✅ Model Answer:
• Diagnosis: Developmental Dysplasia of the Hip (DDH) — asymmetric thigh folds, limited hip abduction on the left, normal inflammatory markers. No fever, no pain. Hip ultrasound (Graf) shows alpha angle <60° (dysplastic), beta angle >55° (subluxated/dislocated).
• Any other test: Hip ultrasound (Graf method) — alpha angle (normal >60°), beta angle (normal <55°). Pelvic X-ray (after 4-6 months for ossific nucleus — but ultrasound is preferred in infants <6 months).
• What to do next: Start Pavlik harness (for infants <6 months) — maintain hips in 90-100° flexion and neutral abduction. Full-time wear for 6 weeks, then wean. Follow-up ultrasound weekly.
• Follow-up plan: Monitor with ultrasound every 1-2 weeks to confirm concentric reduction. If no reduction after 3-4 weeks → consider closed reduction and spica cast. Long-term: monitor for residual acetabular dysplasia.

✅ Model Answer:
• DDH is a spectrum of hip disorders ranging from mild acetabular dysplasia to complete hip dislocation.
• Pathophysiology: The femoral head is not properly seated in the acetabulum → abnormal development of the hip joint.
• Spectrum:
- Dysplasia: Shallow acetabulum (femoral head is still in the joint but not well covered).
- Subluxation: Partial displacement of the femoral head from the acetabulum.
- Dislocation: Complete loss of contact between the femoral head and acetabulum.
• Incidence: 1-2 per 1000 live births (more common in females, breech presentation, positive family history).
• Risk factors:
- Breech presentation (especially frank breech)
- Female sex (4-5:1)
- Family history of DDH
- Firstborn (due to uterine constraint)
- Oligohydramnios
- Congenital torticollis, metatarsus adductus (associated conditions)

✅ Model Answer:
• Clinical features:
- Asymmetric thigh folds: Unequal number or depth of skin folds on the medial thighs.
- Limited hip abduction: The affected hip cannot be abducted to 70-80°.
- Galeazzi sign: The affected knee is lower than the contralateral when the hips are flexed (femoral shortening).
- Ortolani maneuver: A palpable "clunk" when the hip is reduced (abduction and forward pressure on the femoral head).
- Barlow maneuver: A palpable "clunk" when the hip is dislocated (adduction and backward pressure).
- Limb length discrepancy: Shortening of the affected limb.
- Limited range of motion: Hip stiffness.
- No fever, no pain.
- Waddling gait: In older children (after walking age).
- Trendelenburg sign: Pelvic drop when standing on the affected leg.

✅ Model Answer:
• Hip ultrasound (Graf method): The imaging modality of choice for infants <6 months (before the femoral head ossifies).
• Measurements:
- Alpha angle: Angle of the acetabular bony roof (normal >60°).
• >60° = normal
• 50-60° = mild dysplasia (type II)
• <50° = severe dysplasia (type III/IV)
- Beta angle: Angle of the acetabular cartilage (normal <55°).
• <55° = normal
• >55° = subluxation/dislocation
• Types:
- Type I: Normal (alpha >60°, beta <55°).
- Type II: Dysplastic (alpha 50-60°, beta <55°).
- Type III: Subluxated (alpha <50°, beta >55°).
- Type IV: Dislocated (alpha <50°, beta >55°).
• Advantages: No radiation, dynamic assessment of the hip.
• Disadvantages: Operator-dependent, requires experienced sonographer.

✅ Model Answer:
• Pavlik harness (for infants <6 months): The standard treatment for reducible DDH.
- Position: Hips in 90-100° flexion and neutral abduction (not forced abduction).
- Wear: Full-time (24 hours/day) for 6 weeks, then wean to part-time (12-16 hours/day) for another 6 weeks.
- Monitoring: Ultrasound every 1-2 weeks to ensure concentric reduction.
- Success rate: 85-95% if started early (<6 months).
• Failed harness: If reduction is not achieved after 3-4 weeks.
• Closed reduction + spica cast: For infants 6-18 months.
- Procedure: Reduction under general anesthesia → spica cast for 3-4 months.
- Timing: Usually done at 6-18 months.
• Open reduction + pelvic osteotomy: For children >18 months or failed closed reduction.
• Contralateral hip: Should be screened (bilateral in 20-40%).

✅ Model Answer:
• X-ray (AP pelvis): Used after 4-6 months of age (when the femoral head ossifies).
• Findings:
- Normal: Femoral head is centered in the acetabulum, Shenton's line is intact.
- DDH:
• Shenton's line: Disrupted (the femoral neck and superior pubic ramus do not form a continuous arc).
• Acetabular index: Increased (>30° in infants, >25° in older children).
• Femoral head: Displaced laterally and superiorly (subluxation/dislocation).
• Delayed ossification: Smaller ossific nucleus on the affected side.
• Centre-edge angle of Wiberg: <20° (in children >5 years) indicates dysplasia.
• Limitations: X-ray is less sensitive than ultrasound in infants <6 months; ultrasound is the preferred modality.

✅ Model Answer:
• Complications:
- Premature osteoarthritis: Most common long-term complication — due to abnormal joint mechanics.
- Leg length discrepancy: Shortening of the affected limb.
- Limp (Trendelenburg gait): Due to abductor weakness and hip instability.
- Pain: Hip pain in adolescence and adulthood.
- Decreased range of motion: Hip stiffness.
- Avascular necrosis (AVN): Of the femoral head (if treatment is delayed or reduction is forceful).
- Acetabular dysplasia: Residual shallow acetabulum (may require pelvic osteotomy later).
- Pathologic fracture: Weakening of the bone.
- Permanent disability: If untreated, can lead to severe functional impairment.
- Total hip replacement: May be needed in adulthood if severe osteoarthritis develops.

✅ Model Answer:
• Prognosis:
- Excellent: If diagnosed and treated early (<6 months) with Pavlik harness (85-95% success).
- Good: If treated between 6-18 months with closed reduction and spica cast.
- Guarded: If treated after 18 months or if there is residual dysplasia.
- Residual dysplasia: May require pelvic osteotomy later in childhood.
- Risk of osteoarthritis: Higher if residual dysplasia persists.
- Life expectancy: Normal.
• Long-term follow-up:
- Orthopedic: Follow-up X-rays every 6-12 months until skeletal maturity.
- Monitor for residual dysplasia: Acetabular index, centre-edge angle.
- Monitor for AVN: If treatment was delayed or forceful.
- Physical therapy: To maintain hip range of motion and strength.
- Activity modification: Avoid high-impact sports if residual dysplasia is present.
- Long-term: Risk of premature osteoarthritis — may require hip replacement in adulthood (40-60 years).