• Clinical science

Developmental dysplasia of the hip

Abstract

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

  • Family history
  • Breech presentation
  • Inadequate intrauterine space for the fetus; (e.g., oligohydramnios, first born child, twins, large birth weight)
  • Diseases associated with ligamentous laxity
  • Teratologic hip dislocations

References:[3]

Pathophysiology

Typical DDH

  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
    • The left hip is the more commonly affected
    • Development of contractures around the hip
    • Problems associated with leg length discrepancy (e.g., abnormal gait, scoliosis, lordosis)
    • Accelerated osteoarthritis of the hip

Teratologic hip dislocation

  • Hip dislocation occurs early in-utero (especially around the 12th week of gestation) → abnormal hip development in-utero
  • A pseudoacetabulum is present at birth; the femur is irreversibly dislocated.
  • Much higher risk of degenerative joint disease

References:[3]

Clinical features

Teratologic hip dislocation

  • Fixed irreducible dislocation at birth
  • Barlow and Ortolani signs are not present.
  • Manifestations of the underlying condition (e.g., meningomyelocele, arthrogryposis)

Typical DDH

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
  • Possibly Galeazzi sign
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, Galeazzi sign, 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°
    • Normal findings
      • A well defined acetabular roof, and a smooth, round femoral head
      • Alpha angle > 60°
      • Beta angle < 55°
      • The femoral head is bisected by a line (called baseline) drawn down from the ilium
    • Graf's classification
      • I (normally developed, fully mature hips): alpha angle > 60°
        • Ia: beta angle < 55°
        • Ib: beta angle > 55°
      • II (dysplasia)
        • IIa (physiologic immaturity): infants under 3 months with an alpha angle 50–59°
        • IIb (mild to moderate dysplasia): infants over 3 months with an alpha angle 50–59°
        • IIIc (critical zone dysplasia): alpha angle 43–49° and a beta angle < 77°
        • IIId (femoral head is about to decenter): alpha angle 43–49° and a beta angle > 77°
      • III (severe dysplasia or subluxation): alpha angle < 43° and a beta angle > 77°
      • IV (dislocation)
        • Alpha angle < 43° and a beta angle > 77°
        • The labrum is inverted and/or lies between the femoral head and acetabulum.
  • 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
  • Arthrogram: indicated following closed reduction to ensure successful reduction (see “Treatment” below)
  • Hip CT: imaging of choice to follow up patients with a hip spica (see “Treatment” below)
  • Hip MRI: not used in the diagnosis of DDH

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 (e.g., von Rosen harness) 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; alternatives include rigid harnesses (e.g., von Rosen harness)
  • 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
Type of treatment Indications Comments
Nonsurgical therapy Bracing
  • All infants < 6 months of age with a positive stability test
  • A rigid brace (e.g., von Rosen harness) is preferred over a nonrigid brace (e.g., Pavlik's harness, Frejka harness) There are no high-quality studies that compare the effectiveness of the most commonly used Pavlik harness, with alternative harnesses (e.g., the rigid von Rosen harness).
  • The harness maintains the hips in 90–100° of flexion and 50° of abduction.
  • The harness should be worn for 23 hours in a day for at least 6 weeks
  • The goal of treatment is to create a physiologic concentric reduction to promote normal bone modeling in the acetabulum and normal ossification of the femoral head (see “Pathophysiology” above)
  • Screening with ultrasonography or x-ray (depending on the age) is required every 3–4 weeks during bracing
  • If evidence of hip reduction is not seen on ultrasonography or x-ray by 3–4 weeks, the brace should be discontinued and closed reduction must be considered.
  • Contraindications to bracing
    • Teratologic hip dislocation
    • Infants older than 6 months
Closed reduction*
  • First-line therapy for infants 6–18 months
  • Failure of bracing
  • Closed reduction is performed under general anesthesia
  • Following closed reduction, arthrography must be performed to ensure successful reduction
Surgical therapy Open reduction*
  • First-line therapy for
    • Infants > 18 months
    • Teratologic hip dislocation
  • Failure of closed reduction
  • Capsulorrhaphy
  • Adductor tenotomy may also performed, especially in patients with severe contractures.
Type of approach for open reduction Advantage Disadvantage
Anterior incision (Smith-Peterson)
  • Versatile procedure that provides access to anterior and lateral structures, as well as permits pelvic osteotomy
  • Least risk of avascular necrosis of the femoral epiphysis (see “Complications” below)
Anteromedial incision (Weinstein-Ponseti)
  • Preferred in children less than 2 years
  • Pelvic and femoral osteotomies are not possible with this approach
  • Access to lateral structures is not possible
Medial incision (Ludloff approach)
  • Less blood loss
  • Easy to clear impediments to reduction of the femoral head (e.g., pulvinar fat)
  • Capsulorrhaphy is not possible
  • High risk of damage to the medial circumflex vessels → 10–15% risk of AVN (see “Complications” below)
Open reduction with femoral osteotomy*
  • Types of procedures
    • Intertrochanteric varus osteotomy with pediatric hip screw fixation
      • Aim: correct anteversion and/or coxa valgus deformities
      • More commonly performed in children < 3 years
    • Primary femoral shortening
      • Aim: decrease the tension produced on the blood vessels during open reduction and thus prevent avascular necrosis of the hip (see “Complications” below)
      • More commonly performed in children > 3 years
Open reduction with pelvic osteotomy*
  • Types of procedures
    • Redirectional pelvic osteotomies
      • Single innominate osteotomy (Salter)
      • Double innominate osteotomy (Sutherland or Hopf)
      • Procedures that free the acetabulum
    • Reshaping pelvic osteotomies
      • Acetabuloplasty (Pemberton)
      • Dega osteotomy
    • Salvage osteotomies
      • Chiari osteotomy
      • Slotted-shelf procedure (Staheli procedure)
Total hip arthroplasty
  • Older adolescents or adults with severe pain and/or limitation of range of motion in the hip as a result of severe osteoarthritis
  • Hip arthroplasty should only be performed once skeletal maturity is attained.
  • NSAIDS, physiotherapy, and modification of activity may be used in the interim period until skeletal maturity is attained.
*Following closed or open reduction, the hip and pelvis should be immobilized with a hip spica cast for about 3 months.


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
    • Possibly, bilateral hip dislocation

References:[2]