Scars, congenital malformations and large body surface masses (nevus nigricans, sebaceous nevi, verrucous nevi, etc.) have a great negative impact on the physiology and psychology of preschool children and require urgent treatment. Skin defects after excision of larger lesions often cannot be directly sutured. The color and texture of the transplanted skin pieces are significantly different from the surrounding skin after using traditional skin grafting, which affects the cosmetic effect. Skin expansion can provide additional skin with texture, color, hair distribution and sensory function very similar to the repair area, and through local flap transfer, the tissue defect can be repaired without adding new donor scar. Moreover, the rapid growth and metabolism of children’s skin, strong regenerative ability and good extension properties are conducive to a good expansion effect. What is “soft tissue skin expansion”? Soft tissue dilation is a procedure in which a soft tissue expander is placed under the normal soft tissue of the skin and the volume of the expander is increased by injecting fluid (isotonic sterile saline) into the expansion capsule, which exerts pressure on the surface soft tissue of the skin, causing it to expand and create new “extra” soft tissue of the skin. A method of covering the wound and repairing the defect. (1) Stage 1 surgery: dilator insertion, selection of a suitable skin donor area near the lesion to be removed, subcutaneous separation of a dilator insertion gap, insertion of the dilator (Figure 1), suturing of the wound, pressure dressing, postoperative application of antimicrobial agents, and observation of the dilator insertion area for infection, hematoma, and other conditions. (2) dilator water injection: 1 week after surgery, the wound heals well, and dilator water injection can be started (Figure 2), and sterilized saline is injected via the injection jug attached to the dilator capsule embedded under the skin, usually 1-2 times a week, with each injection amount being about 10%-20% of the volume of the dilator capsule, and the total amount reaching 1.5 times-2 times the labeled volume of the dilator capsule (for example, a dilator labeled 100 ml can eventually (For example, a dilator labeled 100 ml can end up with 150 ml-200 ml of water.) . After the desired volume of dilatation has been reached, the second stage of surgery can be performed after a waiting period of about 1-2 weeks. (3) Stage 2 surgery: the dilator is removed by cutting along the original surgical incision or the side of the lesion near the dilating capsule, and the soft tissue lesion that needs to be removed is excised, and the newly obtained skin is dilated to cover the lesion defect according to the pre-designed flap (Figure 3-4, Figure 5-6) to achieve the effect of tissue repair. The silicone rubber used to manufacture the expander is a medical silicone rubber of extremely high purity, which has been widely used in the medical field, and its composition is similar to that of the silicone rubber prosthesis used for rhinoplasty and chin augmentation, which has been used in clinical applications for more than half a century. Due to the inertness of silicone rubber material, the tissue compatibility is very good, and the long-term and large number of clinical application results prove that it is safe to be placed into the human body (subcutaneous layer). Moreover, after a period of 1-2 months of expansion, the dilator needs to be removed by the time of the second-stage surgery, and there is no need for long-term retention in the body. The outstanding disadvantages of skin soft tissue dilatation are that the child must undergo 2 surgeries, and the process of water injection into the dilatation capsule requires attention to local skin cleaning and disinfection and protection from collisions, scratching, and mosquito bites. Although the treatment period of skin soft tissue expansion is relatively long, it is an effective treatment modality for patients because its treatment effect is better than traditional skin grafting and flap transfer methods in some patients, and the secondary deformity of the donor area is small, which overcomes the disadvantage of traditional tissue transplantation of “tearing down the east wall to make up for the west wall”.