Value of digital radiography in relationship between the proportion of three lines and the dislocation types of developmental dislocation of the hip in infants

Abstract

Objective To evaluate the value of digital radiography in relationship between the ratio of three lines and the dislocation types of developmental dislocation of the hip(DDH) in infants. Methods One hundred and forty six infants less than six months old with suspected DDH were retrospectively reviewed. One hundred and forty six infants (n=292 hips) included normal hips (n=36 cases), dysplasia (n=40 cases) and dislocation (n=70 cases). Three lines were measured from the midpoint of the femoral metaphysis to upper margin, lower margin and Y-shaped cartilage center of the acetabulum, respectively. The values of a/b, a/c and b/c were calculated. Then the relationship between the ratio of three lines and dislocation types were investigated by the receiver operating characteristic (ROC) curve. Results The values of a/b and a/c were 1 for normal hips, more than 1 for dysplasia, less than 1 for dislocation. The Se, Sp and YI of b/c value were much higher for normal hips and dislocation than dysplasia. The Se, Sp and YI of a/b and a/c value were very meaningful for all kinds of hips.The Se, Sp and YI of normal hips were maximal when a/b=0.985,a/c=0.980 and b/c=0.990. The areas under the curve (AUC) were 0.667, 0.625, 0.700, P<0.05. The diagnostic value of b/c was the best according to the AUC.The Se, Sp and YI of dysplasia were maximal when a/b was 1.060 and a/c was 1.045. The AUCs were 0.934, 0.905, P<0.05. The values of a/b and a/c were found to be statistically insignificant.The diagnostic value of a/b was the best according to the AUC.The Se, Sp and YI of dislocation were maximal when a/b was 0.960, a/c was 0.965 and b/c was 0.970. The AUCs were 0.985, 0.918 and 0.746, P<0.05. The a/b value was the most excellent marker according to AUC. Conclusion The research on digital radiography in relationship between the proportion of three lines and the dislocation types provides a new method for infant DDH, especially infants less than six months old. Key words: Radiography; Hip dislocation; Infants