1. Principles of surgical treatment: Except for some superficial scars which generally do not need to be treated, all other types of scar tissues need to be treated due to different degrees of contracture deformity and dysfunction. In addition to deformity and dysfunction, scarring on the face and neck can also cause mental and psychological burden to the patient due to its impact on appearance. The scar on the hand mainly causes functional disorders. Scar contracture on the back of the hand can lead to dorsiflexion of the metacarpophalangeal joint and inversion of the thumb over time, resulting in the so-called “claw-shaped hand”, which can cause almost complete loss of hand function. Scar contracture in other parts of the body can also affect the normal movement of individual limbs or joints. All types of scar contractures with functional impairment need to be treated. In terms of current technology, this treatment is limited to surgical excision of the scar and the application of various reconstructive surgical methods (including implants) to repair the wound and correct the deformity. Some keloid scars that do not produce contracture symptoms but cause persistent itching, painful symptoms, or frequently break down should also be considered for excision and repair. Deep scar tissue can also sometimes produce neurologic symptoms by contracting and pulling on the surrounding organs. This symptom is not easily diagnosed, but if diagnosed, the results of surgical treatment are more satisfactory. For smaller hyperplastic scars that affect functional activities or form deformities, especially on the face and hands, surgical excision should be considered and skin implants should be placed. However, such excision should not be performed during the early congested stage of the scar, otherwise it may cause more hyperplasia of scar tissue (especially in the marginal part of the implant area). It is usually better to wait for the degenerative stage before excision and skin grafting. For the treatment of atrophic scar, in principle, excision should be performed as early as possible to release the contracture and reset the normal tissue, and then medium-thickness skin grafting should be performed on the wound surface. If the area is too large for total excision, partial excision and skin grafting can be performed on the most severe part of the contracture to promote the remaining contraction and gradually enter a stable state. In areas where ulcers are frequently present, it is usually not necessary to wait for the wound to heal, but to perform excision early. In addition to the use of free skin grafts, the application of a tipped flap graft should be considered in cases where an atrophic scar immediately adjacent to the skeletal surface is encountered, or where the basal blood supply is extremely poor, to prevent re-rupture. The tipped flap graft includes local flap transfer, distal skin tube graft, and contralateral limb cross flap graft. In severe trauma with deep tissue defects such as subcutaneous tissue, muscle or bone, a depressed scar below the normal skin surface will be formed after the wound heals. When the depression is light, it only causes sulcus or saucer-like tissue depression on the body surface, which hinders the beauty; in serious cases, it may directly adhere to tendons, muscles or skeletal tissues, or to nerve trunks and other tissues, sometimes causing serious dysfunction, or breaking down after a long time, or producing pain and other symptoms. 2.Several points of attention before surgical treatment: The treatment of scar, especially for extensive scar left after severe burns, must pay attention to the following points before considering taking surgical treatment. (1) Generally proliferative scars should not be treated surgically prematurely, as described above. However, when there is contracture scarring across the face, severe lid ectropion or micrognathia is often present. In such cases, localized lid ectropion correction or microstomia should be performed early to prevent serious consequences of prolonged corneal exposure or to facilitate feeding. For the rest of the face, the scar should be treated surgically after the proliferative phase has subsided. In addition, for scar contracture of the hand, the author advocates earlier surgical treatment. Surgery can be performed when the wound has healed for 2-3 months, when there is no residual local infection, and when the patient’s general condition permits. This prevents serious secondary deformities of the joints and tendons in the hand. (2) Contracture often begins to occur early in the scar formation of the healing wound. At this point, you can consider cutting at the most obvious part of the contracture; or removing only part of the scar. A skin graft will be placed to reduce the contracture. Later, the rest of the area will be treated as appropriate. Sometimes, after the above treatment, the remaining part of the scar may gradually become a stable state, and no further treatment can be done later. (3) Before surgery, appropriate physical therapy and sports therapy, such as ultrasound and wax therapy, can be given to soften the scar. After applying physiotherapy and physical therapy, the extent of scar excision can often be reduced. Other options such as pressure bandaging and herbal treatment can also be used. (4) The scope of scar excision should be limited to the