The thorax consists of a skeletal framework composed of the spine, ribs and sternum. Skeletal abnormalities due to congenital development can cause different types of thoracic deformities, among which funnel chest and pectus excavatum are more common, while sternal cleft and rib developmental deformities are less common. A. Funnel chest Funnel chest (pectus excavatum) is the most common congenital chest wall deformity, the incidence of foreign reports in 1 ‰ to 2 ‰, the incidence of Asia is higher than in Europe and the United States, China has scattered incidence throughout the country. The main feature is the dorsal inclination and depression of the sternal body from the lower edge of the sternal stalk to the upper edge of the saber, with the lower rib cartilage on both sides also bending dorsally, making the lower part of the anterior chest funnel-shaped, with the apex of the depression usually at the intersection of the lower sternal body and the saber. 1, etiology The etiology of funnel chest is still unclear. Although rickets can be caused, most of them are congenital developmental abnormalities. Some scholars believe that the central tendon of the diaphragm is too short and pulls the end of the sternum and the saber process. Some scholars believe that during fetal development, the sternum and ribs are unbalanced and the rib cartilage is overgrown, and the overgrown rib cartilage bends backward, causing the chest wall to depress and form a funnel chest. Recent studies have shown that genetic factors are one of the important causes. In children with severe rickets, congenital tracheomalacia, upper airway stenosis, and asthma, the rib cartilage can be sunken with breathing to form the funnel chest sign. 2.Pathology Due to the progressive inward and backward depression of the lower end of the sternal body, the anterior and posterior diameter of the thorax is shortened, resulting in compression of the intrathoracic organs and displacement of the heart to the left, which can affect the heart diastole. The heart is displaced to the left, which may affect the heart diastole. Both lungs are also pressed inward due to the thorax, which affects the pulmonary ventilation function and is often prone to lung infection. According to the appearance of funnel chest deformity and the scope and depth of depression, funnel chest can be divided into extensive type, limited type, symmetrical type and asymmetrical type. The extensive type is often combined with a flat chest, and the anterior and posterior diameter of the chest cavity is generally shortened, making the middle anterior chest depression appear shallow and wide. The depth of sternal depression varies, and in severe cases, the raphe may be close to the anterior edge of the thoracic vertebrae. All the above types can be accompanied by sternal rotation, rib edge exostosis, and sternal rotation can lead to different heights of chest wall on both sides. 3.Clinical manifestations Most children with funnel chest have shallow depressions in the chest shortly after birth, and most of them are obvious at the saber process. Since the subcutaneous fat is more plump in infants, it is not easy to be detected. Later on, as the child grows older, the anterior chest depression deepens or becomes clearer at the age of 1 to 4 years, and basically stabilizes at the age of 4 to 6 years, and is often accompanied by flattening of the chest in those with aggravation after school age. Mild concave deformity may be asymptomatic. In those with significant depression, upper respiratory tract infections often occur because of the compression of the chest wall on the heart and lungs, restricted gas exchange and retention of secretions in the lungs. Most children have symptoms of reduced exercise tolerance, palpitations and shortness of breath after a little physical activity, but it is uncommon for the heart and lung function to be seriously affected. These children are often ashamed to expose their foreheads in public, afraid to wear tank tops in summer, afraid to take baths in public bathrooms, afraid to go swimming, and some even form psychological isolation. Physical examination: generally are thinner and shorter than children of the same age. The lower part of the anterior chest can be seen to be sunken inward and backward in the shape of a funnel chest, which can be accompanied by rib deformity, the center of the funnel can be in the center line or slightly oblique, and the apical pulsation is shifted to the left. Physical changes can be seen in the form of anterior shoulder tilt, posterior back arch, anterior chest concavity, and abdominal bulge, which are called funnel chest signs. Some children also have pectoral dysplasia, flat chest, etc. The chest X-ray shows that the lower part of the sternum and the adjacent rib cartilage are obviously sunken, the sternal body is obviously bent backward in the lateral chest X-ray, the spine and sternal spacing is shortened, and the lower part of the sternum can reach the anterior edge of the spinal vertebrae in some cases. The heart shadow is mostly displaced to the left side of the chest cavity, and there is an obvious radiolucent translucent area in the middle of the heart shadow, and the right heart margin often overlaps with the spine; individual patients with severe heart shadow can be completely located in the left chest cavity, and older patients have more lateral curvature of the spine. CT scan of the chest: It can clearly show the degree and extent of anterior thoracic depression and the compression of the heart and lungs. An electrocardiogram (ECG) examination may show a translocation of the heart under pressure, T-wave changes, and in severe cases, ventricular hypertrophy. Other tests, such as echocardiography and pulmonary function tests, can be used to assess preoperative cardiopulmonary function. 