In the early diagnosis and treatment of DDH, a standard orthopantomogram of the pelvis is often required. A substandard x-ray may affect the doctor’s ability to make accurate judgments and may even affect treatment as a result. Is there any impact on the baby’s health when the child is so young to have an X-ray? For the diagnosis of hip dysplasia/developmental hip dislocation, hip ultrasound is the main diagnosis below 4 months of age, and standard pelvic X-ray is the main diagnosis above 4 months of age (especially for babies whose femoral head ossification nucleus has already appeared). The current domestic and international opinion is that similar diagnostic need for X-ray taking will not have any effect on the child’s health. How to take a standard orthopantomogram of the pelvis? For parents who need to take a radiograph to understand the development of the hip joint, they need to know how to position the child during the radiograph: have the baby lie on his or her back with the lower limbs naturally extended shoulder-width apart (the midline of the body passes through the middle of the legs), the patella (knees) bilaterally forward, and the lower limbs internally rotated so that the tips of the feet are opposite each other (internal rotation of about 15°). In children under 6 to 8 months of age, there is often a degree of physiological flexion contracture of the hip joint (which is normal development), therefore, mild hip flexion (approximately 30°) can be maintained during the radiograph without completely flattening both lower limbs. Left: One person holds the baby’s armpit to control the twisting while one person holds both lower legs during the filming, with the thumb pressed on the patella to make sure the patella is facing upward, keeping the hips naturally lying flat and both lower limbs naturally straight, taking care not to press down hard to avoid causing the child’s hips to buckle. Right: The larger child lies naturally flat with both lower limbs internally rotated so that the toes are opposite each other. Is this a standard orthopantomogram of the pelvis? Commonly used methods include: whether the tip of the coccyx is facing the pubic symphysis; whether there is symmetry between the closed foramina and the iliac wing on both sides; whether there is significant adduction/abduction of both lower limbs; whether there is significant rotation of both lower limbs (usually easy to externally rotate, when the lower limbs are externally rotated, the proximal femur has a prominent medial lesser trochanter and the lateral greater trochanter becomes smaller). 3 years old boy in different positions: left picture: excessive external rotation of both lower limbs (lesser trochanter is obvious); The right image is a standard orthopantomogram of the pelvis.