Measurement of the Cobb angle by 3D ultrasound: a valuable additional method for the prenatal evaluation of congenital scoliosis

Background: This study aimed to measure the Cobb angle of the fetal spine using three-dimensional ultrasound (3D-US) and to assess the relationship between the Cobb angle and the prognosis of congenital scoliosis. Methods: From March 2015 to June 2019, 77 pregnant women whose fetuses had suspected spinal skeletal dysplasia consented to undergo three-dimensional ultrasound (3D-US) examinations, and 54 fetuses were selected for the analysis group. The study protocol was approved by the review board of the Institutional Ethics Committee for Fetal Medicine. 3D-US was used to show the structure of the fetal spine in 3 planes, and the Cobb angle was measured on the coronal plane. The diagnostic efficacy of 3D-US was compared to that of X-ray for 33 fetuses. Results: In the diagnosis of congenital scoliosis, the sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) of 3D-US were 91.7%, 90.0%, 90.7%, 88.0%, and 93.1%, respectively. The area under the receiver operating characteristic (ROC) curve with 3D-US was 0.908. The Spearman correlation coefficient between the Cobb angle measurement on an X-ray image and on the coronal plane image acquired by 3D-US was 0.84, which showed a significant correlation (P<0.05). Conclusions: 3D-US was successful in the diagnosis of congenital scoliosis. It is feasible to measure the Cobb angle on the coronal plane of the fetal spine by using 3D-US. The Cobb angle has the potential to become an auxiliary index for evaluating the prognosis of congenital scoliosis.