Syndactyly deformity

　　Firstly, etiology

　　Syndactyly deformities belong to partial limb partial differentiation disorders. By the fourth week of fetal development, the distal end of the upper limb bud begins to show finger contours, and by the eighth week, the differentiation of the fingers is clear. At 7-8 weeks, the embryo may experience extremely minor injuries, causing partial stasis in the differentiation and development of the fingers, and掌板 differentiation disorders. Most cases are autosomal dominant inheritance.

　　Secondly,Pathology

　　The manifestations are divided into skin deficiency, skeletal deformities, and vascular and neurological deformities.

　　1. Skin deficiency:The skin and subcutaneous tissue on the adjacent sides of the syndactyly are less than normal, with the most obvious deficiency in the skin of the web area at the base of the fingers.

　　2. Skeletal deformities:The fingers and metacarpals, as well as the corresponding joints, in cases of mild syndactyly are normal. Skeletal deformities in complex syndactyly are divided into primary skeletal deformities and secondary skeletal deformities.

　　(1) Primary skeletal deformities: These present in a variety of forms, including bone fusion between two or more digits, developmental abnormalities of the phalanges and/or metacarpals, fusion or stiffness of interphalangeal joints, the presence of triangular phalanges, or polydactyly. These conditions are more common in syndactyly deformities of split-hand.

　　(2) Secondary skeletal deformities: These are caused by deformities in the phalanges or metacarpals, leading to static or dynamic force influences that limit the growth of the bone. This impact can be bone fusion deformities, causing delayed growth or changes in growth direction of the phalanges; or soft tissue traction can cause insufficient length of the fingers and metacarpals, joint malalignment, or flexural deformities, etc.

　　3. Vascular and nerve deformities:So far, the regularity of the deformity has not been understood. Vessels and nerves are sometimes normal and sometimes deformed or absent on one side. Therefore, when there are multiple fingers in syndactyly, it is not possible to separate multiple fingers at once to prevent vascular deformity and the necrosis of the separated fingers. Even for simple syndactyly, there may be finger vascular deformities, which can cause the tip of the finger to necrotize after the separation surgery. This vascular deformity is difficult to detect before surgery, and using laser or Doppler ultrasound, or magnetic resonance imaging can help determine the presence or absence of the artery condition of the connected fingers.

　　1. The treatment of syndactyly deformity is prone to infection.

　　2. Transplant or skin graft maceration.

　　3. Transplant destruction.

　　4. Reforming the web.

　　Experts remind: To effectively avoid complications after the correction of syndactyly deformity, postoperative care is very important. Pay attention to not getting wet in the short term, avoiding spicy foods, and other issues that need to be addressed. To prevent complications, the elbow should be屈肘90 degrees, protected by a long arm tubular cast, and avoid getting the cast or dressing wet in the bathtub or swimming pool. In addition, finding a professional doctor with rich technical experience in a regular hospital is the fundamental solution to eliminate postoperative hidden dangers.

　　The clinical manifestations of syndactyly are diverse. In form, some are skin and soft tissue syndactyly, and some are bony syndactyly where bones are fused together. It can be a single occurrence of syndactyly deformity, or one of the symptoms of other deformities, such as Apert syndrome, cleft hand deformity, and brachydactyly. It often manifests as two fingers being connected, but also three, four, or even five fingers connected. The most common is the middle ring finger syndactyly (50%), followed by the ring and small finger (30%), and the index and middle finger (15%). Thumb and index finger syndactyly is rare (5%), and about half of the children have bilateral syndactyly. The degree of finger fusion also varies, with some being partially fused, some completely fused; some only showing a longer web, some showing two fingers fused in a crisscross pattern; some have only one muscle, nerve, and vascular bundle in the syndactyly; some have two fingers closely connected, with the distal phalanx and nail also fused together; and some have the metacarpal bones fused into one but are rather large.

　　The symptoms of simple syndactyly, in addition to the damage to the appearance, mainly hinder the expansion and retraction of the fingers. The damage of complex syndactyly varies with the condition of the lesion, showing different symptoms. In congenital hand deformities, syndactyly is very common, such as polydactyly, brachydactyly, bifid hand deformity, cross-finger deformity, limb annular stenosis with syndactyly, hypoplasia of hand and syndactyly, Apert syndrome, Poland syndrome, and so on.

