What is the optimal time to perform a hip ultrasound for hip click assessment in infants?

Optimal Timing for Hip Ultrasound in Infants with Hip Click

Direct Recommendation

For infants with an isolated hip click (stable clicking hip without instability on Barlow or Ortolani testing), perform hip ultrasound at 4-6 weeks of age, not earlier. 1

Understanding Hip Click vs. Hip Instability

A stable "clicking" hip represents a hip with no laxity but with an audible or palpable "click" on physical examination, which is fundamentally different from true instability detected by Ortolani or Barlow maneuvers. 2 The distinction is critical:

• True instability (positive Ortolani or Barlow test) requires ultrasound evaluation and warrants earlier orthopedic attention 1
• Stable hip click without laxity is a common finding that often resolves spontaneously 2

Timing Algorithm for Hip Ultrasound

Before 2 Weeks of Age: NOT RECOMMENDED

• Ultrasound performed before 2 weeks has unacceptably high false-positive rates due to physiologic laxity 1
• Hip instability often resolves spontaneously by 2 weeks of age 1
• Early imaging leads to overdiagnosis and unnecessary treatment 1, 3

At 4-6 Weeks of Age: OPTIMAL TIMING

• The American Academy of Pediatrics recommends initial ultrasound screening at 4-6 weeks of age for high-risk infants and those with examination concerns 1
• By this age, the hip has "shown its true nature" and transient physiologic findings have resolved 4, 5
• This timing balances early detection with avoidance of false positives 5
• 84-95% of mildly abnormal hips normalize by 3 months without treatment, making this window ideal for identifying hips that truly require intervention 1

After 4 Months of Age: TRANSITION TO X-RAY

• Ultrasound remains the preferred modality under 4 months of age 1, 3
• After 4-6 months, radiographs become more reliable as the femoral head ossific nucleus appears and sufficient ossification occurs 2, 1
• X-rays before 4 months have limited value due to the largely cartilaginous hip structures 2, 1

Clinical Context for Hip Click

The sensitivity and specificity of clinical examination depend heavily on examiner expertise. 2 For a stable clicking hip specifically:

• Continue routine physical examination at all well-baby visits (1-2 weeks, 2,4,6,9, and 12 months) 2
• If the click persists or examination findings become equivocal, ultrasound at 4-6 weeks is indicated 1
• Normal physical examination does not completely exclude the possibility of developing dysplasia, making appropriate imaging follow-up important 3

Common Pitfalls to Avoid

• Do not image too early: Ultrasound before 2 weeks leads to overtreatment of physiologically immature hips, which can cause complications including avascular necrosis of the femoral head 1, 3
• Do not confuse stable click with instability: A stable click without demonstrable laxity on Barlow/Ortolani testing does not automatically require immediate imaging 2
• Do not rely solely on clinical exam: While most clicks are benign, persistent findings warrant imaging to avoid missing progressive dysplasia 3
• Do not use x-rays in young infants: Radiographs have limited value before 4-6 months due to delayed ossification 2, 1

Special Populations Requiring Earlier Attention

Even with a stable hip click, certain risk factors warrant ultrasound at 4-6 weeks regardless of examination findings: 1

• Female infants born in breech presentation 1
• Male infants born in breech presentation 1
• Family history of DDH 3
• Positive Barlow or Ortolani test (requires immediate orthopedic referral, not just scheduled ultrasound) 1

Prematurity Considerations

For moderate preterm and near-term infants (born at <37 weeks gestation), screening ultrasounds can be performed at 5-8 weeks of unadjusted chronological age without adjusting for gestational age. 6 There is no significant difference in alpha angle or femoral head coverage between premature and full-term patients at this timing. 6