• Clinical science

Developmental dysplasia of the hip

Summary

Developmental dysplasia of the hip (DDH) refers to hip instability, subluxation/dislocation of the femoral head, and/or acetabular dysplasia in a developing hip joint. The etiology is not yet fully understood but a breech presentation and family history of DDH are the most important risk factors. The clinical features depend on the age of the child. During the first 6 months, the child will be asymptomatic but the hip can be easily dislocated, and a clunk is felt during a hip examination. As the child grows older, contractures develop and abduction of the hip becomes limited. Deformities and leg length discrepancies also develop. A patient with DDH is at increased risk of accelerated osteoarthritis. Since DDH is a common congenital abnormality, all newborns must be screened by physical examination for DDH. Additional screening with imaging is recommended for children with a family history of DDH, a history of breech presentation, and/or clinical features of DDH. Ultrasonography is the imaging modality of choice for infants younger than 4 months, whereas x-rays are used for older children. The goal of treatment is to reduce and maintain the femoral head into the acetabulum as early as possible to allow the hip joint to develop normally. A rigid harness is used in children younger than 6 months. Children 6–18 months of age should be treated with closed reduction, while children older than 18 months should be treated with open reduction. Following either closed or open reduction, the hip should be immobilized in a hip spica cast. The prognosis is not good if treatment is initiated after 6 months.

Epidemiology

  • Incidence: most common congenital abnormality of skeletal development
    • Hip instability: 1 in 100 births
    • Dislocation: 1 in 1000 births
  • Sex: > (5:1)
  • Racial/regional background:
    • High incidence in Native American , Eastern European , and Sami populations
    • Low incidence in Chinese and black populations

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

The exact etiology remains unknown but a number of risk factors have been associated with DDH

References:[3]

Pathophysiology

  1. Children with DDH have varying degrees of hip instability, hip subluxation, and/or hip dislocation resulting in
  2. These secondary anatomic changes eventually prevent hip reduction → vicious cycle with persistent hip dislocation
    • Development of contractures around the hip
    • Problems associated with leg length discrepancy (e.g., abnormal gait, scoliosis, lordosis)
    • Accelerated osteoarthritis of the hip

References:[3]

Clinical features

Age Clinical features
< 6 months
  • Asymptomatic
  • Barlow sign: a palpable clunk caused by hip dislocation when the hip is flexed and adducted while applying downward pressure
  • Ortolani sign: a palpable clunk caused by hip reduction when the hip is flexed and abducted while applying upward pressure
6–18 months
> 18 months
  • Hip pain, and/or pain referred from the hip to the knee and/or anterior thigh
  • Possibly a hip deformity (e.g., coxa vara)
  • Waddling or Trendelenburg gait
  • Leg length discrepancy and toe walking to compensate for the difference in leg length
  • Possibly lumbar lordosis

Leg length discrepancy and/or asymmetrical gluteal folds will be absent in patients with bilateral DDH! Early diagnosis (e.g., in newborn screening) is essential, as prognosis worsens with increasing age!

References:[4]

Diagnostics

Screening

  • Physical examination must be performed at every well-baby visit for up to 6 months
  • Screening with imaging is recommended up to 6 months of age only if one or more of the following risk factors are present

Imaging

  • Hip ultrasound: imaging of choice in all infants younger than 4 months
    • Alpha angle < 60°
    • Beta angle > 55°
  • Hip x-ray (in AP and frog-leg lateral view): imaging of choice in infants older than 4 months
    • Findings of hip dislocation
      • Interrupted Shenton's line
      • The ossified nucleus of the femoral head lies at or above Hilgereiner's line
      • The ossified nucleus of the femoral head lies at or lateral to Perkin's line
    • Findings of acetabular dysplasia
      • Acetabular angle> 30° after 4 months
      • Center-edge angle < 19° in the age group 6–13 years, or < 25° in children older than 14 years

Ultrasound is the imaging technique of choice for diagnosis of DDH in infants less than 4 months while x-ray is the imaging modality of choice for infants older than 4 months

References:[5][4][6]

Treatment

  • < 6 months: a rigid brace that maintains the hips in 90–100° of flexion and 50° of abduction
  • < 6 months: Pavlik harness (most commonly used splinting device) that maintains the hips in 90–100° of flexion and 50° of abduction
  • 6–18 months; or failure of bracing: closed reduction followed by immobilization with a hip spica cast
  • > 18 months; or failure of closed reduction: surgical therapy (open reduction possibly with a pelvic/femoral osteotomy) followed by immobilization with a hip spica cast
  • Older adolescents or adults: total hip arthroplasty


References:[7]

Differential diagnoses

See differential diagnosis of pediatric hip pain

The differential diagnoses listed here are not exhaustive.

Complications

References:[7]

We list the most important complications. The selection is not exhaustive.

Prognosis

  • The outcomes of children with DDH who receive early treatment are generally good.
  • Factors associated with a poor prognosis
    • Late initiation of treatment (especially after 6 months)
    • Need for open reduction
    • Failure of a first-line treatment

References:[2]