DIAGNOSIS

The neonate with DDH may reveal remarkable findings on clinical examination. Although the majority of the hips with a positive Barlow or Ortolani test reveal some form of DDH (high sensitivity), these tests are not positive in all patients with DDH (imperfect specificity). Clearly, factors such as the age of the patient and the experience of the examiner influence test performance. Therefore, the accuracy of these tests cannot be quantified by one single number. Limited hip abduction is another potential but unreliable clinical sign for DDH. In a sample of Dutch infants aged 3 to 10 months, the finding of unilateral limitation of abduction had an overall sensitivity for the diagnosis of DDH of 69%, a specificity of 54%, a positive predictive value of 43%, and a negative predictive value of 78%; 46% of infants without DDH exhibited definite limited abduction.⁴

In addition to the clinical examination, ultrasound can be used to evaluate the neonatal hip. The result of the ultrasound test may be consistent with the clinical findings, or it may be inconsistent and provide additional information. For instance, an Ortolani-positive hip will show dislocation on ultrasound (findings are consistent). However, a clinically stable and unremarkable hip may reveal a shallow acetabulum and reduced femoral head coverage on ultrasound, which is an abnormal sonographic finding. The management of such hips remains highly controversial because the significance of some sonographic findings is unclear.

Abnormalities of the neonatal hip can be grouped into clinical abnormalities (instability of the hip, dislocatability of the hip, limited unilateral abduction of the hip) and by sonographic abnormalities (sonographic instability, reduced femoral head coverage, shallow acetabulum). No standardized diagnostic criteria have been established, however, with which these abnormalities can be distinguished from forms of DDH that will not resolve spontaneously.³

Because abnormalities of the hip present at birth are modulated by ongoing growth and because resolution of less severe abnormalities (Barlow-positive hips) was reported in up to 95% of patients,^5,6 a relevant question is up to which age treatment can be delayed without altering outcomes.

NEONATAL HIP INSTABILITY

Gardiner and Dunn⁶ performed a randomized clinical trial to address this question.⁶ Abduction splinting was delayed until the age of 10 to 14 days, or commenced immediately in neonates (≤2 days old) with dislocatable hips (positive Barlow test). All infants in the “delay group” were monitored by means of ultrasound at the age of 2 weeks and were treated thereafter if hips had not improved. Treatment became necessary in 29% of all infants. The trial revealed similar outcomes for those who received immediate treatment at the age of 2 days or younger, and for those who received delayed treatment (if it was still indicated because the hip did not resolve spontaneously) at the age of 2 weeks.

Outcomes included sonographic and radiographic parameters at 6 and 12 months of age. The findings of this trial suggest that ultrasound can reduce the number of neonates with unstable hips treated with splinting by as much as 70%. The authors conclude that dislocatable hips at birth may be safely watched sonographically for 2 weeks before determining the need for treatment without altering the outcome.

Of interest, the authors distinguished between hips that were dislocatable (positive Barlow test) and those dislocated at birth (positive Ortolani test). The latter was not part of their trial because common practice is that such hips warrant immediate treatment.

Based on the findings of this trial,⁶ the U.K. Collaborative Hip Trial group⁷ wanted to establish whether it was safe not to splint hips that were clinically suspect but seemed normal on ultrasound surveillance. Their concern was that such a regimen might increase the numbers of children requiring late treatment for DDH. The primary outcome of the trial was radiographic hip appearance at the age of 2 years. Eligible were infants 0 to 6 weeks old who had been diagnosed with neonatal hip instability by a senior physician.

The experimental intervention was ultrasound of the hip at the age of 2 weeks or older; if ultrasound showed significant displacement or instability, splinting was initiated. The nonexperimental intervention was treatment based on clinical examination alone. In the latter group, it was at the treating clinicians’ discretion to splint hips early (as soon as they were seen for assessment at 0–6 weeks of life), or to monitor hips clinically up to 8 weeks of age. If by the age of 8 weeks the hip was still of concern on clinical evaluation, splinting was initiated.

This randomized trial clearly showed that the use of ultrasound for the diagnosis and treatment of DDH significantly reduced the number of abduction splinting. Fewer children in the ultrasound group received treatment in the first 2 years of life. In contrast, splinting was done much earlier when the diagnosis was based on clinical examination alone—81% had splints fitted within the first 2 weeks. This trial also demonstrated that the total mean costs per used resources were similar in both groups.

How can these results be compared with those of Gardiner and Dunn’s trial?⁶ Gardiner and Dunn studied babies with dislocatable hips on clinical examination (positive Barlow test) and randomized them into early treatment or ultrasound and observation for 2 weeks. Also, the U.K. Collaborative Hip Trial group⁷