What physical exam tests and investigations should be done for a 5-month-old infant with asymmetrical hip creases to confirm developmental dysplasia of the hip (DDH)?

Physical Examination and Investigations for a 5-Month-Old with Asymmetrical Hip Creases

For a 5-month-old infant with asymmetrical hip creases, limitation of hip abduction test should be performed as the primary physical examination maneuver, followed by radiographic evaluation of the pelvis to confirm developmental dysplasia of the hip (DDH). 1, 2

Physical Examination Tests

Primary Physical Examination Tests (at 5 months of age):

• Limitation of hip abduction test: This is the most important clinical sign after 3 months of age 1, 2

  • Technique: Place the infant supine, flex both hips to 90°, and gently abduct each hip
  • Positive finding: Restricted abduction on the affected side compared to the normal side

• Assessment for leg length discrepancy (Galeazzi sign):

  • Technique: Place the infant supine with hips and knees flexed at 90°
  • Positive finding: Apparent shortening of the femur on the affected side, with one knee appearing lower than the other

• Examination for asymmetry:

  • Check for asymmetry of gluteal folds
  • Assess for thigh fold asymmetry (though this alone has limited clinical significance) 3

Note on Ortolani and Barlow Tests:

• These tests are less reliable in infants older than 3 months 1, 2
• By 5 months, the Ortolani and Barlow tests are unlikely to yield positive results due to adaptive changes and soft tissue contractures 1, 4

Imaging Investigations

Primary Imaging (at 5 months of age):

• Radiography of the pelvis: This is the recommended first-line imaging for infants older than 4 months 1, 2
  • Views to obtain:
    • Anteroposterior view with hips in neutral position
    • Frog-leg view (if the neutral view is abnormal)
    • Von Rosen view (legs at 45° angle, abducted, and internally rotated) may help accentuate a dislocated hip

Radiographic Assessment Should Include:

• Evaluation of the relationship between the femoral head ossific nucleus (if present) and acetabulum
• Assessment of the relationship between proximal femoral metaphysis and acetabulum
• Measurement of the acetabular index (though note there is significant measurement variability)
• Evaluation of acetabular development (look for vertical orientation of the acetabular roof)

Common Pitfalls and Caveats

• Asymmetric skin folds in the medial thigh alone are not reliable indicators of DDH in infants 4-12 months of age 3
• The ossific nucleus of the femoral head typically appears at around 4 months (range 2-8 months), which makes radiographic evaluation more reliable at 5 months 1
• Radiographic interpretation requires expertise, as positioning of the infant can influence assessment of acetabular development 1
• If radiographic findings are equivocal, referral to a pediatric orthopedic specialist is warranted 2

Risk Factor Assessment

While performing the examination, also assess for known risk factors for DDH:

• Female gender (2.5-5.36 times increased risk)
• History of breech positioning (3.8 times increased risk)
• Family history of DDH (1.4 times increased risk)
• Left hip (three times more frequently affected than right)
• History of swaddling with extended and adducted legs 2, 5

Early diagnosis and treatment are crucial, as untreated DDH can lead to early degenerative joint disease, premature osteoarthritis, abnormal gait, and decreased strength 2.