[Correlation between ultrasonography and roentgen imaging].

Abstract

For examination of the infant hip we cannot do without the use of an imaging method. The interpretation of ultrasound and X-ray studies does not always lead to uniform results. To clear up the so far unknown relationship between ultrasound and X-ray studies, sonomorphologic and radiomorphologic examinations were performed on 14 hip joints of children between 36 weeks and 12 1/2 months of age. A discrepancy between the X-ray and ultrasound image is always found when the contour line of the acetabulum does not correspond to the mid-portion but rather to the ventral or dorsal section of the acetabulum in correct projection of the X-ray image. The evaluation of the ultrasound image is then based on a bony shape differing from the one on the X-ray image. If the radiologic contour line of the acetabulum is determined by the mid-portion of the acetabulum, the angle of the acetabulum in the X-ray image and the alpha angle in the ultrasound image always add up to 90 degrees. This leads to the conclusion that a correspondence between ultrasound and X-ray findings only exists when the mid-portion of the acetabulum defines the acetabular contour line in the X-ray image. Generally, however, there is no constant relation between the X-ray summation image and the ultrasound image. The maximum error found by experiment is 8 degrees in the X-ray determination of the acetabular angle, 11 degrees in the ultrasound determination of the alpha angle and 28 degrees in the ultrasound determination of the beta angle. The ultrasound examination has a higher value regardless of its margin of error, which is inherent in any metric method, because the critical mid-portion of the acetabulum can be judged with this procedure. We are of the opinion that the X-ray image is not decisive for therapy and prognostic assessment in these cases.