What prompts a physician to order a hip ultrasound in a baby at one or two months of age?

Indications for Hip Ultrasound in 1-2 Month Old Infants

Hip ultrasound in 1-2 month old infants is primarily indicated for infants with risk factors for developmental dysplasia of the hip (DDH) or abnormal physical examination findings, as recommended by the American Academy of Pediatrics (AAP). 1, 2

Primary Indications for Hip Ultrasound at 1-2 Months

• Risk factors requiring ultrasound screening (even with normal physical exam):

  • Female infants born in breech presentation (highest risk group) 1
  • Male infants born in breech presentation 1
  • Female infants with positive family history of DDH 1, 2
  • Inconclusive or equivocal physical examination findings 1

• Abnormal physical examination findings:

  • Positive Barlow test (dislocatable hip) 1
  • Positive Ortolani test (relocatable hip) 1
  • Limited hip abduction 3
  • Hip click or clunk 4

Optimal Timing for Ultrasound

• 4-6 weeks of age is the recommended timing for initial ultrasound screening in high-risk infants 1, 2

• Ultrasound before 2 weeks of age is not recommended due to:

  • High false-positive rates from physiologic laxity 1
  • Risk of overdiagnosis and unnecessary treatment 1
  • Hip instability often resolves spontaneously by 2 weeks 1, 2

• For premature infants, screening can be performed at 5-8 weeks of chronological age without adjustment for gestational age 4

Rationale for Ultrasound vs. X-ray at This Age

• Ultrasound is the preferred imaging modality for infants under 4 months 1, 2
• X-rays have limited value before 4-6 months due to:
  • Delayed appearance of femoral head ossific nucleus 1
  • Largely cartilaginous acetabular margin 1
  • Difficulty in assessing acetabular morphology and femoral alignment 1

Clinical Considerations

• Universal ultrasound screening is not recommended due to high rates of spontaneous normalization 1, 5
• Selective screening of high-risk infants is the standard approach 1, 2
• 84-95% of mildly abnormal hips (Graf type II) normalize by 3 months without treatment 1
• Delayed diagnosis beyond 6 months often requires surgical correction rather than non-invasive treatments 1

Follow-up Recommendations

• Infants with abnormal ultrasound findings may require:

  • Treatment with abduction devices (Pavlik harness) 6
  • Serial ultrasound monitoring to assess treatment response 1
  • Transition to radiographic monitoring at 4-6 months 2, 6

• Even with normal initial screening, all infants should have hip examinations during regular well-baby visits at 2 weeks, 2 months, 4 months, 6 months, 9 months, and 1 year 3

Hip ultrasound at 1-2 months represents an optimal balance between allowing time for spontaneous resolution of neonatal hip laxity while still enabling early intervention when needed to prevent long-term complications of DDH.