　　So far, there is no specific location that can explain the origin of the disease, and it is generally believed to be caused by autosomal dominant inheritance or gene mutation. Therefore, it is usually from this direction that preventive and related measures are implemented. Below, the authoritative experts from the Dajiang Health Network will give us a detailed introduction.

　　Pregnant women from pre-pregnancy to delivery mainly include the following aspects:

　　1. Marriage examination:Pre-marital physical examinations have a positive role in preventing malformations, and this is closely related to the items checked, mainly including: serological tests (such as hepatitis B virus, syphilis spirochete, HIV, etc.), reproductive system examinations, general physical examinations, family medical history, personal medical history, and genetic counseling. These are all very important factors, so pre-marital physical examinations play a prominent role in preventing malformations.

　　2. Avoid harm:Many external factors have a significant impact on the occurrence of fetal malformations, and pregnant women need to pay special attention. For example, alcohol, smoke, drugs, pesticides, noise, volatile harmful gases, toxic and harmful heavy metals, external radiation, and so on. Especially during pregnancy, health care work needs to be done well. Regular ultrasound examinations and serological screenings should be conducted, and chromosomal routine tests may be necessary at times.

　　If abnormalities are found during the examination, it is necessary to consider whether to terminate the pregnancy, the safety of the fetus, whether the fetus will have sequelae after birth, and how to prevent and treat them, among other factors. These are all issues that need to be considered.

　　Genetic testing should be performed for syndactyly malformation to determine whether it is a familial hereditary disease.

　　In addition, after admission, the most important thing for patients with syndactyly malformation is to ensure that all necessary preoperative examinations are carried out, including blood tests, urine routine tests, blood routine tests, electrocardiogram tests, chest X-ray透视 examinations, and X-ray film examinations of the affected hand.

　　A reasonable diet should include a variety of high-fiber foods, fresh vegetables, and fruits, ensuring a balanced nutrition that includes proteins, sugars, fats, vitamins, trace elements, and dietary fiber, among other essential nutrients. The combination of meat and vegetables should be diverse, fully utilizing the complementary effects of nutrients between foods.

　　Congenital syndactyly usually requires surgical treatment. The purpose of surgical correction of syndactyly is to establish a satisfactory web shape and to avoid secondary flexion contracture of the fingers. Although the separation of syndactyly is not an extremely complex surgery, it often does not achieve the expected results due to a lack of attention to its treatment principles and techniques. Infants and young children have very short fingers, which makes it difficult to design flaps and perform skin grafting and postoperative fixation. Moreover, since hand development is relatively fast, postoperative scars may contract and not adapt to the growth of the hand, necessitating secondary or multiple surgeries for repair. Therefore, syndactyly that has little functional impact and does not significantly hinder development should not be operated on prematurely. Conversely, for syndactyly that has a greater functional impact or significantly hinders development, such as distal syndactyly, the timing of surgery can be appropriately advanced. For syndactyly with very close fusion that may cause large defects in the joint capsule after finger separation, which could worsen functional disability postoperatively, it may also be unnecessary to treat. Multiple-finger syndactyly should be treated in stages for safety. Specific surgeries need to follow the following principles:

　　1. Timing of surgery The timing for the treatment of syndactyly deformities should be determined according to the form and degree of the deformity, the general health condition of the child, the safety of anesthesia, and the requirements of the parents. Early surgery can accelerate the growth rate of the child's fingers, while delayed surgery can result in obvious residual deformities. For those syndactylies where the joints are not at the same level, affecting the flexion and extension of the fingers, and for those with the distal phalanges fused together, if not separated in time, it will affect the development and function of the fingers, surgery can be performed at the age of 3-4 years. For simple incomplete syndactylies involving two or three fingers, due to the simplicity of the surgery and the need for no long-term fixation after surgery, surgery can also be performed within 6 months. Complex syndactylies involving skeletal fusion also grow with the growth process, rarely causing shortness or flexion deformities. Moreover, there are many variations in the blood vessels, nerves, and tendons of complex syndactylies, and the difficulty and risk of surgery are greater at an early age. Therefore, surgery is best performed after the age of 3-4 years.

