DIAGNOSIS
A positive Ortolani or Barlow sign is diagnostic and warrants prompt orthopedic referral (Figure 5). If physical examination results are equivocal or inconclusive, follow-up at two weeks is recommended, with continued routine follow-up until walking is achieved. Patients with persistent equivocal findings at the two-week follow-up warrant ultrasound at age 3 to 4 weeks or orthopedic referral. Infants with significant risk factors, particularly breech presentation at birth, should also undergo imaging.18 AAP recommends ultrasound at age 6 weeks or radiograph after 4 months of age.1,18 AAOS recommends performing an imaging study before age 6 months when at least one of the following risk factors is present: breech presentation, positive family history of DDH, or previous clinical instability (moderate level of evidence).3
IMAGING
Ultrasound is the diagnostic test of choice for infants because radiographs have limited value until the femoral heads begin to ossify at age 4 to 6 months.18 Ultrasonography allows for visualization of the cartilaginous portion of the acetabulum and femoral head.1 Dynamic stressing is performed during ultrasound to assess the level of hip stability. A provider trained in ultrasound will measure the depth of the acetabulum and identify any potential laxity or instability of the hip joint. Accuracy of these findings is largely dependent on the experience and skill of the examiner.
Ultrasound evaluation is not recommended until after age 3 to 4 weeks. Earlier findings may include mild laxity and immature morphology of the acetabulum, which often resolve spontaneously.1,18 Use of ultrasound is currently recommended only to confirm diagnostic suspicion, based on clinical findings, or for infants with significant risk factors.18 Universal ultrasound screening in newborns is not recommended and would incur unnecessary costs.1,3,9 Plain radiographs are used after age 4 months to confirm a diagnosis of DDH or to assess for residual dysplasia.3,18
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