What is the optimal cutoff value of the axis-line-angle technique for evaluating trunk imbalance in coronal plane?
Accurately evaluating the extent of trunk imbalance in the coronal plane is significant for patients before and after treatment. We preliminarily practiced a new method, axis-line-angle technique (ALAT), for evaluating coronal trunk imbalance with excellent intra-observer and interobserver reliability. Radiologists and surgeons were encouraged to use this method in clinical practice. However, the optimal cutoff value of the ALAT for determination of the extent of coronal trunk imbalance has not been calculated up to now.



The purpose of this study was to identify the cutoff value of the ALAT that best predicts a positive measurement point to assess coronal balance or imbalance.



A retrospective study at a university affiliated hospital was carried out.



A total of 130 patients with C7-central sacral vertical line (CSVL) >0 mm and aged 10-18 years were recruited in this study from September 2013 to December 2014.



Data were analyzed to determine the optimal cutoff value of the ALAT measurement.



The C7-CSVL and ALAT measurements were conducted respectively twice on plain film within a 2-week interval by two radiologists. The optimal cutoff value of the ALAT was analyzed via receiver operating characteristic (ROC) curve. Comparison variables were performed with chi-square test between the C7-CSVL and ALAT measurements for evaluating trunk imbalance. Kappa agreement coefficient method was used to test the intra-observer and interobserver agreement of C7-CSVL and ALAT.



The ROC curve area for the ALAT was 0.82 (95% confidence interval: 0.753-0.894, p<.001). The maximum Youden index was 0.51, and the corresponding cutoff point was 2.59°. No statistical difference was found between the C7-CSVL and ALAT measurements for evaluating trunk imbalance (p>.05). Intra-observer agreement values for the C7-CSVL measurements by observers 1 and 2 were 0.79 and 0.91 (p<.001), respectively, whereas intra-observer agreement values for the ALAT measurements were both 0.89 by observers 1 and 2 (p<.001). The interobserver agreement values for the first and second measurements with the C7-CSVL were 0.78 and 0.85 (p<.001), respectively, whereas the interobserver agreement values for the first and second measurements with the ALAT were 0.91 and 0.88 (p<.001), respectively.



The newly developed ALAT provided an acceptable optimal cutoff value for evaluating trunk imbalance in the coronal plane with a high level of intra-observer and interobserver agreement, which suggests that the ALAT is suitable for clinical use.
Department of Radiology, Children's Hospital, Zhejiang University School of Medicine, 3333 Binsheng Rd, 310052 Hangzhou, China.
Rui-Fang
RF
Zhang
Department of Radiology, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuanxi Rd, 325027 Wenzhou, China.
Yu-Chuan
YC
Fu
Department of Radiology, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuanxi Rd, 325027 Wenzhou, China.
Yi
Y
Lu
Department of Radiology, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuanxi Rd, 325027 Wenzhou, China.
Xiao-Xia
XX
Zhang
Department of Radiology, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuanxi Rd, 325027 Wenzhou, China.
Yu-Min
YM
Hu
Department of Radiology, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuanxi Rd, 325027 Wenzhou, China.
Yong-Jin
YJ
Zhou
Department of Spine Surgery, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuanxi Rd, 325027 Wenzhou, China.
Nai-Feng
NF
Tian
Department of Radiology, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuanxi Rd, 325027 Wenzhou, China.
Jia-Wei
JW
He
Department of Radiology, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuanxi Rd, 325027 Wenzhou, China. Electronic address: yanzhihanwz@163.com.
Zhi-Han
ZH
Yan
D000293:Adolescent; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D012372:ROC Curve; D013902:Radiography, Thoracic / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012600:Scoliosis / Q000000981:diagnostic imaging*; D060726:Torso / Q000000981:diagnostic imaging*
Central sacral vertical line; Coronal balance; Interobserver agreement; Kappa statistic; Radiography; Spine