　　2. Complete separation of the fingers The separation of the fingers should be carried out thoroughly during the operation of separating the fused fingers, and the fingers should be completely separated to the normal web base. If the base of the web is not completely separated, part of the fused fingers will remain. The normal web should have a considerable width and length of oblique skin folds, accounting for 1/3 to 1/2 of the length of the middle phalanx.

　　3. Reconstruction of the interdigital web The interdigital web of a normal adult starts from the distal dorsal aspect of the metacarpal head and slopes towards the palmar side, connecting with the palmar skin at the transverse crease of the palm, with a width of about 1 cm. Good reconstruction of the interdigital web during the separation operation is a key factor. There are many surgical techniques for shaping the web, among which the most commonly used are the paired triangular skin flaps on the dorsal and palmar sides of the web base, rectangular flaps, lingual skin grafting, and unilateral triangular skin flap repair, etc., which are sutured together to form a new web. Among them, the rectangular flap method is more in line with physiology and has a good effect. The triangular flap method for reconstructing the web is not suitable for routine use due to the high risk of necrosis at the tip of the flap and the scar left in the middle of the web.

　　4. Grit-like incisions and skin grafting: The skin between the fingers should be incised in a grit-like manner to avoid straight-line incisions, otherwise, it may result in linear scar contracture. When designing the grit-like skin flaps, the location of the flaps should be designed according to different situations, usually the flaps should cover the joint area as much as possible. After the fingers are separated, the wound cannot be closed under tension, and full-thickness skin grafting should be used to avoid the widening and increase of scars, or even the necrosis of the local skin, or even the necrosis of the entire finger. From the perspective of finger function, in order to make the radial side of the main fingers feel good, attention should be paid to cover the radial side of the fingers with flaps as much as possible when designing the surgical incision, leaving the defect on the ulnar side of the other finger, and repairing it with skin grafting.

　　5. For fused fingers with fused distal phalanges, when separating the distal part, it is necessary to simultaneously take a skin flap and a subcutaneous tissue fascia flap locally on the palm, and they should be staggered to cover the two exposed bony surfaces, paying attention to their blood circulation. Then, skin grafting is performed on the subcutaneous tissue flap, and the pressure packing force should not be too large to avoid necrosis of the fascia flap due to excessive pressure. For the exposed distal phalanx bone, a local skin flap should be used for coverage, and if there is soft tissue coverage around it, skin grafting can also be used for repair.

　　6. The treatment of the ends of completely fused fingers, the repair of the skin and nail edge of the fused fingers can be performed using the method described by Buck-Gramcko, which is beneficial to the shape and growth of the nails.

　　7. Simple incomplete fusion of two fingers can be completed in one stage of surgery; for cases that require multiple surgeries, the order of surgery should be arranged to correct bone deformities, correct deformities of the thumb and index finger first, and correct the fusion of the middle and ring fingers or the ring and little fingers later. For multiple fused fingers, staged surgery for correction should be performed, first separating the fingers connected in the middle, and then separating the adjacent fingers later, in order to avoid ischemic necrosis of the middle fingers. For complex fused fingers, the main operation is to separate the fused fingers, and other deformities are dealt with accordingly. The operation should be performed carefully, starting from the proximal part to separate the connected soft tissues, and finally separating the osseous fusion and the nail, removing excess bone, and trying to cover it with skin flaps.

　　8. Treatment of blood vessels, nerves, and tendons, and deformities where fingers or multiple fingers are fused together, often accompanied by vascular and nerve variations. It is necessary to consider these factors fully before surgery, and if possible, a vascular angiography should be performed to fully understand the blood vessel condition. Considering the tendons and nerves, etc., then perform surgery. When the blood supply of multiple fused fingers is poor, the method of staged surgery for separation can be adopted. When there is only one digital nerve between two fused fingers, the nerve should be retained as much as possible on the radial side of the index, middle, and ring fingers, and on the ulnar side of the little finger, in order to reconstruct the sensation during the pinch. When two fused fingers share one tendon, the tendon can be retained on the main finger, and if necessary, it can be transferred from one finger to the corresponding position on the main finger. For fingers without tendons, a tendon transplantation can be performed later.