What is the significance of hip exams in pediatrics and what are the differential diagnoses?

Significance of Hip Examination in Pediatrics and Differential Diagnoses

Hip examination in pediatrics is critically important as unrecognized and untreated developmental dysplasia of the hip (DDH) inevitably leads to early degenerative joint disease, with DDH causing up to one-third of all total hip arthroplasties in patients under 60 years of age. 1

Importance of Hip Examination

• Hip examination should be performed at every well-baby visit according to the recommended schedule (2-4 days for newborns discharged in <48 hours, 1 month, 2 months, 4 months, 6 months, 9 months, and 12 months) 1
• Early detection allows for typically non-invasive and effective therapy, while late presentation is a major negative prognostic factor requiring more complex treatment and surgical intervention 1
• Physical examination is the most important screening method, with selective ultrasound screening recommended for high-risk infants 1, 2

Key Physical Examination Techniques

For Infants Under 3 Months:

• Barlow Test: Examiner gently adducts the thigh and applies posterior pressure to attempt to dislocate an unstable hip; a positive test implies a dislocatable hip 1, 2
• Ortolani Test: Examiner abducts and gently lifts the flexed thigh while pushing the greater trochanter anteriorly; a "clunk" indicates reduction of a dislocated hip back into the acetabulum 1

For Infants Over 3 Months:

• Limited hip abduction becomes the most important finding as Ortolani and Barlow tests become less sensitive due to increased tightening of the hip capsule 1
• Other findings include asymmetric buttock creases and leg length discrepancy 1
• In walking children, look for a typical limp or toe-walking on the affected side 1

Differential Diagnoses

1. Developmental Dysplasia of the Hip (DDH)

   • Ranges from mild acetabular dysplasia to complete dislocation 1, 3
   • Risk factors include female gender (RR 2.5), breech positioning (RR 3.8), positive family history (RR 1.4), and infant swaddling 1, 2

2. Immature Hip (Graf Type IIa)

   • Normal developmental variant in infants <3 months with alpha angle 50°-59° 1, 2
   • Most resolve spontaneously without treatment 1, 2

3. Dysplastic Hip (Graf Type IIb-IV)

   • Type IIb: Similar to IIa but detected in children >3 months 1
   • Types IIc, IId, III, and IV: Progressively abnormal hips with frank subluxation in types III and IV 1

4. Avascular Necrosis of the Hip

   • Can occur as a complication of DDH treatment 1, 4
   • Risk factors include corticosteroid treatment, alcohol abuse, hemoglobinopathies, hyperlipidemia, and hypercoagulability states 4

5. Teratologic Dislocation

   • Associated with neuromuscular disorders, myelodysplasia, or arthrogryposis 1
   • Present at birth and typically more rigid than typical DDH 1

Imaging Recommendations

• Under 4 months: Ultrasound is the preferred imaging modality 1, 2, 5

  • American Academy of Pediatrics recommends selective ultrasound screening at 4-6 weeks for high-risk infants 2
  • Two main ultrasound techniques: static (Graf method) and dynamic (Harcke method) 1

• Over 4-6 months: Radiography becomes more reliable as ossification progresses 1, 2, 5

  • Acetabular index is the most commonly used measurement (normal is 30° in newborns, decreases with age) 1
  • Position of femoral head evaluated using Hilgenreiner and Perkin lines 1

Common Pitfalls to Avoid

• Performing ultrasound too early (before 2 weeks) can lead to overdiagnosis due to physiologic laxity 2
• Overtreatment of physiologically immature hips can lead to iatrogenic avascular necrosis 1, 2
• Relying solely on physical examination without appropriate imaging follow-up in high-risk infants 2
• Assuming normal physical examination findings exclude DDH, as late-onset hip dislocation can occur in approximately 1 in 5000 infants with normal newborn exams 6

Treatment Principles

• The general treatment principle is to obtain and maintain a concentric reduction of the femoral head in the acetabulum 3
• Treatment ranges from less-invasive bracing to more-invasive surgical interventions depending on age and complexity 3
• Early treatment of an unstable hip with a Pavlik harness or similar orthosis is effective, safe, and strongly advised 6