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Developmental Dysplasia of Hip (DDH)

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  • Static vs. Dynamic Exam
    • Dynamic exam reveals subluxation during ROM
  • Applications
    • visual confirmation/quantification of disease in children with abnormal physical exams
    • monitoring efficacy of Pavlik harness treatment (every 7-10 days)
    • routine screening
      • used commonly in Europe
      • not cost effective
  • Morphological assessment
    • alpha angle - quantifies slope of superior aspect of acetabulum
      • 0-12 wks: >50 degrees is normal
      • 6-12 wks: > 60 degrees is normal
    • beta angle - quantifies cartilaginous aspect of acetabulum; not extremely useful
    • normal coverage: ~50%

Image Added

Radiography:

  • Plain radiographs should be used to confirm diagnosis at 4-6 weeks of age
  • proximal femoral ossific center appears at 4-7 months
  • radiographic lines
    • Hilgenreiner's line
    • Perkin's line
      • medial metaphyseal beak and secondary ossification center should be located in inferior, medial quadrant of intersection of Perkin's line and Hilgenreiner's line
    • Acetabular Index
      • Useful in children 8 y/o or younger
    • Acetabular angle of Sharp
      • used after triradiate cartilage is closed
    • Shentons line - should be intact on all views in patients older than 3-4 years of age
    • Lateral center edge angle (of Wiberg)
      • useful in children 5 y/o and older
    • Anterior center edge angle (of Lequesne)
    • For adult radiographic measurements, see the Hip Dysplasia page
  • Other radiographic findings:
    • absence of teardrop
    • delayed appearance of femoral head ossification center or small ossification center
  • Look for accessory centers of ossification in the acetabulum as the patient ages. Present in as many as 60% of DDH hips. They  are likely stimulated by abnormal forces between the femoral head and acetabulum and contribure to the development of a more normal, deeper acetabulum.

    MRI
  • Need for anesthesia limits utility

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  • PavliK harness fails to reduce the hip in as many as 8% of cases
  • AVN occurs in as many as 2.4% of cases splinted in the safe zone
  • AVN incidence increases in open procedures with an incidence of 
    • 8% for antero-lateral approaches
    • 10% for inguinal approaches
    • 17% for the Ludloff (medial) approach 
    • 5% when shortening femoral osteotomy was combined with open reduction
  • Salter indicators of AVN
    • Failure of appearance of the ossific nucleus 1 year after reduction
    • Failure of growth of an existing nucleus 1 year after reduction
    • Broadening of femoral neck 1 year after reduction
    • Increased radiographic density of the femoral head followed by radiographic appearance of fragmentation
    • Residual deformity of head and neck when re-ossification is complete
      • Coxa vara
      • Coxa magna
      • Coxa plana 
      • Coxa breva (short broad femoral neck)
    • Pre-reduction traction and adductor tenotomy did not decrease the incidence of AVN 
      • Abduction into the frog position was the incriminating factor, causing compression of vessels of the trochanteric anastomosis and retinacular vessels
      • Long term growth defect occurred in 0.7%

References

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