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Developmental Dysplasia of the Hip

Congenital hip joint luxation (DDH)

  • Disorder in which the acetabular and femoral head are misaligned resulting in unstable hip – usually present at birth but sometimes can present later as the hip develops
  • The hip joint has 3 main ligaments – the ileofemoral, pubofemoral and ischiofemoral
    •  the main function is to articulate bones together and stabilise the hip joint when moving

Epidemiology

  • Most common congenital abnormality of skeletal development
  • More common in females
  • Most common in the left hip

Etiology/Risk factors

  • First born
  • Breech
  • Family history
  • Oligohydraminos
  • Macrosomia

Pathophysiology

  • Initial instability is due to the risk factors → leads to dysplasia → leads to subluxation and eventually dislocation
  • Chronic dislocation leads to
    • Further difficulty in reduction – thickening of Pulvinar thickening of ligamentum teres; hypertrophy of the transverse acetabular ligament
    • Anatomic changes – flattening of the femoral head, femoral anteversion, decreased concavity of acetabular roof

Spectrum of disease

  • Dysplasia – shallow or underdeveloped acetabulum
  • Subluxation – displaced joint, with some contact between articulating surfaces
  • Dislocation – completely displaced joint, with no contact between articulating surfaces
  • Teratologic hip – dislocated in utero, presents with Pseudoacetabulum
  • Adolescent dysplasia – stable and reduced but dysplastic 

Classification

  • Subluxable – Barlow-suggestive
  • Dislocatable – Barlow-positive
  • Dislocated – Ortolani-positive when reducible (early); Ortolani-negative when irreducible (late)

Clinical features

  • Gluteal fold asymmetry
  • Abduction range asymmetry

Physical exam

  • Under 3 months
    • Positive Barlow test – adduct hip and apply pressure to push back and dislocate the femur
      • Felt by a ‘click’ when femur exits the joint as it dislocates
    • Positive Ortolani test – abduct the hip and elevate the femur to reduce it back into the hip joint
      • Felt by a ‘click’ when femur enters the joint as it reduces
  • 3 months – 1 year
    • Limitation in hip abduction – most sensitive test
    • Discrepancy in leg length
    • Klisic test – middle finger placed over greater trochanter, index finger placed over ASIS
      • Normal – should point towards the umbilicus
      • Dislocated – points halfway between umbilicus and pubis
  • Over 1 year
    • Pelvic obliquity
    • Lumbar lordosis
    • Trendelenburg gait
    • Toe-walking

Imaging

X-ray – after 4-6 months when femoral head begins to ossify

  • Dislocation
    • 2 lines are drawn on the X-ray
      • Hilgenreiner’s line – across the triradiate cartilages of the acetabulae
      • Perkin’s line – perpendicular to H line, passes through lateral edge of the acetabular roof
    • Normal – femoral head should lie in the inferomedial quadrant of these two lines
  • Dysplasia
    • Acetabular Index – angle formed by H line and a line from a point on the lateral triradiate cartilage to a point on the lateral margin of acebulum
    • Normal – should be <25o
Utrasound
  • Alpha angle – angle between the bony roof of the acetabulum and the ilium
    • Should be >60o. Less than this indicates a shallow acetabulum
  • Beta angle – angle between the labrum and the ilium
    • Should be <55o

Treatment

  • Under 6 months – Pavlik harness : keeps the hip flexed and abducted; should be worn for 23 hours per day
  • 6 – 18 months – closed reduction and spica casting
  • Over 18 months – open reduction with femoral/pelvic osteotomy, followed by casting

Complications

  • Avascular necrosis of the femoral head
  • Femoral nerve palsy
  • Osteoarthritis
  • Asymmetric gait
  • Decreased range of motion in hip joint
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