数字化X线摄影三线比值在诊断婴儿发育性髋关节脱位中的价值

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

目的：探讨数字化X线摄影（DR）三线比值在婴儿发育性髋关节脱位（DDH）诊断中的价值。方法回顾性分析2009年6月至2014年5月共146例6个月以下临床疑诊髋关节脱位婴儿的骨盆平片，正常髋关节36例、髋脱位110例，其中髋关节发育不良40例、髋关节脱位70例；正常髋关节134髋、脱位髋关节158髋，其中发育不良57髋、脱位101髋。2名放射科医师分别采用盲法以股骨近端干骺端中点（o点）为起点，分别至髋臼外上缘（a线）、Y型软骨中心（b线）、髋臼下缘（c线）做连线，测量3条线的长度，计算a/b、a/c、b/c的比值，采用ROC曲线探讨三线比值与髋关节脱位类型的关系。结果正常髋关节三线比值（a/b、a/c、b/c）均接近于1，发育不良时比值〉1，脱位时比值〈1。b/c值对诊断髋关节发育不良的敏感度、特异度较低，诊断正常髋关节及脱位髋关节的敏感度、特异度较高；a/b、a/c值对诊断各脱位类型的敏感度和特异度均较高。在诊断正常髋关节时，当a/b=0.985，a/c=0.980，b/c=0.990，对应ROC曲线下面积分别为0.667，0.625，0.700（P〈0.05），b/c临界水平值诊断价值最高。在诊断髋关节发育不良时，当a/b=1.060，a/c=1.045，对应ROC曲线下的面积为0.934、0.905（P〈0.05），a/b临界水平值诊断价值最高。在诊断髋关节脱位时，当a/b=0.960，a/c=0.965，b/c=0.970，对应ROC曲线下的面积为0.985、0.918、0.746（P〈0.05），a/b临界水平值诊断价值最高。结论 DR三线比值可为6个月以下婴儿DDH的早期诊断提供客观的参考依据。

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.