Congenital / Developmental Dysplasia of the Hip (CDH / DDH)

Definition and Spectrum

• Dysplasia - morphologic change in acetabulum or proximal femur without loss of contact
• Subluxation - articular surfaces in contact but not concentrically aligned
• Dislocation - articular surfaces of acetabulum and proximal femur have no contact at all

A - Dysplastic hip with superior acetabular defect; B - Intermediate dislocation with false acetabulum; C - High dislocation with reactive bone on ilium (Campbell's Operative Orthopaedics 15th Ed)

Epidemiology and Risk Factors

• Clinical hip instability occurs in 1-2% of term infants; up to 15% have imaging findings
• Risk factors (additive):
  • Breech presentation (most important)
  • Female gender
  • Positive family history (most important alongside breech)
  • Incorrect lower extremity swaddling (forced hip extension/adduction)
  • First-born child, oligohydramnios

Pathoanatomy

Clinical Features and Diagnosis

Screening Tests

• Barlow test: Hip in 90° flexion + adduction; posterior lateral pressure applied. A clunk = femoral head dislocating out the back of the acetabulum.
  • Note: AAP (2016) recommends no posterior-directed force - the test has no proven predictive value for future dislocation and can itself cause instability if performed forcefully.
• Ortolani test: From similar starting position, hip is abducted with gentle anterior pressure on the greater trochanter. A clunk = femoral head reducing into the socket.
• "Hip clicks" (soft tissue snapping) are benign and must be distinguished from the pathological "hip clunk"

• Limited abduction - the most reliable sign
• Galeazzi sign - apparent limb length discrepancy due to proximal femoral migration (see image below)
• Asymmetric thigh/gluteal skin folds
• Trendelenburg gait or limp in older, walking children

Galeazzi sign: asymmetric knee levels indicate apparent femoral length discrepancy on the dislocated side (Rosen's Emergency Medicine)

Imaging

• Hilgenreiner's line - horizontal line through triradiate cartilages
• Perkin's line - vertical line through lateral edge of acetabulum
• Femoral head ossification center should be in the inferomedial quadrant
• Shenton's line - smooth arc along inferior femoral neck to superior obturator foramen; disrupted in dislocation
• Acetabular index - normally <30° at birth, <20° by 2 years

Crowe Classification (for surgical planning in adults/late DDH)

Treatment - Age-Based Algorithm

Newborn - 6 months: Pavlik Harness (First-Line)

• Holds hips in flexion and abduction, allowing gradual reduction and acetabular remodeling
• Success rate ~85% when initiated before 6 months
• Used for: dislocated, located but unstable, or dysplastic hips
• An isolated positive Barlow test up to 2 weeks will often stabilize spontaneously - can monitor for 4-6 additional weeks
• Because 96% of pathologic ultrasound findings resolve within first 6 weeks, treatment can be safely delayed to that time if the hip is stable

6 - 18 months: Closed/Open Reduction + Spica Cast

• If Pavlik fails or child is older than 6-8 months: closed reduction under anesthesia followed by spica cast immobilization
• Arthrogram performed at time of reduction to confirm concentric position
• Open reduction may be needed if closed reduction fails

> 18 months: Open Reduction ± Osteotomies

• Most children beyond 18 months require open reduction
• Combined with:
  • Innominate (Salter) osteotomy - redirects acetabulum anterolaterally (most common for ages 18 months - 6 years)
  • Pemberton osteotomy - acetabuloplasty for residual dysplasia
  • Femoral osteotomy - derotation/shortening as needed to reduce tension on vessels
  • Triple innominate osteotomy - for older children/young adults with open triradiate cartilage
  • Periacetabular osteotomy (Ganz PAO) - preferred for skeletally mature patients with retained cartilage space

Adult / Late Presentation: Total Hip Arthroplasty (THA)

• Acetabular component placed at true acetabulum (not false acetabulum)
• Very small cup may be needed (≤40 mm)
• Limb lengthening limited to 3-4 cm maximum (sciatic nerve risk)
• Femoral osteotomy often needed to correct anteversion, angular deformity, narrow canal
• Abductor muscles are poorly developed and may require extensive release

Complications

• Avascular necrosis (AVN) of femoral head - most feared complication; can occur from reduction (especially forceful) or from the untreated dislocation itself
• Residual acetabular dysplasia - may persist after successful reduction, requiring secondary procedures
• Re-dislocation - after closed/open reduction
• Sciatic nerve palsy - with aggressive lengthening or reduction of high dislocations
• Trendelenburg gait - from abductor weakness or coxa vara
• Early osteoarthritis - the inevitable endpoint of untreated or inadequately treated DDH

Long-term Consequences if Untreated

• Progressive osteoarthritis
• Chronic back pain (from compensatory lumbar scoliosis)
• Aseptic necrosis of femoral head
• Significant limb length discrepancy and gait abnormality

• Campbell's Operative Orthopaedics 15th Ed 2026, Chapter: Congenital and Developmental Dysplasia of the Hip
• Rosen's Emergency Medicine - Concepts and Clinical Practice, Chapter 170: Pediatric Hip Disorders
• Harriet Lane Handbook 23rd Ed, Chapter 26: Hip Disorders
• Recent evidence: Tirta et al. (2025) Meta-Analysis on DDH risk factors, PMID 39853978 | Shanaa et al. (2025) Hip Resurfacing in DDH, PMID 40680148