Paediatrics Series: DDH - From Screening to Treatment

Visual Element: An interactive "Age Slider". As the user slides from "Newborn" to "4 Years", the treatment algorithm and imaging modality (US -> X-ray) changes dynamically.

Developmental Dysplasia of the Hip (DDH) represents a spectrum of pathology ranging from mild acetabular dysplasia to frank dislocation. It is the most common orthopaedic condition in the newborn, and failure to diagnose it early leads to early onset osteoarthritis and significant disability in young adulthood.

The term "Developmental" replaced "Congenital" (CDH) to reflect that the condition can evolve after birth. A hip can be normal at birth and dysplastic at 6 months. This implies that surveillance must be ongoing.

Part 1: Etiology and Risk Factors

The "Package" Risk Factors are well known.

• The 4 F's: Female (80%), First-born (tight uterus), Feet-first (Breech), Family History.
• Associated Conditions: Torticollis (20% association), Metatarsus Adductus. (The "Molded Baby").
• Post-natal: Tight swaddling in extension/adduction (traditional in some cultures) increases risk 10-fold. Safe swaddling allows hips to flex and abduct.

Part 2: Screening and Diagnosis

The Clinical Exam (The Art)

• 0-3 Months: The hip is lax.
  • Barlow Test: Back (Posterior). Adduct and push back. Tests if the hip is dislocatable.
  • Ortolani Test: Out (Abduct). Abduct and lift anteriorly. Tests if a dislocated hip is reducible. You feel a "Clunk" (reduction), not a "Click" (ligament snap).
• > 3 Months: The hip becomes stiff (contracted).
  • Limited Abduction: The most sensitive sign. Asymmetry > 10 degrees is significant.
  • Galeazzi Sign: Apparent leg length discrepancy with knees flexed.

Ultrasound Screening (The Science)

Used until the ossific nucleus appears (approx. 4-6 months). The Graf Classification:

• Type I: Normal. Alpha > 60.
• Type IIa: Immature (Alpha 50-59, age < 12 weeks). Physiologic. Observe.
• Type IIb: Dysplastic (Alpha 50-59, age > 12 weeks). Treat.
• Type IIc: Critical / Endangered (Alpha 43-49). Treat.
• Type III: Dislocated (Alpha < 43).
• Type IV: Dislocated + Distorted Labrum.

X-Ray Measurements

Once the femoral head ossifies, plain films are the gold standard.

• Hilgenreiner's Line: Horizontal line through triradiate cartilage.
• Perkin's Line: Vertical line from lateral acetabular edge. The head should be in the Infero-Medial quadrant.
• Acetabular Index (AI): The slope of the roof. Should be < 30 degrees at birth, < 20 degrees by age 2.
• Shenton's Line: Continuous arc from femoral neck to obturator foramen. A break implies subluxation.

Part 3: Treatment Algorithm by Age

0 - 6 Months: The Pavlik Harness

The gold standard for reducible hips.

• Mechanism: Holds hip in Flexion (100 deg) and Abduction (45 deg). This directs the femoral head into the acetabulum, stimulating concentric development.
• Protocol: Worn 23 hours/day. Weekly US checks.
• Success: 90-95% for Graf II/III. Lower for Type IV (Frank dislocation).
• Complications:
  • Femoral Nerve Palsy: Too much flexion. Baby stops kicking. Adjust harness immediately.
  • AVN: Too much abduction. Tamponades medial circumflex vessels.
  • Pavlik Disease: Erosion of posterior acetabulum if hip remains dislocated in harness.

6 - 18 Months: Closed vs. Open Reduction

The Pavlik is no longer effective (child is too big/strong).

• Closed Reduction: EUA + Arthrogram. If stable in "Safe Zone" -> Spica Cast.
• Open Reduction: If closed reduction fails (obstruction to reduction).
  • Obstructions (LIMBUS): Ligamentum Teres (hypertrophied), Inverted Limbus (Labrum), Muscle (Psoas tight), Bone (Acetabulum), Under (Transverse Ligament), Soft tissue (Pulvinar fat).
  • Approach: Medial (Ludloff) or Anterior (Smith-Peterson).

18 Months - 4 Years: Osteotomies

Simple reduction is rarely enough. The acetabulum is dysplastic and needs reshaping.

• Femoral Osteotomy: VRO (Varus Derotation Osteotomy). Shortening the femur decompresses the hip (lowers AVN risk) and correcting excessive anteversion.
• Pelvic Osteotomies:
  • Salter: Redirectional. Cuts through ilium. Rotates acetabulum forward and down. Requires mobile symphysis (under age 6).
  • Pemberton: Pericapsular. Hinges on triradiate cartilage. Reduces acetabular volume (good for large capacity hips).
  • Dega: Similar to Pemberton but posterior cut differs. Used often in cerebral palsy.

> 4 Years / Adolescence: Salvage

• Triple Osteotomy: Cuts Ischium, Pubis, Ilium. Allows massive rotation.
• PAO (Ganz): Periacetabular Osteotomy. The gold standard for adolescent/adult dysplasia. Preserves posterior column (allows early weight bearing).

Part 4: Avascular Necrosis (AVN) - The Enemy

AVN is iatrogenic in DDH. It is caused by forceful reduction or extreme positions (extreme abduction in spica).

• Consequence: Growth arrest of the proximal femur -> Short leg, Coxa Breva, severe deformity.
• Prevention: "Petrie Casts" (abduction range), femoral shortening to avoid tension, checking safe zones.

Conclusion

DDH care is a marathon, not a sprint. A hip reduced at 6 months can still become dysplastic at age 5. Long-term surveillance until skeletal maturity is mandatory.

Radiology Cheatsheet

Download a PDF overlay for measuring Alpha angles and Acetabular Indices.