Acellular Dermal Matrix-Assisted Tissue Expansion for Giant Congenital Melanocytic Nevi of the Extremities and Trunk in Pediatric Patients

Abstract

Background: Tissue expansion for treating giant congenital melanocytic nevi (GCMN) is a commonly used surgical method. However, the procedure's efficacy is often hindered by anatomical and histologic characteristics and blood supply, particularly in the extremities and trunk. Enhancing expansion efficiency while reducing complications is thus a topic to be investigated, especially for pediatric patients undergoing rapid physical and psychological development with higher risks of noncompliance to medical instructions. The purpose of this study was to explore the effectiveness of expansion in extremities and trunk by immobilizing the acellular dermal matrix (ADM) in the gravitational force zone of inflating expanders.

Methods: All patients involved in this research underwent ADM-assisted tissue expansion in either the extremities or trunk. ADM was fully flattened, securely fixed to the lower pole of the expander, and subsequently attached to the inner surface of the expanding flap.

Results: From 2021 to 2023, a total of 9 pediatric patients with GCMN underwent ADM-assisted tissue expansion. All patients achieved the desired expansion volume without experiencing petechiae, ecchymosis, or skin ulceration in the ADM-covered area. The process was well tolerated by all patients, with no reports of itching, pain, allergic reaction, or fever. During the flap transfer, the ADM was observed to be firmly adhered to the expanding flap with discernible capillary network.

Conclusions: ADM-assisted tissue expansion demonstrates promise in augmenting expansion efficiency and reducing the time needed for surgical intervention in the extremities and trunk, thereby presenting significant clinical value for pediatric patients with GCMN.

Clinical question/level of evidence: Therapeutic, IV.

Fig. 1.

The local expanded skin under the lower pole of the expander ulcerated, exposing the expander without infection during the expansion process.

Fig. 2.

The procedure of ADM fixation on the internal side of the expanded flap. (Left) The sutures held the 4 corners of the ADM. (Center) The ADM was suspended by the sutures and placed below the flap after being flattened. The sutures passed through the above skin and anchored the ADM on the internal side of the flap. (Right) Oil gauze was used for further fixation.

Fig. 3.

Intraoperative image after tissue expander removal. (Left) ADM adhered to expanded flap. (Right) Local magnification to exhibit capillary network.

Fig. 4.

Clinical case. (Above, left) A 4-year-old female patient with giant congenital melanocytic nevus involving the right scapular area and right upper arm. (Above, center and right) The ADM was immobilized on the inner side of the expanding flap. A 350-mL kidney-shaped expander was implanted in the back. Both black dotted boxes and asterisks mark the location of ADM. (Below, left) In the late stage of expansion, ecchymosis (black dotted ellipse) was observed on the lateral wall of the expanded flap. The condition was reversed by reducing the frequency of water injection (from twice a week to once a week), resulting in expansion continuance. The expansion reached the expectation at 6 months postoperatively; the position of the ADM is marked by an asterisk. (Below, center) Immediate image after ADM removal. (Below, right) Immediate image after expanded flap lifting.

Fig. 5.

HE staining of the expanded flap. (Left) ADM-covered areas involved skin, capsule, and ADM in turn. (Right) Local magnification (the lumen structure is marked by the arrows).

Fig. 6.

α-Smooth muscle actin–positive myofibroblasts in the capsule. (Left) Myofibroblast distribution in the ADM group and control group (target cells were stained brown). (Right) Statistical analysis of average optimal density between the ADM group and the control group (n = 3 for each group). ***P < 0.001.

Fig. 7.

Thickness of ADM and capsule. (Above, left) The thickness of ADM integrated into the expanding flap was thinner than in the control group (commercialized product). (Above, right, and below) The capsule thickness, epidermis thickness, and dermal thickness between control group (non–ADM-covered region) and ADM group (ADM-covered region) (n = 3 for each group). **P < 0.01; ****P < 0.0001; ns, not significant.

Fig. 8.

Schematic diagram of ADM-assisted tissue expansion. (Left) The ADM was fixed interior to the expanded flap, enveloping the lower pole of the expander. (Right) When a patient assumes an upright position, the mechanical force produced by the weight of the expander is evenly distributed toward the surrounding skin.