Developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) encompasses a range of developmental hip abnormalities: hip instability, subluxation or dislocation of the femoral head, and acetabular dysplasia. The etiology is not fully understood, but breech presentation and family history are the most important risk factors. Infants < 3 months of age are typically asymptomatic; DDH is diagnosed on routine screening infant hip examination and, for infants with risk factors for DDH, imaging. As the infant grows, contractures develop, which limit hip abduction. Certain abnormal physical examination findings, i.e., hip instability, limited hip abduction after 4 weeks of age, and leg length discrepancy, are indicative of DDH (i.e., clinical DDH). Imaging should be ordered for individuals with risk factors for DDH, clinical DDH, or instability that has resolved. Imaging for DDH includes hip ultrasound for infants 4 weeks–6 months of age and hip x-ray for those ≥ 4 months of age. Children with clinical DDH and/or abnormal imaging should be referred to orthopedics for management. The goals of treatment are to reduce the femoral head into the acetabulum as early as possible and to ensure this positioning is maintained to allow normal development of the hip joint. An abduction brace is used for infants ≥ 6 months of age, while surgical repair is recommended for those > 6 months of age or if abduction bracing is unsuccessful. DDH due to improper swaddling may be prevented by healthy hip swaddling.

• Incidence: most common congenital abnormality of skeletal development ^[1]
  • Hip instability: 1 in 100 births
  • Dislocation: 1 in 1000 births
• Sex: : ♀ > ♂ (4–5:1) ^[2]
• Race/ethnicity ^[1]
  • High incidence in Native American, Eastern European, and Sami populations
  • Low incidence in Chinese and Black populations

Epidemiological data refers to the US, unless otherwise specified.

• The exact etiology of DDH remains unknown.
• Several risk factors have been identified: ^[2][3][4]
  • Family history
  • Breech presentation
  • History of tight swaddling of the lower extremities
  • A history of prior hip instability that has resolved (see “Diagnosis”)

There is mixed evidence on inadequate intrauterine space for the fetus (e.g., oligohydramnios, first-born child, twins, large birth weight) and the associated risk for DDH. ^[4][5][6]

Children with DDH have varying degrees of abnormal hip growth such as hip instability, hip subluxation, and/or hip dislocation, which result in: ^[7]

• Hypertrophy of pulvinar fat in the acetabulum, transverse acetabular ligament, and/or ligamentum teres
• Acetabular dysplasia

Signs and symptoms ^[3][6][8]

• Typically asymptomatic in infants < 3 months of age ^[3][4]
• Difficulty opening the hips (e.g., when changing diapers), typically after 3 months of age
• Uneven leg length; and, if ambulatory, a compensatory gait; (e.g., limp, unilateral toe walking) ^[3][9][10]
• Verbal children and adults may indicate hip, knee, or anterior thigh pain.
• Adults may report clinical features of hip osteoarthritis. ^[9][11]

Physical examination ^[3][6]

• Asymmetrical gluteal folds, inguinal folds, and/or thigh folds (may be a normal finding)
• Hip instability: frankly dislocated hip or positive instability maneuvers for DDH
• Limited or asymmetric hip abduction, possibly with contractures ^[3]
• Leg length discrepancy, which can cause functional scoliosis ^[12]
  • Positive Galeazzi sign: unequal knee height when lying supine with hips and knees flexed
  • Unequal leg lengths on measurement
• Signs of bilateral DDH, which can manifest with: ^[10]
  • No asymmetrical skin folds, unequal leg lengths, and/or Galeazzi sign ^[12]
  • Abnormal Klisic test bilaterally ^[13]
  • Increased lumbar lordosis
  • Waddling gait

In bilateral DDH, asymmetrical skin folds, Galeazzi sign, and/or uneven leg lengths may be absent. ^[12]

The left hip is more commonly affected by DDH than the right hip; left occiput anterior positioning in utero may limit fetal abduction of the left hip. ^[4]

• Modalities ^[3][6]
  • Infant hip physical examination
    • Technique: visual inspection, DDH instability maneuvers, hip range of motion, and Galeazzi test to assess for clinical features of DDH
    • Timing: at each well-child visit through 6–9 months of age
  • Imaging: Obtain imaging for DDH for infants with risk factors for DDH.
    • Breech presentation: Obtain a hip ultrasound at 6 weeks and a hip x-ray at 6 months. ^[6]
    • Other risk factors: Obtain age-appropriate imaging for DDH once before 6 months of age (ideally at 4–6 weeks of age). ^[3][6][14]
• If abnormalities are detected: Proceed to “Diagnosis” and “Treatment.”

