Congenital hip dislocation, also known as developmental hip dislocation, is a lesion that has a significant impact on children’s health and is one of the main diseases that cause physical disability in children. After the age of 2 years, children with hip dislocation on both sides of the pelvis can walk with a very pronounced handful of movements on both sides, with the hips protruding backward and the lumbar vertebrae protruding forward, which is called a duck-step wobbling posture. Three theories have been proposed for the etiology of developmental hip dislocation: 1, mechanical theory: fetal malposition and breech delivery make the hip joint suffer mechanical pressure in an abnormal flexion position, which easily causes dislocation of the femoral head. It has been reported in the literature that, according to local traditions and customs, wrapping the baby in swaddling clothes to force the hip joint to be in a straight position can increase the incidence of congenital hip dysplasia. 2, hormonal theory (causing joint laxity): women are affected by estrogen during childbirth, producing pelvic ligament laxity; and the fetus in utero is also affected, causing ligament laxity, making the newborn prone to femoral head dislocation. 3, primary systemic dysplasia and genetic theory: Wynne-Davies reported that a family line all had shallow acetabular performance, suggesting that primary acetabular dysplasia may be a risk factor for congenital hip dysplasia. ortolani observed the risk of genetic factors, and reported that 70% of children with congenital hip dysplasia had a positive family history. Early diagnosis and early treatment of developmental hip dislocation should be emphasized, with the best results in infancy and worse results at older ages. Warning: It is generally believed that treatment after 2 to 3 years of age, even if very successful, will result in hip pain after 35 years of age. Therefore, most scholars emphasize the need for screening of newborns so that early diagnosis and treatment are important measures to obtain a cure. Clinical examination is the first step of diagnosis, it can only indicate that there is a problem with the hip joint, but the final diagnosis needs to be made by X-ray examination. Related X-ray examinations 1. Conventional orthopantomographs of the pelvis: within 6 months after birth, the epiphyseal ossification center of the femoral head has not yet appeared in most children, and the combination of orthopantomographs of bilateral hip joints and bilateral hip frog positions is needed to make the diagnosis. For children over 6 months of age, the diagnosis can be confirmed by taking orthopantomographies of the hip joints bilaterally after the ossification centers have appeared. CT and MRI examinations are also important for developmental hip dislocation in older children: CT can evaluate the bony condition of the femoral head and acetabulum, and measure the anterior tilt angle of the femoral head and the stem angle of the femoral head and neck; MRI can observe the cartilage in the hip joint: the cartilage of the femoral head and acetabular cartilage, the round ligament and the glenoid lip.