Open Access Research article

Reliability and reproducibility analysis of the Cobb angle and assessing sagittal plane by computer-assisted and manual measurement tools

Weifei Wu, Jie Liang, Yuanli Du*, Xiaoyi Tan, Xuanping Xiang, Wanhong Wang, Neng Ru and Jinbo Le

Author Affiliations

Department of Orthopedics, the People’s Hospital of Three Gorges University, the First People’s Hospital of Yichang, Yichang, China

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BMC Musculoskeletal Disorders 2014, 15:33  doi:10.1186/1471-2474-15-33

Published: 6 February 2014



Although many studies on reliability and reproducibility of measurement have been performed on coronal Cobb angle, few results about reliability and reproducibility are reported on sagittal alignment measurement including the pelvis. We usually use SurgimapSpine software to measure the Cobb angle in our studies; however, there are no reports till date on its reliability and reproducible measurements.


Sixty-eight standard standing posteroanterior whole-spine radiographs were reviewed. Three examiners carried out the measurements independently under the settings of manual measurement on X-ray radiographies and SurgimapSpine software on the computer. Parameters measured included pelvic incidence, sacral slope, pelvic tilt, Lumbar lordosis (LL), thoracic kyphosis, and coronal Cobb angle. SPSS 16.0 software was used for statistical analyses. The means, standard deviations, intraclass and interclass correlation coefficient (ICC), and 95% confidence intervals (CI) were calculated.


There was no notable difference between the two tools (P = 0.21) for the coronal Cobb angle. In the sagittal plane parameters, the ICC of intraobserver reliability for the manual measures varied from 0.65 (T2–T5 angle) to 0.95 (LL angle). Further, for SurgimapSpine tool, the ICC ranged from 0.75 to 0.98. No significant difference in intraobserver reliability was found between the two measurements (P > 0.05). As for the interobserver reliability, measurements with SurgimapSpine tool had better ICC (0.71 to 0.98 vs 0.59 to 0.96) and Pearson’s coefficient (0.76 to 0.99 vs 0.60 to 0.97). The reliability of SurgimapSpine measures was significantly higher in all parameters except for the coronal Cobb angle where the difference was not significant (P > 0.05).


Although the differences between the two methods are very small, the results of this study indicate that the SurgimapSpine measurement is an equivalent measuring tool to the traditional manual in coronal Cobb angle, but is advantageous in spino-pelvic measurement in T2-T5, PT, PI, SS, and LL.

SurgimapSpine software; Manual tool; Sagittal parameters measurement; Differences