European Spine Journal

, Volume 27, Issue 3, pp 578–584 | Cite as

Normal variation in sagittal spinal alignment parameters in adult patients: an EOS study using serial imaging

  • Hwee Weng Dennis Hey
  • Kian Loong Melvin Tan
  • Vikaesh Moorthy
  • Eugene Tze-Chun Lau
  • Leok-Lim Lau
  • Gabriel Liu
  • Hee-Kit Wong
Original Article



To describe normal variations in sagittal spinal radiographic parameters over an interval period and establish physiological norms and guidelines for which these images should be interpreted.


Data were prospectively collected from a continuous series of adult patients with first-episode mild low back pain presenting to a single institution. The sagittal parameters of two serial radiographic images taken 6-months apart were obtained with the EOS® slot scanner. Measured parameters include CL, TK, TL, LL, PI, PT, SS, and end and apical vertebrae. Chi-squared test and Wilcoxon Signed Rank test were used to compare categorical and continuous variables, respectively.


Sixty patients with a total of 120 whole-body sagittal X-rays were analysed. Mean age was 52.1 years (SD 21.2). Mean interval between the first and second X-rays was 126.2 days (SD 47.2). Small variations (< 1°) occur for all except PT (1.2°), CL (1.2°), and SVA (2.9 cm). Pelvic tilt showed significant difference between two images (p = 0.035). Subgroup analysis based on the time interval between X-rays, and between the first and second X-rays, did not show significant differences. Consistent findings were found for end and apical vertebrae of the thoracic and lumbar spine between the first and second X-rays for sagittal curve shapes.


Radiographic sagittal parameters vary between serial images and reflect dynamism in spinal balancing. SVA and PT are predisposed to the widest variation. SVA has the largest variation between individuals of low pelvic tilt. Therefore, interpretation of these parameters should be patient specific and relies on trends rather than a one-time assessment.


EOS Low back pain Radiographic parameters Sagittal spinal alignment Serial imaging 



We would like to thank Darren Koh Zhi-Sheng and Jonathan Tan Jiong-Hao for their help in applying for ethics approval for this study.

Compliance with ethical standards

Conflict of interest



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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.University Orthopaedics, Hand and Reconstructive Microsurgery (UOHC)National University Health SystemSingaporeSingapore
  2. 2.Yong Loo Lin School of MedicineNational University of SingaporeSingaporeSingapore

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