Ossification center of the infant hip: sonographic and radiographic correlation.

A new sonographic technique for evaluating the ossification center of the infant's hip allowed identification of the ossific nucleus before it could be visualized radiographically. With this technique, delay in ossification associated with hip pathology can also be recognized. Proper assessment of the size of the ossific nucleus requires scanning in orthogonal planes. Acoustic shadowing causes the growing ossification center to appear curved and may make the medial acetabulum and triradiate cartilage difficult to identify. Sonographic hip evaluation usually ceases to be reliable in children over 1 year old.