Imaging for an 8-Month-Old with Suspected Developmental Dysplasia of the Hip (DDH)
For an 8-month-old infant with suspected developmental dysplasia of the hip (DDH), pelvic radiography is the preferred initial imaging modality as it allows assessment of the femoral head ossific nucleus, proximal femur development, and bony acetabular morphology. 1
Rationale for Pelvic Radiography at 8 Months
- By 8 months of age, the ossific nucleus of the femoral head has typically appeared in most infants (normal range 1.5-8 months), making radiographs more useful than they would be in younger infants 1
- The American College of Radiology recommends:
- Ultrasound for infants 4 weeks to 4 months
- Radiograph of the pelvis for infants 4-6 months and older 2
- At 8 months, clinical assessment alone is less reliable, and imaging is necessary to confirm diagnosis 1
Limitations of Ultrasound at This Age
- The American Academy of Pediatrics (AAP) and American Academy of Orthopedic Surgeons (AAOS) do not advocate ultrasound for DDH screening after 4-5 months 1
- Studies show that ultrasound may overdiagnose DDH in patients 4-6 months of age, with one study finding a 40% overdiagnosis rate when compared to radiographs 1
Benefits of Radiography at This Age
- Allows assessment of:
- Femoral head ossific nucleus position and development
- Proximal femur development
- Bony acetabular morphology 1
- Can reliably exclude DDH in children with risk factors 1
- Reduces unnecessary follow-ups and potential iatrogenic treatment complications 1
Special Considerations
- In dysplastic hips, the appearance of the ossific nucleus is often delayed and may appear eccentric 1
- If the infant is currently undergoing treatment with a Pavlik harness, positioning for radiographs may be suboptimal 1
- While a 2019 study suggested ultrasound could be an alternative to X-ray for 6-month-olds 3, current guidelines still recommend radiography as the standard of care for 8-month-old infants 1, 2
Treatment Implications of Imaging Findings
- Imaging results will guide treatment decisions:
- For an 8-month-old, surgical intervention may be necessary if severe dysplasia or dislocation is identified, as the Pavlik harness is most effective when applied before 6 weeks and typically only used up to 6 months of age 1, 2
- Regular radiographic assessment will be necessary to monitor for residual dysplasia 2
Common Pitfalls to Avoid
- Relying solely on clinical examination at this age - limited hip abduction has variable reliability as a screening method 1
- Using ultrasound as the primary imaging modality at 8 months - may lead to overdiagnosis and unnecessary treatment 1
- Delaying imaging - late diagnosis can lead to poorer outcomes and may require more invasive interventions 4