This type of scar is below the normal skin surface. Smaller depressed scars are commonly seen after smallpox or chicken pox, or after acne. Punctate depressed keloid scars are generally small in extent, and the principle of treatment depends mainly on the degree of depression. If the scar is shallow, skin abrasion is feasible. If the scar is deeper, the scar can be excised and sutured directly, or the scar can be filled with epidermis in situ to flatten the depression. Surgical methods: (a) Excisional direct suture method Suitable for small punctate depressed keloid scars. The long axis of the scar is used as the longitudinal axis, and a shuttle-shaped incision is made along the normal skin of the depression edge, and the scar and subcutaneous tissue are excised in a wedge shape and sutured in layers. (2) Scar tissue filling method is suitable for wider and deeper depressed keloid scars. With the long axis of the scar as the longitudinal axis, a shuttle incision is made along the normal skin of the edge of the depression and the skin is incised to the subcutis. The epidermis of the scar is removed, leaving the deeper tissue in place for filling. The subcutaneous tissues on both sides of the incision edge are then fully peeled off and the incision is closed in layers. The purpose of depressed scar surgery is to restore the flatness of the skin surface, for this reason, the incision should be designed on the normal skin with the same thickness of subcutaneous tissues, moderate peeling and reduction of the subcutaneous tissues under the cut edge, and suturing in layers. Complications and prevention: The main complication is the postoperative incision is linear sunken concave unevenness or scar growth, which can be avoided by designing and operating according to the points of attention. If it occurs, it is advisable to trim the scar locally again after 3-6 months of surgery for scar stabilization. The key is that the incision must conform to the crease line and achieve tension-free suture. II. Strip scar revision Facial skin contusions and cuts, if the post-injury debridement and suturing are improper, excessive tension in the suture incision or thick stitches and large threads, post-operative infection, etc., obvious strip scar is often formed after healing. If the facial surgical incision is not accurately aligned with the tissue level and heals poorly, it may also form a striped scar, which will hinder the appearance and require revision surgery. The principle of surgical treatment for striated scar is to remove the scar tissue, apply basic techniques such as Z-forming or W-forming, and repair according to the principles of sterile, non-invasive or minimally invasive plastic surgery and tension-free suturing. Surgical methods: (a) Excisional direct suture method Suitable for short and narrow small striated keloid scars. Using the long axis of the scar as the longitudinal axis, a shuttle-shaped incision is made along the normal skin of the scar margin. Cut the skin to the subcutaneous tissue layer, excise the scar tissue completely, make subcutaneous peeling on both sides of the cut edge, and suture the incision in two layers: subcutaneous dermis and skin, especially the dermis must be well sutured. (B) Z-plasty For strip scar around the eyes, nose and mouth, which has pulling deformation on the tissues and organs such as eyes, nose and mouth. The Z-shaped incision is designed with the long axis of the strip scar as the longitudinal axis, and the length of the lateral arm should not exceed 1.5-2.0 cm. Depending on the deformation of the tissues and organs, the angle of the two triangular flaps may not be equal, and is generally controlled at 30-60 degrees. The scar tissue is excised according to the design, and the flap is lifted after cutting the skin and making subcutaneous peeling. The two flaps are transposed and sutured together. (C) W-plasty For long, wide and irregular scar interlacing with normal skin and rigid scar of sharp injury. Using the long axis of the scar as the longitudinal axis, a continuous W-shaped incision line is made on both sides of the scar, with each short arm of the line about 4-7 mm long and the angle between adjacent short arms 50-55 degrees. After marking the incision line, use a No. 11 sharp knife to make a serrated cut. When using the knife, the tip of the knife is inserted into the skin first, and the tip of the knife points to the outside of the scar before making the incision, so as to make a regular serrated incision. The scar tissue is excised and a moderate subcutaneous peel is made on both sides of the incision. After subcutaneous reduction sutures, the triangular flaps on both sides of the incision edge are interpositioned and accurately aligned. Points to note: (1) Z-plasty can release the scar contracture and flatten the local deformed tissues. Because of the long incision and large extension of Z-plasty, a single Z-plasty should be designed in the facial area according to the skin fold line, and a continuous Z-plasty is required if necessary. (2) When designing the W-shaped incision, the length and angle of the short arm should be adjusted appropriately according to the shape and nature of the scar. If the short arm is too long, too much normal skin will be excised; if the short arm is too short, the postoperative incision scar will be prone to contracture due to lack of elasticity; if the angle of the short arm is too large, the postoperative incision scar will tend to be linear and prone to contracture; if the angle of the short arm is too small, it is not conducive to the operation of incision suture and also affects the blood flow at the tip of the triangular flap. In addition, the Y-V shaping should be used in combination with the Y-V shaping as appropriate to reduce the amount of normal skin excision, avoid the “cat ear” deformity at the ends of the incision line, and make the incision line basically conform to the skin tension line after suturing. (3) W-plasty can be used individually, but the length of the single W-plasty incision is longer than that of the shuttle excision method and Z-plasty method, and more normal skin needs to be removed. For longer strip scars, two or more Ws are usually used in conjunction, and the postoperative scar is composed of multiple short scars, which has the advantages of changing the bowstring-like or depressed appearance of a straight scar, intertwining the normal skin with the serrated scar, and blurring the boundaries of the scar to make it less detectable. Complications and prevention: The main complications are poor survival of the Z-shaped or triangular flap due to poor blood supply, excessive tension after suturing the incision, infection, postoperative scar hyperplasia and linear scar contracture, which affect the appearance and function. Therefore, the design and surgical operation must follow the key points of attention in order to obtain the effect of reducing postoperative scarring.