Ultrasonography and radiography of the hip in infants.

Both hip joints in 156 children, aged 2 months to 2 years, were examined by ultrasonography (ultrasound) and radiography. Pathologic findings were based on an increased acetabular index, bony defects of the lateral acetabular rim, and lateral and/or proximal displacement of the proximal femur. Each hip was classified as normal, dysplasia, subluxation, or dislocation. The same diagnosis was reached by ultrasound and radiography in 303 of the 312 hips. The accordance was good in normal joints, in subluxation, and in dislocation. However in 7 of the 15 hips with radiographic dysplasia, ultrasound was normal. These patients were not treated, and spontaneous normalization or improvement occurred in all of them. One parameter only, the distance from the lateral margin of the ossification center of the femoral head to Perkins' line, was measured by both ultrasound and radiography; the correlation was high (r = 0.73). We recommend ultrasound as the primary imaging technique when congenital dislocation is suspected clinically.