What are the imaging guidelines for hip evaluation in infants?

From the Guidelines

Ultrasound screening is the recommended initial imaging modality for infants with suspected developmental dysplasia of the hip (DDH) between 4 weeks to 4 months of age. According to the American College of Radiology [ 1 ], imaging is not recommended for the initial imaging of children younger than 4 weeks of age with an equivocal physical examination or risk factors shown for DDH.

Key Considerations

• For infants with clinically unstable hips, immediate ultrasound is warranted [ 1 ].
• Follow-up imaging should occur at 6-week intervals until normalization or until 4-6 months of age, when plain radiographs become more appropriate as ossification of the femoral head progresses [ 1 ].
• The Graf classification system is commonly used to categorize hip development on ultrasound, with types I and IIa considered normal or immature normal, while types IIb, IIc, D, III, and IV represent progressive dysplasia requiring intervention.

Imaging Guidelines

• Ultrasound screening is recommended at 6 weeks of age for those with risk factors (breech presentation, family history of DDH, or abnormal physical exam) [ 1 ].
• Pelvic radiography becomes the preferred confirmatory imaging modality after the appearance of the ossific nucleus, allowing for the assessment of the femoral head ossific nucleus, the development of the proximal femur, and bony acetabular morphology [ 1 ].

Importance of Early Detection

• Early detection through appropriate imaging is crucial as treatment is most effective when initiated before 6 months of age, typically involving Pavlik harness therapy for younger infants and more invasive interventions for older children with persistent dysplasia [ 1 ].
• Delayed diagnosis can lead to complications including early osteoarthritis, gait abnormalities, and the need for surgical correction.

From the Research

Imaging Guidelines for Hip Evaluation in Infants

The imaging guidelines for hip evaluation in infants vary based on age and risk factors.

• For infants younger than 4 months, screening hip ultrasound (US) is recommended only for those with risk factors, equivocal or positive exam findings 2.
• For infants older than 4-6 months, pelvis radiography is preferred 2.
• The use of ultrasound in evaluation of infant's hip development can reduce surgical procedures, hospitalization and late presentation of developmental dysplasia of the hip (DDH) 3.
• Radiographic assessment of every sonographic positive hip is recommended in infants older than 3 months 3.

Imaging Modalities

Different imaging modalities are used for hip evaluation in infants, including:

• Ultrasound: effective in children up to one year of age and should be used in place of most roentgenograms 4.
• Radiography: used for infants older than 4-6 months and for radiographic assessment of every sonographic positive hip 2, 3.
• Magnetic Resonance (MR) Imaging: preferred over computed tomography (CT) for follow-up after surgical hip reduction, as it can confirm concentric hip joint reduction and identify soft-tissue barriers to reduction and postoperative complications 2.

Detection of Developmental Dysplasia of the Hip (DDH)

DDH can be detected using:

• Hip examination and ultrasound in newborns, especially when risk factors or clinical features suggestive of DDH are present 5.
• Sonography of hip dysplasia, which can detect DDH early and reduce the incidence of long-term complications 6.