Intra- and Interobserver Reliability of the Cobb Angle-Vertebral Rotation Angle-Spinous Process Angle for Adolescent Idiopathic Scoliosis

Amanda C Y Chan; Devlin G Morrison; Duc V Nguyen; Douglas L Hill; Eric Parent; Edmond H M Lou

doi:10.1016/j.jspd.2014.02.006

Intra- and Interobserver Reliability of the Cobb Angle-Vertebral Rotation Angle-Spinous Process Angle for Adolescent Idiopathic Scoliosis

Spine Deform. 2014 May;2(3):168-175. doi: 10.1016/j.jspd.2014.02.006. Epub 2014 May 8.

Authors

Amanda C Y Chan¹, Devlin G Morrison², Duc V Nguyen³, Douglas L Hill⁴, Eric Parent⁵, Edmond H M Lou⁶

Affiliations

¹ Department of Surgery, University of Alberta, 2D, Walter C Mackenzie Health Sciences Centre, 8440 - 112 Street, Edmonton, Canada T6G 2B7; Schulich School of Engineering, University of Calgary, 2500 University Drive NW, Calgary, Canada T2N 1N4.
² Department of Surgery, University of Alberta, 2D, Walter C Mackenzie Health Sciences Centre, 8440 - 112 Street, Edmonton, Canada T6G 2B7; Department of Electrical and Computer Engineering, University of Alberta, 2nd Floor, ECERF, 9107 - 116 Street, Edmonton, Canada T6G 2V4.
³ Department of Surgery, University of Alberta, 2D, Walter C Mackenzie Health Sciences Centre, 8440 - 112 Street, Edmonton, Canada T6G 2B7.
⁴ Department of Surgery, University of Alberta, 2D, Walter C Mackenzie Health Sciences Centre, 8440 - 112 Street, Edmonton, Canada T6G 2B7; Rehabilitation Research and Technology Development, Glenrose Rehabilitation Hospital, Alberta Health Services, 10230 111 Ave NW, Edmonton, Canada T5G 0B7.
⁵ Department of Physical Therapy, University of Alberta, 8205 114 St, 2-50 Corbett Hall, Edmonton, Canada T6G 2G4.
⁶ Department of Surgery, University of Alberta, 2D, Walter C Mackenzie Health Sciences Centre, 8440 - 112 Street, Edmonton, Canada T6G 2B7; Department of Electrical and Computer Engineering, University of Alberta, 2nd Floor, ECERF, 9107 - 116 Street, Edmonton, Canada T6G 2V4; Rehabilitation Research and Technology Development, Glenrose Rehabilitation Hospital, Alberta Health Services, 10230 111 Ave NW, Edmonton, Canada T5G 0B7. Electronic address: elou@ualberta.ca.

PMID: 27927414
DOI: 10.1016/j.jspd.2014.02.006

Abstract

Study design: A reliability analysis of Cobb angle, vertebral rotation (VR), and spinous process angle (SPA) measurements in adolescent idiopathic scoliosis.

Objective: To determine the intra- and interobserver reliability of semi-automated digital radiograph measurements.

Summary of background data: Cobb angle measurements on posteroanterior radiographs are commonly used to determine the severity of scoliosis. Vertebral rotation helps assess scoliosis 3-dimensionally and has a role in predicting curve progression. Recent studies have shown that the spinous process angle is a useful parameter in assessing scoliosis when using ultrasound imaging. Because the reliability of SPA measurements on radiographs has yet to be determined, it is important to compare the reliability of these 3 parameters (Cobb angle, VR, and SPA) using a computer assisted semi-automated method.

Methods: Sixty posteroanterior radiographs of patients with adolescent idiopathic scoliosis were obtained and measured twice by 3 observers who were blinded to their previous measurements, using an in-house developed program. Measurements were obtained using a semi-automated method to minimize variability resulting from observer reliability. The intra- and interobserver reliabilities were analyzed using intra-class correlation coefficients (ICCs) as well as Bland-Altman's bias and limits of agreement.

Results: Over 350 (intra) and 90 (inter) sets of curves with an average Cobb angle of 26° ± 9° (range, 10° to 44°) were compared for each parameter. Intra-observer reliabilities for each parameter were excellent (ICC_[2,1], .82; 1.00), with mean absolute differences under 3° between most measurements. Interobserver reliability (ICC_[2,1], .72; .95) was mostly good to excellent, with mean absolute differences ranging from 2.0° to 5.6°.

Conclusions: Both the intra- and interobserver assessment of the Cobb, VR, and SPA from the semi-automated measurements had clinically acceptable reliability ranges and may be considered for clinical implementation. Additional studies will be conducted to determine the accuracy and sensitivity to change of these scoliosis severity measurements.

Keywords: Adolescent idiopathic scoliosis; Cobb angle; Intra-/interobserver reliability; Spinous process angle; Vertebral rotation.