The aim of this study was to evaluate whether universal (all neonates) or selective (neonates belonging to the risk groups) ultrasound screening of the hips should be recommended at birth.

We carried out a prospective, randomised trial between 1988 and 1992, including all newborn infants at our hospital. A total of 15 529 infants was randomised to either clinical screening and ultrasound examination of all hips or clinical screening of all hips and ultrasound examination only of those at risk. The effect of the screening was assessed by the rate of late detection of congenital or developmental hip dysplasia in the two groups.

During follow-up of between six and 11 years, only one late-detected hip dysplasia was seen in the universal group, compared with five in the subjective group, representing a rate of 0.13 and 0.65 per 1000, respectively. The difference in late detection between the two groups was not statistically significant (p = 0.22).

When clinical screening is of high quality, as in our study, the effect of an additional ultrasound examination, measured as late-presenting hip dysplasia, is marginal. Under such circumstances, we consider that universal ultrasound screening is not necessary, but recommend selective ultrasound screening for neonates with abnormal or suspicious clinical findings and those with risk factors for hip dysplasia.

We have evaluated the effect of the use of ultrasound in determining the initiation of treatment in neonatal instability of the hip. A total of 99 newborn infants (1.5% of all live births) with neonatal hip instability did not have treatment from birth, but were re-examined at eight to 15 days. In the 31 who had persisting clinical instability and ultrasound abnormality, treatment was then started with a Frejka pillow. The hips in the remaining 68 infants showed spontaneous clinical stabilisation and improvement of the ultrasound findings. Treatment was therefore withheld. There was a marked trend towards normal development in mildly unstable hips, whereas no hips with severe instability did so spontaneously.

Further follow-up showed normal development in all the hips which had been treated, and in all except five of the 68 untreated infants. These five infants showed persistent hip dysplasia on both ultrasound and radiological examination at four to five months of age. Treatment with an abduction splint was then started and their hips developed normally.

Ultrasound is very useful in deciding on treatment if the examiners have adequate experience with the method. Its use substantially reduces the rate of treatment. Spontaneous resolution occurred in more than half of the unstable hips. Since five of the untreated infants developed hip dysplasia a strict follow-up is essential to identify and treat these cases.

We have followed the natural progress of newborn infants in whom ultrasound examination showed abnormalities in hips which appeared to be clinically normal. Over six years we saw 306 such children out of 9952 examined (31 per 1000 live births). The examination was repeated at two to three months and those who still showed an abnormality were followed up further.

At four to five months a standard radiograph was obtained, and treatment began if this and another ultrasound scan were both abnormal. At this stage, 291 infants had normal hips. In the 15 infants with abnormal hips there was no pronounced deterioration, none developed a frank dislocation, and all became normal after treatment in an abduction splint.

Newborn infants with abnormal and suspicious ultrasound findings who are normal on clinical examination do not need treatment from birth; most of these hips will settle spontaneously. Treatment can be postponed until the age of four to five months unless clinical instability develops or ultrasound shows dislocation. The criteria for treatment should be based on measurements by both ultrasound and radiography: both should show an abnormality before intervention is considered necessary.