2 – Congenital dislocation of the hip

7. DDH (developmental dysplasia of the hip), etiology and pathology of

• DDH is the most common congenital musculoskeletal deformity
  • Affects approx. 2 out of 100 000 newborns in Europe
• Left hip is slightly more often affected than the right
  • Bilateral DDH is rare
• Etiology
  • Girls > boys
  • Breech position during delivery
    • Causes abnormal flexion of the hip
  • Firstborn children > later-born children
  • Family history
  • Oligohydramnios
• Pathology
  • The acetabulum is dysplastic and shallow
    • Normally the acetabulum contains 2/3 of the femoral head
    • In DDH the acetabulum contains less than 2/3
    • This increases the pressure on the surface of the hip
  • Subluxation / dislocation of the femoral head
    • Due to the shallow acetabulum
• Secondary changes
  • Occurs in untreated DDH -> secondary changes develop in the femoral head and acetabulum
  • These secondary changes make hip reduction more and more difficult
  • Bony changes
    • Delayed ossification of femoral head
    • Increased femoral antetorsion
      • = the shaft of the femur has a torsion, causing the femoral neck to rotate anteriorly
      • This increases the angle between the femoral neck and the condylar axis
    • Increased collodiaphyseal angle
    • Coxa valga
      • Due to increased collodiaphysal angle
  • Soft tissue
    • Loose capsule
    • Abnormal position of iliopsoas
      • The iliopsoas normally runs in front of the head of the femur
      • In DDH the tendon of the iliopsoas comes between the cavity of the acetabulum and the head of the femur
      • This makes it difficult to reduce the head of the femur through the narrowed opening

38. DDH, clinical and X-ray features of

• Clinical features
  • Limited motion of the limb
    • Especially abduction (adduction contracture)
  • Asymmetric skin folds on the thigh and gluteal region
  • Positive Barlow sign
    • A click is heard and felt when pressure is applied to dislocate the hip
    • This test shows that the hip can be dislocated, but is not currently dislocated
  • Positive Ortolani sign
    • A click is heard and felt when pressure is applied to reduce the hip
    • This test shows that the hip is reduceable and therefore currently dislocated
    • Positive Ortolani sign is the only definitive sign of DDH
  • Late
    • Limb length difference
    • Trendelenburg gait
• Diagnosis
  • Screening at birth, 3 weeks, 3 months, 6 months
    • Only in those with risk factors or if there is clinical suspicion
    • US or X-ray
  • Ultrasound
    • Used for infants < 4 months
    • Can detect clinically silent DDH
  • X-ray
    • Used for infants > 4 months
    • In AP and Lauenstein view
    • Shows acetabular dysplasia and hip location
    • Femoral head is above the Hilgenreiner line
    • Femoral head is lateral to the Perkin line

41. Conservative treatment of DDH

• If patient is < 6 months
• Baby must use a so-called Pavlik harness or an abduction splint, which secures the baby’s hips in a stable “frog-leg” position, allowing them to develop normally
  • Pavlik harness fixes the femoral head in the correct position
  • Over the time acetabulum will be deepened
  • Abnormal use of the Pavlik harness can cause osteonecrosis of the femoral head
• Pavlik harness rapidly becomes ineffective after 4 months of age -> abduction splint or plaster cast
• Has high success rate when used correctly

52. Surgical treatment of DDH (developmental dysplasia of the hip)

• If patient is already > 6 months old OR conservative treatment didn’t work
• The specific surgical treatment depends on the exact pathology, but it always involves open reduction of the joint
• Other procedures which may be necessary
  • Soft tissue procedures
    • Adductor and/or iliopsoas muscles may need operation because they adapt to the dislocated joint, causing contracture
  • Femur osteotomy (= varus de-rotational osteotomy)
    • Corrects collodiaphyseal angle and antetorsion
  • Pelvic osteotomy (= acetabulum-plasty)
    • Dega osteotomy
      • Done when socket is too wide and too shallow
    • Salter osteotomy
      • Done when the socket doesn’t sit properly on the femoral head
• Patient must wear spica cast afterwards