Developmental hip dislocation (formerly called congenital hip dislocation) is one of the common diseases in orthopaedic surgery, with more females than males, twice as many on the left side than on the right side, and less on the bilateral side. The incidence is high in China, and early diagnosis and treatment can yield the best results. There are several etiological theories, but they are still not clear. At birth, the joint capsule of infants is loose, but there are no other anatomical abnormalities, after birth, the acetabulum becomes shallow, the direction is posterior, the glenoid lip composed of the joint capsule and acetabular cartilage is thickened and turned inward; the development of the femoral head is delayed and small, the anterior inclination angle of the femoral neck increases, and in the late stage, the joint capsule is displaced, thickened, deformed and adhered, the iliopsoas muscle, the adductor muscle, the rectus abdominis muscle The contracture of iliopsoas muscle, adductor muscle, rectus abdominis muscle, etc. appears. (1) Congenital hip dislocation in neonates and infants 1. Congenital hip dislocation is difficult to diagnose in the neonatal period, but once it is diagnosed, it is easy to treat and obtain ideal treatment results. Because the pathological changes in the neonatal period are the lightest and easy to correct; the pelvis develops fastest in the first year after birth, especially in the neonatal period. 2. Clinical symptoms Appearance: asymmetry between thighs and calves and the opposite side, which may be manifested as thickening and shortening or thinning and external rotation (unilateral); widening of the buttocks (bilateral). Skin lines: increased, deepened and asymmetrical upward movement of skin lines on the buttocks, groin and thighs. Limb movement: the affected limb has little movement and is most easily detected during diaper changes. 3. Signs: weakened or absent femoral artery of the affected limb; tense spasm of the adductor muscle; positive Barlow’s test (only for neonates), as hip instability decreases with increasing age, while abduction restriction increases with increasing age. Positive Ortolani’s sign or abduction test, which is reliable. Nelaton’s line sign is destroyed. 4.Auxiliary examination: less than 4 months, ultrasound determination of alpha, beta angle, >4 months X-ray examination can confirm the diagnosis. (2) Children in childhood have a swaying, limping gait with posterior hip convexity and increased anterior arch of the lumbar spine. The child is lying down, the examiner fixes the pelvis with one hand, lifts the femur with the other hand and abducts the affected hip, there is a popping sound, indicating reset, the hand is relaxed and pops out again. x-ray pelvic film, the femoral head is seen to be small and not in the acetabulum, the acetabular index is increased, the stem angle of the femoral neck is straightened and increased, the Shenton’s line is not The Shenton’s line is not continuous. (1) Hip dysplasia: also known as hip instability, the x-ray is often characterized by an increase in the acetabular index, most of which are self-healing with an external hip booth, about 1/10 will develop into congenital hip dislocation in the future, and a few cases persist with acetabular dysplasia and symptoms appear when they grow older. (2) Hip subluxation: X-ray has an increased acetabular index with the acetabulum covering part of the femoral head, which is an independent type that can persist for a long time without transforming into total dislocation. (3) Total dislocation of the hip joint: the femoral head is completely dislocated from the acetabulum, which can be divided into four degrees according to the height of the dislocation of the femoral head: Ⅰ degree: the femoral head is only displaced outward and located at the same level of the acetabulum; Ⅱ degree: the femoral head is displaced outward and upward, which is equivalent to the level of the outer upper part of the acetabulum; Ⅲ the dislocated femoral head is located at the part of the iliac wing; Ⅳ the dislocated femoral head is displaced upward to the level of the sacroiliac joint. 2.Deformed congenital hip dislocation Typically, both hips are dislocated, both knees are stiff in the extension position and cannot be flexed, both feet are flat-footed in the external rotation position, and the upper limbs are often combined with deformities. Treatment (1) early diagnosis, should be from the delivery hospital, the beginning of the examination, found that the treatment. The younger the age, the easier and more effective the treatment method. (2) The principle of treatment is easy first, then difficult. (1) When the child is <6 months old, it can be treated with Pavlik sling; (2) When the child is around 6 months-2 years old, it is often treated with percutaneous internal muscle release with closed repositioning and frog plaster or brace; (3) When the child is over 2 years old and the child fails to be repositioned manually, it should be treated surgically. There are many surgical methods, so we do not simply emphasize one surgical method, but should choose the best surgical method by taking into account the specific situation of the child and the mastery of various surgical methods by each physician.