area that affects the function most seriously, especially for patients with extensive scar contracture and insufficient skin source. If too much of the scar area is removed or all of the scar area is attempted to be removed, problems such as insufficient skin supply area often occur. Surgical treatment: Surgical treatment of keloid scars requires different methods according to the characteristics of the scar. (1) Treatment of superficial scars: Most superficial scars do not require treatment, as described above. However, if it occurs on the face and hinders the integrity of the appearance, surgical excision can be carefully considered. If the area is small, it can be excised and directly sutured in one surgery; for larger area, staged excision and direct suturing can be applied. No matter once or repeatedly, the incision and sutures should be designed in the direction of the dermatoglyphic line; in case of right-angle intersection with the dermatoglyphic line, a “Z” shaped incision should be designed to rectify it, otherwise it will affect the final result and even lead to another deformity. The treatment of large superficial scar is more difficult, and the result of excision with free skin implant is hardly satisfactory in terms of color, and sometimes the contraction of the skin implant may have adverse consequences. (2) Treatment of depressed scar: When scar tissue causes depressed deformity on the body surface, there is often a loss of subcutaneous tissue, muscle or bone tissue. A simple depressed scar is only a linear scar and its local area of depression; an extensive depression is more extensive and deeper. To correct this deformity, it is necessary not only to treat the scar on the skin, but also to fill the defect with different methods according to the severity of the depression in order to restore the normal shape. For simple linear depressed scars, a very thin layer of epithelial tissue on the surface of the scar can be removed first, leaving the deep scar tissue behind; then a transverse incision is made under each side of the skin to subconsciously separate the subcutaneous tissues on both sides, pull together the wound edges, and suture over the deep scar tissue. Generally, the scar that is not deeply depressed can be rectified after applying this method. If the depression is deeper, this method will not be effective. One or two tipped fatty tissue flaps can be designed in the subcutaneous tissue near the incision, rotated and filled underneath the suture line. However, care should be taken not to cause another sunken deformity in the immediate vicinity. When dealing with an extensive depressed scar, in addition to excision of the scar tissue, it is necessary to graft or fill the depression with some kind of tissue in order to improve the appearance. In addition to considering the filled graft tissue, attention should be paid to the tension of the tissue covering the skin after scar excision. Overlying the grafted tissue, if the blood supply to the overlying skin is poor, there is a risk of graft failure. Local transfer of the flap is a better method in this case, but care should be taken to avoid creating another deformity. A distant flap or duct graft should be considered only if there is a significant lack of adjacent skin tissue sources. The tissue to be filled can be as needed, such as dermis, fascia, fat, cartilage, or bone. Sometimes a composite tissue such as dermal fat or fascial fat can also be used. For large sunken deformities, a dermal canal can be designed to fill the subcutaneous defect with a tipped adipose tissue graft, which often results in a larger free fat graft. Cartilage or bone grafts can be applied for depressions that are generally caused by skeletal defects. Non-biological substances such as hydroxyapatite and silicone rubber can be applied. (3) Treatment of linear scar: Linear scar is often seen after trauma or surgical incision suture. Clinically, it is common to see some incisional scars after suturing, which not only have a wide proliferative scar in the middle, but also have a row of significant and prominent dotted scar on each side. This scar sometimes leaves only a shape defect, but sometimes it also causes contracture due to linear scarring. Itching and pain are also present during the hyperplastic phase of the scar. The treatment is to remove the linear scar and then apply the “Z” principle to form one or several triangles, which relieves the contracture and also prevents new contracture scar after the wound heals. If there is a prominent dotted scar on both sides of the scar, multiple W-shaped surgery can be performed to repair the scar. (4) Treatment of webbed scar contracture: If the contracture of the cord-like scar on the flexor surface of the joint is prolonged, the skin and subcutaneous tissue on both sides of the contracted scar can gradually elongate and become webbed scar contracture. Large webbed scars are commonly found on the anterior side of the neck, axilla, elbow fossa, slapping fossa, anterior ankle and other areas; small webbed scars can be found on the inner and outer canthus, nasolabial folds, corners of the mouth, palmar surfaces of fingers, and finger webs. Some webbed scars also appear in a circular pattern at the openings of body orifices, such as the corners of the mouth, urethral orifice, external vaginal orifice, internal trachea, external nostril, and external