Developmental dysplasia of the hip

Epidemiology & Risk Factors

• Breech presentation (strongest RF; screened universally via US at 4-6 wks for females or males with clinical signs). c
• Female sex (~80% of cases due to maternal relaxin sensitivity).
• Family history of DDH.
• Firstborn status, oligohydramnios, associated deformities (torticollis, metatarsus adductus).
• Tight swaddling (excessive hip extension and adduction).
• Left hip > Right hip (due to intrauterine positioning against maternal sacrum).

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Clinical Features

• Infants (< 3 months):
  • Ortolani maneuver: Abduction + anterior translation $\to$ “clunk” of reduction (palpable relocation of dislocated femoral head).
  • Barlow maneuver: Adduction + posterior pressure $\to$ “clunk” of dislocation (dislocates unstable femoral head).
  • Note: Soft, high-pitched “clicks” without instability are benign ligamentous snaps.
• Older Infants (> 3–6 months): c
  • Limited hip abduction (< 60° while supine with hips flexed at 90°).
  • Galeazzi sign: Asymmetry in knee height with hips and knees flexed (femur appears shortened on the affected side).
  • Asymmetric skin folds (inguinal/thigh/gluteal; sensitive but non-specific).
• Toddlers / Walking Age:
  • Trendelenburg gait (unilateral DDH: pelvis tilts toward unaffected side during stance on affected leg).
  • Waddling gait (bilateral DDH).
  • Leg length discrepancy (LLD) and compensatory toe-walking.

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Diagnosis

• Initial / Screening:
  • Serial physical exams (Barlow & Ortolani) at every well-child visit until walking age.
• Imaging Modality Choice (Age-Dependent):
  • Age < 4–6 months: Hip Ultrasonography (cartilaginous unossified femoral head; dynamic stress testing reveals displacement and measured $\alpha$-angle $<60^{\circ }$).
    • Perform US at 4–6 weeks of life (not at birth) to avoid false positives from physiologic ligamentous laxity.
  • Age $\ge$ 4–6 months: AP and Frog-leg Pelvic Radiographs (ossification center of femoral head appears; assess acetabular index, Perkins line, and Shenton line disruption).
• Confirmatory:
  • Abnormal US ($\alpha$-angle $<60^{\circ }$ or coverage $<50\%$) or abnormal pelvic X-ray.

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Differential Diagnostics

• Transient Synovitis: Diff by acute-onset limp/hip pain following a viral URI in children aged 3–8 yrs; normal bony anatomy on imaging.
• Septic Arthritis: Diff by high fever, refusal to bear weight, elevated inflammatory markers (ESR/CRP), joint effusion, and synovial WBC $>50,000/\mu \text{L}$.
• Legg-Calvé-Perthes Disease (LCPD): Diff by idiopathic avascular necrosis in boys aged 4–10 yrs; presents with insidious limp and pain; X-ray shows femoral head collapse/flattening.
• Slipped Capital Femoral Epiphysis (SCFE): Diff by obese adolescent (10–16 yrs) with dull groin/thigh/knee pain and limited internal rotation; X-ray shows posterior displacement of femoral head (“ice cream slipping off cone”).
• Benign Hip Clicks: Diff by high-pitched, soft fascial snap with normal range of motion, negative Barlow/Ortolani maneuvers, and normal US.

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Management

• Age < 6 months:
  • First-line: Pavlik harness (dynamic splint maintaining hip in flexion and abduction for 6–12 weeks).
  • Monitor closely via weekly/bi-weekly US to confirm reduction and avoid complications.
• Age 6–18 months (or failed Pavlik):
  • Closed reduction under general anesthesia followed by hip Spica cast immobilization (typically for 3 months).
• Age > 18 months (or failed closed reduction):
  • Open surgical reduction $\pm$ pelvic/femoral osteotomy + postoperative Spica cast.

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Complications

• Avascular Necrosis (AVN) of the femoral head (most feared complication of Pavlik harness if placed in hyperabduction/hyperflexion or after aggressive reduction).
• Femoral nerve palsy (transient; caused by excessive hip flexion in harness).
• Early-onset hip osteoarthritis (secondary to residual acetabular dysplasia).
• Persistent limb length discrepancy and gait abnormalities.