Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2018 Sep 4;13(1):223.
doi: 10.1186/s13018-018-0928-5.

Measurement of scoliosis Cobb angle by end vertebra tilt angle method

Jing Wang  1 , Jin Zhang  1 , Rui Xu  2 , Tie Ge Chen  1 , Kai Sheng Zhou  1 , Hai Hong Zhang  3
Affiliations

Measurement of scoliosis Cobb angle by end vertebra tilt angle method

Jing Wang et al. J Orthop Surg Res. .

Abstract

Background: Scoliosis is a common deformity, and its severity is usually assessed by measuring the Cobb angle on the spinal X-ray film. The measurement of the Cobb angle is an important basis for selecting therapeutic methods and evaluating therapeutic effects. To measure and calculate the scoliosis Cobb angle by end vertebra tilt angle method (tilt angle method) and assess its accuracy and usability.

Methods: It is deduced that the Cobb angle is the sum of upper and lower end vertebra tilt angles through the law of plane geometry. The project included 32 patients with scoliosis who have received treatment in our hospital from June 2011 to July 2016, whose Cobb angles were measured at various segments (total 50). The measuring results of the tilt angle method and the classical method were compared, and the time spent for the measurement of the two groups was respectively recorded with an electronic stopwatch for comparison. The interference of line marking in imaging data pixel in the two groups was compared using Beyond Compare software.

Results: The measuring results through PACS (picture archiving and communication systems) were regarded as the reference standard. There was no statistical difference for measuring the Cobb angle between the PACS method, end vertebra tilt angle method, and classical method. The end vertebra tilt angle method takes less measuring time than the classical method. The measuring error between the classical method and the tilt angle method showed no statistical significance for the difference.

Conclusion: The scoliosis Cobb angle can be measured accurately and rapidly using the principle of the Cobb angle being equal to the sum of tilt angles of the upper and lower end vertebra, where in the film data of imaging will not be easily contaminated. Under special conditions, the average measuring error is ± 3°.

Keywords: Cobb angle; End vertebra; Scoliosis; Tilt angle.

PubMed Disclaimer

Conflict of interest statement

Ethics approval and consent to participate

“Ethical approval was obtained by Lanzhou University Second Hospital Medical Ethics Committee Review Form. Approval reference if relevant.” We had all necessary consent from any patients involved in the study, including consent to participate in the study where appropriate.

Consent for publication

Not applicable

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Measurement of Cobb angle by classical method
Fig. 2
Fig. 2
a, b, c Measuring process of the Cobb angle by the end vertebra tilt angle method. d Measurement of the upper end vertebra tilt angle. e Measurement of the lower end vertebra tilt angle. f The upper end vertebra tilt angle α = 41°, the lower end vertebra tilt angle β = 30°, and the Cobb angle = α + β = 71°
Fig. 3
Fig. 3
a, b Line marking of the classical method in a sketch map. c Line marking of the tilt angle method in a sketch map. d Line marking of the classical method in the imaging data. e Line marking of the tilt angle method in the imaging data. f Occupied pixel space marked by the classical method. g Occupied pixel space marked by the tilt angle method
Fig. 4
Fig. 4
a Scatter diagram of Cobb angles measured by the three methods; X-axis represents the case numbers of the Cobb angle; Y-axis represents the Cobb angle. b Error scatter diagram of Cobb angles measured by the tilt angle method and the classical method; X-axis represents the case numbers of the Cobb angle; Y-axis represents the error range
Fig. 5
Fig. 5
a Normally placed film. b Tilted placed film. c Red dotted line: the rectangular structure of the imaging data itself, and the ruler line (arrow) is vertical to the real horizontal plane
See this image and copyright information in PMC

References

    1. Cobb J. Outline for the study of scoliosis. Instr Course Lect. 1947;5:261–275.
    1. He J, Yan Z, Zhi Y, et al. The study of the reliability in Cobb measurement on PACS workstation. Zhongguo ji zhu ji sui za zhi. 2006;16(10):732–734.
    1. Sangole AP, Aubin CE, Labelle H, et al. Three-dimensional classification of thoracic scoliotic curves. Spine. 2009;34(1):91–99. doi: 10.1097/BRS.0b013e3181877bbb. - DOI - PubMed
    1. Morrison DG, Chan A, Hill D, et al. Correlation between Cobb angle, spinous process angle (SPA) and apical vertebrae rotation (AVR) on posteroanterior radiographs in adolescent idiopathic scoliosis (AIS) Euro Spine J. 2014;24(2):306–312. doi: 10.1007/s00586-014-3684-1. - DOI - PubMed
    1. Qiao J, Liu Z, Xu L, et al. Reliability analysis of a smartphone-aided measurement method for the Cobb angle of scoliosis. J Spinal Disord Tech. 2012;25(4):88–92. doi: 10.1097/BSD.0b013e3182463964. - DOI - PubMed