Ultrasound screening of the infant's hip: introduction of a new combined angle

This study evaluates the most widely used sonographic measurements for judging an infant's hip morphology. The alpha and beta angles of Graf, the bony coverage percentage of Morin and a new combined angle were analysed. This latter angle records the direction of the whole acetabulum (cartilagenous and bony) as one unit. One-hundred sonograms were examined independently by two observers to calculate the interobserver and intraobserver limits of agreement. The new combined angle proved to be the most reproducible measurement. Graf's alpha angle was the second most reliable measurement followed by the bone coverage percentage. The relationship between the combined angle and alpha angle was statistically significant with a correlation coefficient of 0.70 (P<0.001).