artificial anal orifice, etc. The main symptom is the narrowing of the caliber, which affects normal function. Webbed scars can generally be released by applying the “Z” principle of surgery. The operation is simple and effective. The “Z” incision is designed to make full use of the staggered interchange of the stretched skin and subcutaneous fat tissue to make the webbing disappear and release the contracture at the same time. The postoperative suture line at the margin is not at right angles, thus preventing the recurrence of contracture. Generally speaking, after the two triangular flaps are interchanged, the trauma can be completely eliminated; however, in the case of heavy contracture, there is still a part of the trauma exposed after transposition, which can then be repaired by medium-thickness skin graft or local flap transfer. For the treatment of webbed scars in various areas, please refer to the relevant chapters. Circumferential scar contractures can also be managed by applying the “Z” principle, but usually more than one “Z” incision is required. Congenital circumferential contracture of the limb also belongs to this type of contracture, which can also be released by applying the “Z” principle. (5) Treatment of large scar contracture: The principle of treating large scar contracture is to remove part or all of the scar in the area, and after the contracture is released, that is, to perform skin grafting or flap transfer repair on the wound surface. In general, if the contracture is mild and the scar is not deep, free skin grafting is appropriate. However, if the contracture is severe and the scar is close to deep tissues such as muscles, tendons or bones, flaps are preferable. The flap can come from adjacent tissues, or can be taken from a distant duct or direct flap transfer. These must be planned beforehand, adequately prepared, and then operated on as planned. Prolonged spastic contractions of the scar, especially those caused in early childhood, can affect the development of the limb muscles, tendons, blood vessels and nerves, as well as bones and other tissues, causing shortening and deformity. In this case, it is often impossible to release all the contractures after removing the scar. In this case, it is important not to use violence to reset the contracture in order to avoid damaging these tissues, or thus stretching and thinning the caliber of the blood vessels, blocking the blood circulation or pulling the nerves and causing serious consequences. In this case, the limb should be placed in the most functional position for implantation, to be corrected with continuous traction and physical therapy after surgery. If necessary, tendon lengthening, joint capsule dissection, joint ligament excision and other auxiliary surgeries are feasible to achieve adequate release. (6) Treatment of deep scar contracture: Trauma deep inside the body, such as stab wounds or shrapnel wounds, may often form a large amount of scar tissue in deep tissues, which not only adheres to peripheral nerves and muscles, but also, as a result of contracture, can tract the surrounding tissues for reflex pain and muscle disorders. When dealing with this kind of scar, two points should be noted: ① The location, extent and depth of the scar are often difficult to estimate exactly before surgery, and sometimes they can only be determined during surgery. Sometimes, the scar may be attached to important organs, making it difficult to perform radical surgery, so adequate preparation is required before surgery. The cavity created after excision should be filled with tissue to eliminate it, otherwise a new scar contracture will be formed. This kind of filling tissue is better to use adipose tissue for transplantation; free fat block or adipose tissue with tip can achieve the treatment purpose, and the latter is better. (7) Proliferative scar: surgical treatment is only used when there is functional impairment or morphological change. The principle of surgery is to excise the scar, fully release it, correct the deformity, and cover the wound with a skin slice or flap. For cases with large scar area and lack of skin source, only the scar can be excised or partially excised, only to completely loosen the contracture and repair the defect with skin pieces; the residual hyperplastic scar can gradually soften on its own because the tension disappears. (8) Keloid scars: It is well known that surgical excision of keloid scars is extremely prone to recurrence, and the recurrence is often larger than in the past. Therefore, many scholars believe that surgical excision alone is not meaningful in the treatment of keloids and that a combination of other methods is needed to achieve better results. Hynes describes the elimination of the keloid until it is level with the surrounding skin, followed by a bladed thick skin graft. He notes, however, that the keloid must be mature and pale; otherwise, the fibrotic process will reoccur postoperatively. To prevent the formation of keloids in the donor area Ketchum recommends the use of a thick skin graft (0.02-0.025 cm) and that the donor area should be selected for postoperative pressure. Regardless of the surgical approach, it is important to minimize tissue damage, hematomas, necrotic tissue, dead spaces, infection, and tension after keloid excision. This is because increased tension can stimulate fibroblast proliferation.