What is the diagnosis and treatment approach for Developmental Dysplasia of the Hip (DDH)?

Developmental Dysplasia of the Hip (DDH): Diagnosis and Treatment Approach

Developmental dysplasia of the hip (DDH) requires early diagnosis and treatment with screening ultrasound at 6 weeks for high-risk infants, followed by appropriate interventions based on age and severity to prevent long-term complications such as premature osteoarthritis and mobility issues. 1

Definition and Epidemiology

DDH encompasses a spectrum of structural abnormalities involving the growing hip, ranging from mild acetabular dysplasia to complete dislocation. Key epidemiological facts include:

• Affects approximately 1.5 in 1,000 Caucasian Americans 2
• 4-8 times more common in females 2
• More common in firstborns, large infants, and those with family history of DDH 2
• 3 times more common in the left hip than the right hip 2
• Risk factors include breech presentation, female gender, family history, and oligohydramnios 1

Pathophysiology

The etiology of DDH is multifactorial:

• Abnormal ligament and hip capsule laxity in patients and families with DDH 2
• Mechanical factors such as reduced in-utero space and movement restriction 2
• Extreme hip flexion with knee extension (as in breech position) promotes femoral head dislocation 2
• Shortening and contracture of the iliopsoas muscle 2

Clinical Evaluation

All infants should undergo routine hip examination at well-baby visits during the first year of life:

• Ortolani test: Abducting and gently lifting the flexed thigh to detect if a dislocated hip reduces (positive "clunk" sound) 2
• Barlow test: Gently adducting the thigh to dislocate the femoral head posteriorly, then abducting to relocate it 2
• In children >3 months: Look for limitation of hip abduction and asymmetric thigh folds 2
• In walking children: Typical limp and toe-walking 2

Important: Normal physical examination does not rule out DDH, especially in high-risk infants 1

Diagnostic Imaging

Ultrasound Evaluation

• Optimal timing: After 2 weeks of age (as laxity often resolves spontaneously by then) 2
• Primary indication: Infants 4 weeks to 4 months with suspected DDH 1
• High-risk groups requiring ultrasound: Female infants born in breech position (mandatory), male infants born in breech position (optional) 1

Radiographic Evaluation

• Optimal timing: After 4 months of age when ossification centers of femoral heads are visible 2
• Primary indication: Infants 4-6 months of age 1
• Measurements: Hilgenreiner's line, Perkin's line, acetabular index, and Shenton's line 3

Classification (Graf System)

Based on ultrasound findings:

• Type I: Normal hips (α angle >60°) - require no treatment or follow-up 2
• Type IIa: Normal location but immature acetabulum (α angle 50-59°) in infants <3 months - require follow-up but no treatment 2
• Type IIb, IIc, IId: Require referral for treatment 2
• Type III and IV: Low and high displacement, respectively - require immediate treatment 2

Treatment Approach by Age

0-6 Months

• Observation: For mild instability, as 60-80% of cases identified on physical exam and >90% on ultrasound resolve spontaneously 1
• Pavlik harness: Primary treatment for unstable hips or significant dysplasia 1
  • Most effective when applied before 6 weeks
  • Success rate: 67-83%
  • Typical duration: 6-12 weeks
  • Monitor with ultrasound to confirm concentric hip reduction

6-18 Months

• Failed Pavlik harness: Consider rigid abduction orthosis 4
• Persistent DDH: Closed reduction and spica casting 4
• Monitor: Regular radiographic assessment to detect residual dysplasia 1

>18 Months

• Open reduction: Often necessary with possible femoral and/or pelvic osteotomies 4
• Femoral osteotomies: Indicated for excessive anteversion or valgus deformity 5
• Pelvic osteotomies: Primarily Salter osteotomy or Pemberton acetabuloplasty 5

Complications and Follow-up

Potential Complications

• Avascular necrosis of femoral head: Most serious complication of treatment 1
• Skin problems: Can occur with prolonged bracing 1
• Residual dysplasia: Can lead to early degenerative joint disease if undetected 4

Follow-up Protocol

• During treatment: Serial physical examinations and ultrasound to confirm concentric hip reduction 1
• Post-treatment: Regular radiographic assessment to monitor for residual dysplasia 1
• Long-term: Follow until skeletal maturity to detect asymptomatic residual hip dysplasia 4

Clinical Pitfalls to Avoid

• Delayed diagnosis: Children diagnosed after 6 months often require surgical correction 2
• Overtreatment: Treating normal hips can lead to iatrogenic avascular necrosis 2
• Inadequate follow-up: Even with successful initial treatment, residual dysplasia may develop 4
• Missed diagnosis: Normal physical examination does not preclude DDH development 2

Early diagnosis and appropriate treatment are critical for achieving optimal functional outcomes and preventing long-term complications such as abnormal gait, decreased strength, and premature osteoarthritis.