation and thus enhance the take of grafts and the healing result. Studies have shown that 7 days after intermingled transplantation of auto- and allografts in a bricklaying manner, the allografts would have a rejection response with varying degrees of epidermal cell necrosis, and the epithelial cells at the edge of the autografts would begin to proliferate and creep outwards, gradually extending into the space between the epidermal and the dermal layers of the allografts, forming a so-called ʻsandwichʼ where the dermal layer of the allografts were sandwiched between the creeping epidermal layer of the autografts and the underlying connective tissue³. Animal studies have shown that 28 days after intermingled transplantation of auto- and allografts in a bricklaying manner, exfoliation of the allografts’ epidermis and fusion of the autografts’ epidermis can be observed and a complete wound coverage can be obtained⁶. Researchers have found that it would be better to reduce as much as possible the size of each graft (but still should be greater than 0.09 cm²) and the spacing between the grafts (no more than 1 cm) for this would allow the autografts’ epidermis to proliferate and creep at a rate that catches up with the allografts’ epidermal rejection and exfoliation to avoid exposure of the wound¹². Xia Zhaofan et al. reported the good performance of intermingled transplantation of postage-stamp auto- and allografts in repairing wounds and their follow-ups in the subsequent 1–2 years showed that the surface of the grafted area was smooth and flat with serviceable skin elasticity and mild scar formation⁸.

Presently, the grafts-positioning process in conventional intermingled transplantation has not been automated yet and still requires manual and piecemeal positioning of small grafts onto the wound surface. It usually lacks uniformity and its laborious process prolongs the operative time, which highly increases the associated risks. For instance, in our experience, an adult patient with a full dorsal burn would need ~4 h to have all the postage-stamp auto- and allografts positioned onto the wound surface piece-by-piece if the procedure is performed by four surgeons simultaneously, resulting in a prolonged anesthesia and wound exposure. Prolonged wound exposure in a lengthy operation would lead to the desiccation of viable tissue, thus extending the depth of injury and increasing the risk of infection, which is particularly detrimental to patients with extensive deep burns. In addition, the prolonged in vitro placement of autografts would also lead to their reduced vitality. It is therefore crucial to build a consensus on how to effectively minimize the operative time for the intermingled transplantation.

The modality described in this study introduces the prefabrication of a large sheet of postage-stamp auto- and allografts with evenly sprayed adhesive and a single-layer absorbent gauze before it is applied to the wound, which can significantly boost efficiency and can be effortlessly repeated. It was first tested on small wounds about 1600 cm², and after its good and stable performance was validated in increasing cases, it was further applied to much larger wounds. The largest size in this series covered by the prefabricated sheets reached 4300 cm². To ensure a good surgical outcome, the donor sites and the graft sites must be carefully measured preoperatively, and the shapes and sizes of the large graft sheets must be appropriately cropped to fit the graft sites well, so as to obviate the need for extra cutting or piecing during the grafting procedure.

The layouts of the auto- and allografts for different R can be rather varied. The study just presents the optimal layouts for several Rs, and all of them are based on previous studies and have been validated by our team to ensures the minimization of the largest distances between the autografts to facilitate the best growth and fusion¹³. Once the R and the corresponding layout is determined, surgeons can simply follow the selected pattern and position the grafts on the back of a stainless-steel plate, hence a streamlined procedure that both saves time and ensures uniformity. Again, take an adult patient with full dorsal burn for example, the grafting time using prefabricated-large-graft sheets was only about 10 min, markedly less than the time required in piece-by-piece grafting (4 h with four surgeons in our experience). The large sheet grafting takes less than one tenth of the time needed in piece-by-piece grafting therefore significantly boosting the grafting efficiency.

The adhesive in this study is a highly sticky and safe bio-glue that has been widely used in the MeeK grafting technique¹⁴. It is advised to be sprayed at a distance of 25 cm from the skin surface since too short a distance would lead to the shifting of the grafts and too long a distance would reduce spray efficiency. A proper amount of spray is also advised for it would form a tacky layer to which all grafts tightly adhere and avoid excessive glue filling up the holes in the gauze and resultant poor drainage. The authors also noted that for unknown reasons, not all autograft epidermis could achieve fusion before the allograft epidermis exfoliated. These cases require additional autografting to cover the wound.

The study puts its emphasis on prefabrication and did not include the comparison of the healing outcomes across different sizes of grafts. Theoretically, a higher auto- to allograft ratio would see a better healing result. This study observed satisfactory results with the auto- to allograft ratio of 1:4 but further randomized controlled trials can be anticipated to explore the performance of smaller ratios.

It is also noted that cultured epithelial autografts (CEA) have been widely used in the treatment of extensive burn wounds. Akita et al.¹⁵ reported that CEA plus 1:6 mesh grafting could obtain equal or similar results to conventional 1:3 meshes. What the CEA method and our method have in common is that both methods facilitate expansion of the limited autografts and achieve a full coverage with a physiological dressing, effectively protecting the wound from exposure. However, the difference is that the CEA method would require 3 to 4 weeks to get the cultures ready for clinical application whereas our method uses allografts to fill up the gaps between the autografts and this saves time since allografts are readily available. In view of this, our method is particularly suitable for the early treatment of extensive deep wounds.

Conclusion

To conclude, the novel modality in this study emphasizes that the place for positioning grafts be relocated from the graft sites in vivo to the sterilized stainless-steel plate and the conventional piece-by-piece positioning after wound preparation be reformed to the prefabrication of graft sheet simultaneous with wound preparation. It makes the intermingled transplantation of small auto- and allografts, which has been an excellent modality per se but limited to repair small residual wounds, now feasible to repair extensive deep burns. The modality requires only a noticeably short grafting time and ensures uniformity of the grafts as well as good outcomes. It can serve as a powerful instrument in the toolbox for the treatment of extensive deep burns.

Ethical approval

This study was approved by the ethics committee of Chinese PLA General Hospital (approval number: 2021KY026-HS001).

Consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Sources of funding

This work is supported by the Program of National Natural Science Foundation of China (82072169, 82272279).

Author contribution

C.A.S.: created the novel skin grafting modality; B.H.Z. and X.Z.L.: collected and analyzed the clinical data; J.H.C., T.J.S., D.J.L., and H.P.D.: participated in the surgery; C.A.S., B.H.Z., X.Z.L., and H.G.Y.: wrote the manuscript.

Conflicts of interest disclosures

The authors declare that they have no financial conflicts of interest with regard to the content of this report.

Research registration unique identifying number (UIN)

This study was registered at the China Clinical Trial Center (registration number: ChiCTR2200059432).

Guarantor

Chuanan Shen.

Data availability statement

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Provenance and peer review

Not invited.