[Ultrasonography as initial imaging study can replace roentgen studies under certain circumstances in suspected congenital hip dysplasia].

Sonography of the infant hip is increasingly used in the investigation of congenital dysplasia of the hip (CDH). It tends to replace the radiological investigation, which was the common method up till now. In this study sonography and radiological investigation were compared for 255 patient (510 hips), who had been referred to the orthopaedic surgeon on the presumption of CDH. For the sonography the predictive value of a negative finding was 99% (95% CI: 99-100%). The predictive value of a positive finding was 87% (95% CI: 78-95%). Specificity was high: 98% (95% CI: 97-99%); sensitivity lower: 95% (95% CI: 90-100%). Our conclusion is that sonography can replace the radiological investigation if it shows a normal result, for an infant older than 3 months. Additional radiological investigation is necessary if the sonography is abnormal. For infants under 3 months of age the investigation should be repeated at the age of 3 months, at any rate in case of doubt.