While some countries perform universal hip ultrasound screening for DDH, US guidelines recommend universal infant hip physical examination and, in infants with risk factors for DDH, selective imaging. ^[14]

Approach ^[3][6][14]

• Most cases of DDH are detected with screening (i.e., infant hip examination and/or risk-based imaging).
• Obtain diagnostic imaging at 4–6 weeks of age (or at presentation if older) in all children with ≥ 1 of the following: clinical DDH.
  • Hip instability: frankly dislocated hip, positive instability maneuvers for DDH (even if resolved)
  • Limited or asymmetric abduction after 4 weeks of age
  • Leg length discrepancy (e.g., positive Galeazzi sign)
• Consider imaging for patients with equivocal findings and/or if the caregiver is concerned.

Individuals with clinical DDH can be referred to orthopedics before imaging is performed. ^[3][6]

Instability maneuvers for DDH ^[3][6]

The following provocative tests are recommended in infants ≤ 6 months of age; sensitivity decreases after 3 months of age. Positive findings indicate hip instability. ^[3]

• Ortolani test: the most important physical examination to detect DDH in newborns ^[3]
  • Method: The hips and knees are flexed and abducted while applying anterior pressure to the back of the femoral trochanter.
  • Positive finding: palpable anterior movement or clunk as a dislocated hip reduces into the hip socket
• Barlow test (controversial) ^[3]
  • Method: The hips and knees are gently flexed and adducted; do not apply posterior pressure.
  • Positive finding: palpable posterior movement or clunk as a reduced hip subluxes or dislocates out of the hip socket

Remember to Open (Ortolani) the hips and bring them Back (Barlow) together.

High-pitched hip clicks do not indicate hip instability and may result from normal ligamentous laxity in young infants. ^[3]

Imaging for DDH ^[3][4][14]

• Bilateral ultrasound hip (static and dynamic)
  • Age: 4 weeks–6 months ^[3][4]
  • Findings
    • Frank dislocation
    • Alpha angle < 60° ^[4]
    • Roundness of the bony acetabular promontory
• Bilateral hip x-ray (AP and/or frog-leg)
  • Age: ≥ 4 months (after cartilage begins to ossify) ^[3][4]
  • Findings
    • Frank dislocation
    • Abnormal acetabular angle (i.e., increased acetabular index for age)
    • Reduced acetabular coverage of the femoral head (i.e., decreased center-edge angle)
    • Early-onset osteoarthritis in adults ^[15]
  • Radiological DDH classifications are often reported and are used to grade severity. ^[16][17]

Between 4 and 6 months of age, either a hip ultrasound or hip x-ray may be performed. ^[4][6][14]

Approach ^[3][6]

• Refer to orthopedics for clinical DDH or if there are abnormal findings on imaging.
• For children < 4 weeks of age with isolated Barlow sign, consider re-examination in 4 weeks with referral if persistent. ^[3][18]
• Treatment is determined by a pediatric orthopedic specialist and is based on patient age and severity.
  • Minor abnormalities on imaging with normal physical examination: Observation may be considered.
  • All other patients: Intervention is recommended.

Abduction bracing ^[3][8][18]

• Indication: < 6 months of age
• Mechanism: positional reduction of the affected femoral head by keeping the hips in flexed abduction ^[19]
• Options: : static rigid splint; (e.g., von Rosen harness; ) or dynamic soft splint (e.g., Pavlik harness) ^[14]
• Complications ^[3][14]
  • Hip disorders: hip dislocation, Pavlik harness disease, femoral epiphyseal avascular necrosis
  • Skin irritation
  • Femoral nerve palsy

Double diapering is not an effective treatment for DDH. ^[3]

Surgical repair ^[8][18]

• Indications: > 6 months of age or unsuccessful abduction bracing
• Mechanism: reduction of the affected femoral head and, in children, subsequent immobilization in a hip spica cast ^[8]
• Options
  • Infants 6–11 months of age: closed reduction
  • Children 12–18 months of age: open reduction
  • Individuals > 18 months of age: open reduction ± pelvic and/or femoral osteotomy
  • Older adolescents or adults: total hip arthroplasty

See “Differential diagnosis of pediatric hip pain.”

The differential diagnoses listed here are not exhaustive.

• Residual acetabular dysplasia, subluxation, and/or redislocation despite treatment
• Early osteoarthritis in the hip joint
• Leg length discrepancy which may manifest with back pain, functional scoliosis, and/or knee pain
• Genu valgum

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

• The outcomes of children with DDH who receive early treatment are generally good. ^[7]
• The reappearance of a U shaped acetabular teardrop shadow (Köhler's shadow) after reduction is an indicator of good hip function.
• Factors associated with a poor prognosis ^[20]
  • Late initiation of treatment (especially after 6 months)
  • Need for open reduction
  • Failure of a first-line treatment
  • Possibly, bilateral hip dislocation

Healthy hip swaddling ^[21]

Improper swaddling can lead to DDH. If swaddling is used, ensure the following to encourage proper hip development:

• Hips and knees should be in slight flexion and abduction and able to move freely.
• Avoid forced or sustained hip extension and adduction.
• For information on safe sleep swaddling, see “SIDS.” ^[22]

Do not tightly swaddle the lower body; prolonged extension and adduction of the hips and knees can result in DDH. ^[21]