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Intra- and Interrater Reliability of Cobb Angle Measurements on the Plane of Maximum Curvature Using Ultrasound Imaging Method

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Abstract

Study Design

Retrospective reliability study.

Objectives

To investigate the intra- and interrater reliability of Cobb angle measurements on the plane of maximum curvature (PMC) using ultrasound (US) images on children with adolescent idiopathic scoliosis (AIS).

Summary of Background Data

Cobb angle measurement on posteroanterior (PA) radiographs is the gold standard to assess curve severity. However, the PA Cobb angle does not reflect the true three-dimensional deformity.

Methods

One hundred one children with AIS (87 F; 14 M) (age: 13.7 ± 1.7 years) were recruited and 157 curves were recorded by clinicians on radiographs. Three raters, R1, R2, and R3 with 0, 4, and 20+ years of experience, respectively, measured the PA Cobb, vertebral axial rotation (VAR), PMC Cobb, and PMC orientations on US images. The true PMC orientations were determined using 3D reconstructions on the PA and lateral EOS radiographs. The reliability of R1 measurements on PMC orientations were validated using intermethod (US vs. EOS measurements) with the intraclass correlation coefficients (ICCs). Inter- and intrarater reliabilities, standard error measurements, and Bland-Altman’s bias were used to report the PMC Cobb and VAR measurements.

Results

Intermethod, inter-, and intrarater ICC(2,1) values for all reliability assessments were greater than 0.9. The mean absolute differences and the standard error measurements for both PMC Cobb and VAR were less than 4° and 0.5°, respectively. The PMC orientation was strongly correlated (r2 = 0.88) between both measurement modalities. There appeared to be a positive association between the difference of PMC and PA Cobb when the PA Cobb and the maximum VAR were greater than 30° and 14°, respectively.

Conclusion

The PMC Cobb and VAR can be measured reliably on US images. Future studies should validate the PMC Cobb angle and to include a wider Cobb angle range on participants.

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Authors and Affiliations

  1. Department of Surgery, University of Alberta, 116 St. and 85 Ave., Edmonton, Alberta, T6G 2R3, Canada

    Suzana Trac, Rui Zheng PhD, Doug L. Hill MBA & Edmond Lou PhD

  2. Department of Electrical and Computer Engineering, University of Alberta, 116 St. and 85 Ave., Edmonton, Alberta, T6G 2R3, Canada

    Edmond Lou PhD

Authors
  1. Suzana Trac
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  2. Rui Zheng PhD
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  3. Doug L. Hill MBA
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  4. Edmond Lou PhD
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Corresponding author

Correspondence to Edmond Lou PhD.

Additional information

Author disclosures: ST (none), RZ (none), DLH (none), EL (none).

Funding Sources: Women and Children’s Health Research Institute (RES0014582), and Scoliosis Research Society (RES0024516).

Ethics approval was granted from the local health research ethics board.

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Trac, S., Zheng, R., Hill, D.L. et al. Intra- and Interrater Reliability of Cobb Angle Measurements on the Plane of Maximum Curvature Using Ultrasound Imaging Method. Spine Deform 7, 18–26 (2019). https://doi.org/10.1016/j.jspd.2018.06.015

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  • DOI: https://doi.org/10.1016/j.jspd.2018.06.015

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