4.Treatment Surgery is the only effective method to treat funnel chest. The objectives of surgical treatment are: (1) to correct chest wall deformity, relieve cardiopulmonary compression, and improve cardiopulmonary function; (2) to prevent the continued development of funnel chest signs; (3) to relieve the child’s psychological barriers. Indications for surgery: Surgery should be performed if the funnel chest affects cardiopulmonary function and has a psychological burden, and surgery should be performed if the Haller index is greater than 3.2 or if the funnel index is greater than 0.2. It is generally believed that the appropriate age for surgical correction is 4 to 12 years old, when the child has good flexibility and elasticity of the thorax and good compliance, which facilitates intraoperative operation and postoperative recovery and treatment. Most scholars believe that children within 3 years of age should be followed up as long as there is no obvious cardiopulmonary dysfunction, due to weakness, soft bones and easy deformation of rib cartilage (active rickets), and that there is hope for self-correction. (1) Haller index is the ratio of the transverse diameter and anterior-posterior diameter of the most depressed part of the thorax on CT scan, which can accurately calculate the degree of thoracic deformity and can be used as one of the methods to evaluate the indications for surgery. the internal diameter of the coronal surface of the chest on CT film is divided by the distance from the deepest point of the funnel to the front of the spine. In case of asymmetric funnel chest, where the lowest point of depression is not in the anterior spine, two horizontal lines are drawn at the anterior spine and the lowest point of depression, and the modified CT index is calculated according to the distance between the two lines. The average index is 2.52 for normal subjects, <3.2 for mild, 3.2-3.5 for moderate, and >3.5 for severe. (2) Funnel index (FI) is another commonly used assessment method in China. FI = (a×b×c) ÷ (A×B×C) Surgical methods: The surgical treatment of funnel chest has a history of nearly 100 years, and has experienced sternal rib resection, external traction combined with rib cartilage resection and sternal osteotomy, sternal reversal method, sternal lift and internal fixation without osteotomy, etc. (1) The representative method of osteotomy and external fixation is Gross external fixation method: its principle is to loosen the sternum and ribs under the periosteum, lift the chest wall after osteotomy and orthopedic, first suture the osteotomy break end, and then pierce the steel wire from the sternum to the skin outside for external fixation of bridge type plate. Although the postoperative appearance of the thorax has improved, but because of the postoperative children are not easy to cooperate, and external fixation is difficult to maintain the stability of the chest wall, and sometimes the steel wire fracture resulting in orthopedic failure. In addition, the method is very traumatic complications (mainly skin, bone and lung infection), so it has been rarely used after the 1960s. (2) Sternal reversal method: This surgery was invented in the 1940s. The procedure is mainly represented by Wada in Japan, in which the thorax and ribs in the depressed area are stripped and osteotomized under the periosteum and then turned over and sewn back to the original place. Some people have adopted a modified reversal procedure without cutting the rectus abdominis muscle to maintain good blood flow. Some people also perform vascular anastomosis after reversal. However, because of the long operation time, relatively large bleeding and surgical trauma, even if the rectus abdominis muscle is not cut off, it is difficult to ensure that the blood flow is not affected after the flip. Moreover, the chest wall is unstable without the addition of fixed support bars. After surgery, abnormal breathing and pulmonary complications often occurred, and the orthopedic effect was not very satisfactory, and sometimes the sternum became anteriorly convex and deformed. After the 1970s, it was replaced by the modified “sternal rib lift method”. (3) The representative method of sternal lift is the Ravitch procedure and various modified techniques, which was first reported by Ravitch in 1949. This procedure has been the most used in the past half century and was considered the most reliable method for correction of funnel chest in children. Many improvements have been made in the management of the deformed rib cartilage and its periosteum, as well as in the sternal osteotomy and internal fixation methods. A longitudinal or transverse incision is made in the chest wall depression to free the muscles, expose the deformed sternum and rib cartilage, cut and free the deformed rib cartilage membrane, and remove the excess rib cartilage bilaterally. The sternum is cut at the level of the sternal recess in a V-shape, and the posterior cortex is preserved; the recess is fixed with two stitches of PDS suture or wire suture to level the recess. A Kirschner pin or plate is also placed at the level of the posterior sternum of the fifth rib from left to right and fixed between the ribs. The rib cartilage is sutured, the periosteum is closed, and the stent is removed more than 2 years after surgery. Due to damage of rib cartilage resection, rib growth center or rib cartilage membrane, poor regeneration of rib cartilage may occur after surgery, with varying degrees of osteogenesis or calcification of the regenerated rib cartilage, non-connection of regenerated rib cartilage with the sternum, and in the most severe cases, even stiffening and narrowing of the thorax leading to restrictive ventilation disorders. (4) The representative of internal fixation without osteotomy is the Nuss procedure. 1998 Nuss firstly reported the minimally invasive thoracoscopically assisted funnel chest correction, because this procedure does not free the pectoralis major flap, does not remove the rib cartilage and does not do sternal osteotomy; the incision is small and hidden, the operation time is short, bleeding is low, and recovery is fast; the most outstanding thing is that it can maintain the chest extension, expansion, flexibility and elasticity for a long time. And because the operation is simple and easy to master, it achieves minimally invasive surgical orthopedics, and thus is rapidly accepted by surgeons in various countries. The operation method is to select a plate of suitable length and adjust the curvature according to the size of the child’s thorax, then make transverse incisions of about 2.5 cm between the anterior and posterior axillary lines of both sides of the chest wall at the same level of the lowest point of the sternal depression, insert the guide plate from the right side after the artificial pneumothorax with the assistance of thoracoscope to the opposite side, then traction guide the plate convex side backward to drag it across the back of the sternum to the right side, turn the plate 180°, so that the sternum and the anterior chest wall can be extended. The plate is then flipped 180° to make the sternum and anterior chest wall projection assume the desired shape, and finally the plate is fixed with a fixator. With the accumulation of surgical experience and continuous improvement of techniques, the Nuss procedure has become the standard procedure for the correction of funnel chest.