Developmental Dysplasia of the Hip (DDH)

Definition

• Acetabular dysplasia - shallow acetabulum, head in joint but poorly covered
• Subluxation - partial displacement of the femoral head
• Dislocation - complete displacement of femoral head from the true acetabulum (reducible vs. irreducible)
• Teratologic dislocation - a separate entity, dislocated in utero, irreducible at birth, associated with neuromuscular conditions
• Campbell's Operative Orthopaedics 15th Ed 2026, p. 1403
• Bailey and Love's Short Practice of Surgery 28th Ed, p. 637

Incidence

Risk Factors / Aetiology

DDH associated with neuromuscular disease (e.g. arthrogryposis, cerebral palsy, myelomeningocele) is called teratologic dislocation - these hips are resistant to simpler treatments.

• Bailey and Love's, p. 637; Campbell's, p. 1404

Pathology / Secondary Changes

• Adductor musculature develops contracture - limiting abduction
• The acetabulum becomes shallower (true acetabulum fills with fibrofatty tissue - the pulvinar)
• The labrum becomes hypertrophied, inverted, and may obstruct reduction (limbus)
• The femoral head migrates superiorly and posteriorly; a false acetabulum (pseudoacetabulum) forms
• The femoral neck develops increased anteversion
• The joint capsule becomes hourglass-shaped

Clinical Features by Age

Neonate (0-3 months)

• Ortolani test (reduction test): Hip is dislocated. Flex hips and knees to 90°, stabilize pelvis, then abduct and lift the greater trochanter anteriorly - a palpable clunk of reduction = positive (reducible dislocation)
• Barlow test (provocation test): Hip is in joint. Adduct the flexed hip and apply posterior pressure - a palpable clunk of dislocation = positive (dislocatable hip)

Key: A clunk (palpable) is significant. A click (audible only) is nonspecific and not diagnostic.

Ortolani maneuver for DDH screening - Campbell's Operative Orthopaedics 15th Ed

Infant (3-18 months)

• Limited hip abduction (most reliable sign) - due to adductor contracture; compare sides
• Asymmetric thigh/inguinal skin folds (unreliable alone - normal infants can have asymmetry)
• Galeazzi sign (Allis sign): With hips and knees flexed to 90°, apparent femoral length discrepancy - positive for unilateral dislocation
• Limb shortening (telescoping may be present)

Walking Child (>12-18 months)

• Trendelenburg gait (lurching to affected side)
• Waddling gait in bilateral cases
• Lumbar lordosis - compensation for bilateral hip flexion contracture
• Unilateral toe-walking (apparent leg shortening)
• Limited abduction in flexion

Adolescent/Adult

• Exercise-induced hip/groin pain (sometimes referred to the knee)
• Progressive osteoarthritis if untreated - a major cause of OA in young adults

Diagnosis

Neonatal Clinical Screening

1. Is the hip dislocated?
2. If dislocated - is it reducible (Ortolani +) or not (Ortolani -)?
3. If not dislocated - is it dislocatable (Barlow +)?
4. If clinically normal - do risk factors demand ultrasound?

Ultrasound (USG) - Investigation of choice in infancy

• Modality of choice from birth up to ~9-12 months (before ossification of the femoral head)
• High-frequency linear probe; coronal view; infant in lateral decubitus, hip flexed and abducted
• Performed at 4-6 weeks for screening; selective use for "at-risk" infants
• Graf classification is standard:

Plain Radiograph - From 4-5 months onwards

AP pelvis radiograph with Hilgenreiner's and Perkins' lines - Bailey and Love's 28th Ed

• Hilgenreiner's line (H-line): Horizontal line through both triradiate cartilages
• Perkins' line (P-line): Vertical line through the lateral edge of the acetabulum, perpendicular to H-line
• Normal: femoral head (or metaphyseal beak) in the inner lower quadrant
• DDH: femoral head in the outer or upper quadrant
• Shenton's line: Disrupted in dislocation (normally a smooth arc from femoral neck to superior pubic ramus)
• Acetabular index: Normal ≤30° in newborns, ≤25° by 6 months; elevated = dysplasia
• IHDI grading: Refined classification of dislocation severity

