Skeletal Radiology

, Volume 36, Issue 8, pp 761–767 | Cite as

Radiographic measures of thoracic kyphosis in osteoporosis: Cobb and vertebral centroid angles

  • A. M. Briggs
  • T. V. Wrigley
  • E. A. Tully
  • P. E. Adams
  • A. M. Greig
  • K. L. BennellEmail author
Scientific Article



Several measures can quantify thoracic kyphosis from radiographs, yet their suitability for people with osteoporosis remains uncertain. The aim of this study was to examine the validity and reliability of the vertebral centroid and Cobb angles in people with osteoporosis.

Design and patients

Lateral radiographs of the thoracic spine were captured in 31 elderly women with osteoporosis. Thoracic kyphosis was measured globally (T1–T12) and regionally (T4–T9) using Cobb and vertebral centroid angles. Multisegmental curvature was also measured by fitting polynomial functions to the thoracic curvature profile. Canonical and Pearson correlations were used to examine correspondence; agreement between measures was examined with linear regression.


Moderate to high intra- and inter-rater reliability was achieved (SEM = 0.9–4.0°). Concurrent validity of the simple measures was established against multisegmental curvature (r = 0.88–0.98). Strong association was observed between the Cobb and centroid angles globally (r = 0.84) and regionally (r = 0.83). Correspondence between measures was moderate for the Cobb method r = 0.72), yet stronger for the centroid method (r = 0.80). The Cobb angle was 20% greater for regional measures due to the influence of endplate tilt.


Regional Cobb and centroid angles are valid and reliable measures of thoracic kyphosis in people with osteoporosis. However, the Cobb angle is biased by endplate tilt, suggesting that the centroid angle is more appropriate for this population.


Kyphosis Measurement Radiograph Cobb angle Vertebral centroid Osteoporosis 



The authors gratefully acknowledge the assistance of Professor Jaap van Dieën for comments on multi-segment curvature analysis, Professor Sing Kai Lo for providing statistical advice, and the Medical Imaging Department, St Vincent’s Hospital, Melbourne. Funding was provided by the Physiotherapy Research Foundation (Australia), grant 013/05.


