What is the recommended approach for diagnosing hip dysplasia in an infant?

Diagnosing Hip Dysplasia in an Infant

The diagnosis of hip dysplasia in infants relies on clinical examination at every well-baby visit, with selective ultrasound screening at 4-6 weeks for high-risk infants (female sex with breech presentation, positive family history, or abnormal physical findings), transitioning to radiography after 4-6 months of age when ossification allows reliable assessment. 1, 2

Clinical Examination Approach

Birth to 3 Months

• Perform Ortolani and Barlow maneuvers at each well-baby visit (1-2 weeks, 2,4,6,9, and 12 months) 1
• The Ortolani test detects an already dislocated hip by abducting the flexed thigh and lifting it anteriorly—a palpable "clunk" indicates the femoral head relocating into the acetabulum 1
• The Barlow test identifies unstable hips by gently adducting the thigh to dislocate the femoral head posteriorly, then abducting to relocate it 1
• These maneuvers detect ligamentous or capsular laxity between the femoral head and acetabulum 1

After 3 Months

• The Ortolani and Barlow tests become less reliable as capsule laxity decreases and muscle tightness increases 1
• Focus on limited hip abduction (the most important screening method in older infants) and asymmetric thigh folds 1
• Note that asymmetric skin folds lack specificity and should not be relied upon alone 1

Important Distinction

• A stable "clicking" hip (audible click without laxity) differs fundamentally from true instability and often resolves spontaneously—do not confuse this with a positive Ortolani or Barlow test 1, 2

Risk Factor Assessment

Elicit these high-risk factors at every examination 1, 3:

• Female sex (4-8 times more common than males) 1
• Breech presentation (especially frank breech with hip flexion and knee extension) 1
• Positive family history of DDH 1, 3
• Firstborn status 1
• Oligohydramnios 1
• Large infant size/higher birth weight 3

Imaging Strategy by Age

Before 4 Months: Ultrasound

• Perform ultrasound at 4-6 weeks (not earlier) for high-risk infants or those with abnormal physical findings 1, 2
• Ultrasound before 2 weeks has unacceptably high false-positive rates due to physiologic laxity, as 60-80% of abnormalities on physical exam and >90% on ultrasound resolve spontaneously 1, 2
• Specific indications for ultrasound 1, 2:
  • Female infants with breech presentation (strongest AAP recommendation)
  • Male infants with breech presentation
  • Positive family history in females
  • Positive Ortolani or Barlow test
  • Equivocal or inconclusive physical examination

After 4-6 Months: Radiography

• Radiographs become reliable once the femoral head ossific nucleus appears (typically 4-6 months, range 1.5-8 months) 1
• Before this age, radiographs have limited value because the femoral head is entirely cartilaginous and acetabular margins are largely cartilaginous 1
• Obtain anteroposterior pelvis radiograph to assess acetabular index, femoral head position, and Shenton line 1

Critical Pitfalls to Avoid

• Do not perform universal ultrasound screening—the AAP recommends selective screening only, as most mild abnormalities normalize spontaneously and overdiagnosis leads to unnecessary treatment 1, 2
• Do not ultrasound before 2 weeks of age unless there is frank dislocation, as physiologic hip laxity causes false positives 2
• Do not rely on radiographs before 4 months—they cannot adequately assess the cartilaginous structures 1
• Do not dismiss limited hip abduction in older infants—this becomes the most reliable sign after 3 months when Ortolani/Barlow lose sensitivity 1
• Recent evidence shows 41-58% of abnormal physical exams are false positives when correlated with ultrasound, supporting the role of confirmatory imaging before initiating treatment 1

When Expertise Matters

The sensitivity and specificity of clinical examination depend heavily on examiner expertise 1. When physical findings are equivocal or the examiner is uncertain, ultrasound at 4-6 weeks provides objective confirmation and prevents both overtreatment and missed diagnoses 1.

Natural History Context

Understanding that 60-80% of clinically detected abnormalities and >90% of ultrasound abnormalities resolve spontaneously justifies the selective screening approach and delayed imaging at 4-6 weeks rather than immediate newborn screening 1, 2. However, untreated true dysplasia leads to early degenerative joint disease and impaired function, making accurate diagnosis essential 1.