CORRELATION BETWEEN ULTRASOUND AND X-RAY- IMAGING

For examination of the infant hip we cannot do without the use of an i maging method. The interpretation of ultrasound and X-ray studies does not always lead to uniform results. To clear up the so far unknown re lationship between ultrasound and X-ray studies, sonomorphologic and r adiomorphologic examinations were performed on 14 hip joints of childr en between 36 weeks and 12 1/2, months of age. A discrepancy between t he 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 t he ventral or dorsal section of the acetabulum in correct projection o f the X-ray image. The evaluation of the ultrasound image is then base d on a bony shape differing from the one on the X-ray image. If the ra diologic contour line of the acetabulum is determined by the mid-porti on of the acetabulum, the angle of the acetabulum in the X-ray image a nd the alpha angle in the ultrasound image always add up to 90 degrees . This leads to the conclusion that a correspondence between ultrasoun d and X-ray findings only exists when the mid-portion of the acetabulu m defines the acetabular contour line in the Xray image. Generally, ho wever, 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 examina tion has a higher value regardless of its margin of error, which is in herent in any metric method, because the critical mid-portion of the a cetabulum can be judged with this procedure. We are of the opinion tha t the X-ray image is not decisive for therapy and prognostic assessmen t in these cases.