  1. 1.
    Kado DM, Christianson L, Palermo L, Smith-Bindman R, Cummings SR, Greendale GA. Comparing a supine radiologic versus standing clinical measurement of kyphosis in older women: the fracture intervention trial. Spine 2006; 31 4: 463–467.PubMedCrossRefGoogle Scholar
  2. 2.
    Arnold CM, Beatty B, Harrison EL, Olszynski W. The reliability of five clinical postural alignment measures for women with osteoporosis. Physiother Can 2000; 52 4: 286–294.Google Scholar
  3. 3.
    Carman DL, Browne RH, Birch JG. Measurement of scoliosis and kyphosis radiographs. Intraobserver and interobserver variation. J Bone Joint Surg Am Vol 1990; 72 3: 328–333.Google Scholar
  4. 4.
    Stotts AK, Smith JT, Santora SD, Roach JW, D’Astous JL. Measurement of spinal kyphosis: implications for the management of Scheuermann’s kyphosis. Spine 2002; 27 19: 2143–2146.PubMedCrossRefGoogle Scholar
  5. 5.
    Harrison DE, Cailliet R, Harrison DD, Janik TJ, Holland B. Reliability of centroid, Cobb, and Harrison posterior tangent methods: which to choose for analysis of thoracic kyphosis. Spine 2001; 26 11: E227–E234.PubMedCrossRefGoogle Scholar
  6. 6.
    Harrison DE, Harrison DD, Cailliet R, Janik TJ, Holland B. Radiographic analysis of lumbar lordosis: centroid, Cobb, TRALL, and Harrison posterior tangent methods. Spine 2001; 26 11: E235–E242.PubMedCrossRefGoogle Scholar
  7. 7.
    Chen Y. Vertebral centroid measurement of lumbar lordosis compared with the Cobb technique. Spine 1999; 24 17: 1786–1790.PubMedCrossRefGoogle Scholar
  8. 8.
    McAlister WH, Shackelford GD. Measurement of spinal curvatures. Radiol Clin North Am 1975; 13 1: 113–121.PubMedGoogle Scholar
  9. 9.
    Singer KP, Jones TJ, Breidahl PD. A comparison of radiographic and computer-assisted measurements of thoracic and thoracolumbar sagittal curvature. Skeletal Radiol 1990; 19 1: 21–26.PubMedCrossRefGoogle Scholar
  10. 10.
    Bernhardt M, Bridwell KH. Segmental analysis of the sagittal plane alignment of the normal thoracic and lumbar spines and thoracolumbar junction. Spine 1989; 14: 717–721.PubMedCrossRefGoogle Scholar
  11. 11.
    Singer KP, Edmondston SJ, Day RE, Breidahl WH. Computer-assisted curvature assessment and Cobb angle determination of the thoracic kyphosis. An in vivo and in vitro comparison. Spine 1994; 19 12: 1381–1384.PubMedCrossRefGoogle Scholar
  12. 12.
    Goh S, Price RI, Leedman PJ, Singer KP. A comparison of three methods for measuring thoracic kyphosis: implications for clinical studies. Rheumatology 2000; 39 3: 310–315.PubMedCrossRefGoogle Scholar
  13. 13.
    Goh S, Price RI, Leedman PJ, Singer KP. The relative influence of vertebral body and intervertebral disc shape on thoracic kyphosis. Clin Biomech 1999; 14 7: 439–448.CrossRefGoogle Scholar
  14. 14.
    McCloskey EV, Spector TD, Eyres KS, et al. The assessment of vertebral deformity: a method for use in population studies and clinical trials. Osteoporos Int 1993; 3 3: 138–147.PubMedCrossRefGoogle Scholar
  15. 15.
    Fon GT, Pitt MJ, Thies AC. Thoracic kyphosis: range in normal subjects. Am J Roentgenol 1980; 134: 979–983.Google Scholar
  16. 16.
    Osman AAH, Bassiouni H, Koutri R, Nijs J, Geusens P, Dequeker J. Aging of the thoracic spine. Distinction between wedging in osteoarthritis and fracture in osteoporosis: a cross-sectional and longitudinal study. Bone 1994; 15 4: 437–442.CrossRefGoogle Scholar
  17. 17.
    Pradhan B, Bae HW, Kropf MA, Patel VV, Delamarter RB. Kyphoplasty reduction of osteoporotic vertebral compression fractures: correction of local kyphosis versus overall sagittal alignment. Spine 2006; 31 4: 435–441.PubMedCrossRefGoogle Scholar
  18. 18.
    Voutsinas SA, McEwan GD. Sagittal profiles of the spine. Clin Orthop Relat Res 1986; 210: 235–242.PubMedGoogle Scholar
  19. 19.
    De Smet AA, Robinson RG, Johnson BE, Lukert BP. Spinal compression fractures in osteoporotic women: patterns and relationship to hyperkyphosis. Radiology 1988; 166: 497–500.PubMedGoogle Scholar
  20. 20.
    Singer KP, Goh S. Anatomy of the thoracic spine. In: Giles LGF, Singer KP, editors. Clinical anatomy and management of thoracic spine pain. Oxford: Butterworth-Heinemann; 2000, p. 17–33.Google Scholar

Copyright information

© ISS 2007

Authors and Affiliations

  • A. M. Briggs
    • 1
    • 2
  • T. V. Wrigley
    • 1
  • E. A. Tully
    • 1
  • P. E. Adams
    • 1
  • A. M. Greig
    • 1
    • 2
  • K. L. Bennell
    • 1
    Email author
  1. 1.Centre for Health, Exercise and Sports Medicine, School of PhysiotherapyUniversity of MelbourneVictoriaAustralia
  2. 2.Department of Medicine, Royal Melbourne HospitalUniversity of MelbourneVictoriaAustralia

Personalised recommendations