Developmental dysplasia of the hip (ddh), also known as developmental hip dysplasia, is a common hip disorder in pediatric orthopedics, with an incidence of about 1 in 1,000, six times the incidence in female infants compared to male infants, twice the incidence on the left side compared to the right side, and about 35% bilaterally. ddh includes hip dislocation, subluxation, and acetabular dysplasia. The causes are multifactorial, girls, first births, multiple births, family history, poor fetal position, breech position, low amniotic fluid, combination of clubbed neck and clubfoot, and incorrect swaddling such as candle wrapping. Depending on the age of the child, degree of dislocation, unilateral or bilateral onset, etc., the following manifestations may be present Bilateral hip circumference asymmetry. Positive left abduction test Positive allis sign Auxiliary examination Ultrasonography is most suitable for Graf method Advantages: high specificity and sensitivity, diagnostic for both subluxation and subluxation with acetabular dysplasia, dynamic observation and no radioactivity. Disadvantages: high variability of results. X-ray examination is more suitable for children from 5 months to 6 months old. Acetabular index below 25 degrees is normal, those with greater than 25 degrees to 30 degrees are closely observed and dynamically reviewed, and those with greater than 30 degrees need clinical intervention.