CT/MRI

• Used post-operatively to assess concentric reduction (especially after spica casting)
• MRI is preferred to avoid radiation in children
• Useful if clinical concern persists after operative treatment

Treatment - Age-Based Algorithm

Birth to 6 weeks

0-6 months: Pavlik Harness

Pavlik harness - Bailey and Love's 28th Ed

• First-line treatment for DDH in infants up to 4-6 months
• Holds hip in flexion (~100°) and abduction (gentle); anterior strap controls flexion, posterior strap limits adduction and encourages abduction
• Worn full-time for 6-12 weeks, then weaned
• Success rate: ~85-90% for dislocatable hips; lower for true dislocation
• Complications: Avascular necrosis (AVN) of femoral head (avoid extreme flexion >110° and forced abduction), femoral nerve palsy (from excessive flexion)
• Harness treatment is unusual to succeed after 4-6 months

6-18 months: Closed or Open Reduction

1. Examination Under Anaesthesia (EUA) + Arthrogram + Closed Reduction
   • Check for obstacles to reduction (inverted labrum, pulvinar, hourglass capsule, tight psoas/adductors)
   • Adductor ± psoas tenotomy if blocking reduction
   • Achieve reduction, confirm with arthrogram
   • Hip spica cast (human position ~100° flexion, 45° abduction) for 3 months
2. Open Reduction (if closed fails or hip irreducible)
   • Medial approach (Ludloff): 6-24 months; direct access to medial structures blocking reduction; capsulorrhaphy not possible
   • Anterior approach (Smith-Petersen): from 9-12 months; allows simultaneous capsulorrhaphy and acetabular work
   • Followed by spica cast

18 months - 4 years: Open Reduction + Pelvic Osteotomy

• Pelvic (acetabular) osteotomies - redirect the acetabulum:
  • Salter osteotomy: Single innominate; redirects acetabulum anteriorly and laterally; up to ~4 years
  • Pemberton osteotomy: Incomplete periarticular; reduces acetabular volume; useful for large dysplastic acetabulum
  • Dega osteotomy: Posterolateral coverage; useful in neuromuscular DDH
  • Triple osteotomy (Tonnis, Steel, Ganz PAO): For older children and adults with open triradiate cartilage closed
• Femoral osteotomy (derotation + varus shortening): Reduces tension on femoral head, corrects anteversion; shortening reduces risk of AVN
• Combined pelvic + femoral osteotomy is often needed for older children

Adults / Young Adults with Residual Dysplasia

• Periacetabular Osteotomy (Bernese PAO): Redirects acetabulum in all planes; gold standard for symptomatic dysplasia in adults with preserved cartilage
• Total Hip Arthroplasty: For end-stage OA - technically challenging due to deficient bone stock and altered anatomy

Complications of Treatment

Complications of Untreated DDH

• Progressive acetabular dysplasia
• Formation of a false acetabulum (pseudoacetabulum)
• Premature hip osteoarthritis - a major cause of total hip replacement in adults under 50
• Leg length discrepancy
• Lumbar spondylosis (compensatory)

Screening Summary (AAOS Guidelines)

• Universal ultrasound screening: Not supported by moderate evidence
• Selective ultrasound (before 6 months): Recommended for breech presentation, family history, or clinical instability
• AP pelvic radiograph: Useful from 4 months onwards as an alternative to ultrasound
• Serial examinations: Until 6 months of age in all at-risk infants
• Campbell's Operative Orthopaedics 15th Ed 2026; Bailey and Love's Short Practice of Surgery 28th Ed; Grainger & Allison's Diagnostic Radiology; Schwartz's Principles of Surgery 11th Ed