title: Reliability analysis of Cobb angle measurements of congenital scoliosis using X-ray and 3D-CT images.
abstract: OBJECTIVE
  Therapeutic decisions for congenital scoliosis rely on Cobb angle measurements on consecutive radiographs. There have been no studies documenting the variability of measuring the Cobb angle using 3D-CT images in children with congenital scoliosis. The purpose of this study was to compare the reliability and measurement errors using X-ray images and those utilizing 3D-CT images.
  
  
  METHODS
  The X-ray and 3D-CT images of 20 patients diagnosed with congenital scoliosis were used to assess the reliability of the digital 3D-CT images for the measurement of the Cobb angle. Thirteen observers performed the measurements, and each image was analyzed by each observer twice with a minimum interval of 1 week between measurements. The analysis of intraobserver variation was expressed as the mean absolute difference (MAD) and standard deviation (SD) between measurements and the intraclass correlation coefficient (IaCC) of the measurements. In addition, the interobserver variation was expressed as the MAD and interclass correlation coefficient (IeCC).
  
  
  RESULTS
  The average MAD and SD was 4.5° and 3.2° by the X-ray method and 3.7° and 2.6° by the 3D-CT method. The intraobserver and interobserver intraclass ICCs were excellent in both methods (X-ray: IaCC 0.835-0.994 IeCC 0.847, 3D-CT: IaCC 0.819-0.996 IeCC 0.893). There was no significant MAD difference between X-ray and 3D-CT images in measuring each type of congenital scoliosis by each observer.
  
  
  CONCLUSIONS
  Results of Cobb angle measurements in patients with congenital scoliosis using X-ray images in the frontal plane could be reproduced with almost the same measurement variance (3°-4° measurement error) using 3D-CT images. This suggests that X-ray images are clinically useful for assessing any type of congenital scoliosis about measuring the Cobb angle alone. However, since 3D-CT can provide more detailed images of the anterior and posterior components of malformed vertebrae, the volume of information that can be obtained by evaluating them has contributed greatly to the development of strategies for the surgical treatment of congenital scoliosis.
authors.affiliation: Department of Orthopedics and Spine Surgery, Meijo Hospital, 1-3-1, Sannomaru, Naka-ku, Nagoya, 460-0001, Japan.
authors.forename: Ryoji
authors.initials: R
authors.lastname: Tauchi
authors.affiliation: Department of Orthopedics and Spine Surgery, Meijo Hospital, 1-3-1, Sannomaru, Naka-ku, Nagoya, 460-0001, Japan.
authors.forename: Taichi
authors.initials: T
authors.lastname: Tsuji
authors.affiliation: Department of Orthopedic Surgery, Shriners Hospitals for Children-Philadelphia, Philadelphia, PA, USA.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Cahill
authors.affiliation: Division of Orthopaedics, Children's Hospital of Philadelphia, Philadelphia, PA, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Flynn
authors.affiliation: Department of Pediatric Orthopaedic Surgery, Hospital la Conception, San German, PR, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Flynn
authors.affiliation: Department of Orthopaedic Surgery, Children's Hospital Boston, Boston, MA, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Glotzbecker
authors.affiliation: Division of Pediatric Orthopaedics, Isaac Walton Killam Health Centre, Halifax, NS, Canada.
authors.forename: Ron
authors.initials: R
authors.lastname: El-Hawary
authors.affiliation: Department of Orthopaedic Surgery, Emory University School of Medicine, Emory Spine Center, Atlanta, GA, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Heflin
authors.affiliation: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Imagama
authors.affiliation: South Texas Spinal Clinic, San Antonio, TX, USA.
authors.forename: Ajeya P
authors.initials: AP
authors.lastname: Joshi
authors.affiliation: Department of Orthopedics and Spine Surgery, Meijo Hospital, 1-3-1, Sannomaru, Naka-ku, Nagoya, 460-0001, Japan.
authors.forename: Ayato
authors.initials: A
authors.lastname: Nohara
authors.affiliation: Department of Pediatric Orthopaedic Surgery, Hospital la Conception, San German, PR, USA.
authors.forename: Norman
authors.initials: N
authors.lastname: Ramirez
authors.affiliation: Department of Pediatric Orthopaedic Surgery, Columbia University Medical Center, New York, NY, USA.
authors.forename: David P
authors.initials: DP
authors.lastname: Roye
authors.affiliation: Department of Orthopedics and Spine Surgery, Meijo Hospital, 1-3-1, Sannomaru, Naka-ku, Nagoya, 460-0001, Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Saito
authors.affiliation: Campbell Clinic, University of Tennessee, Memphis, TN, USA.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Sawyer
authors.affiliation: Department of Orthopaedics, University of Utah, Salt Lake City, UT, USA.
authors.forename: John T
authors.initials: JT
authors.lastname: Smith
authors.affiliation: Department of Orthopedics and Spine Surgery, Meijo Hospital, 1-3-1, Sannomaru, Naka-ku, Nagoya, 460-0001, Japan. nupriver@gmail.com.
authors.forename: Noriaki
authors.initials: N
authors.lastname: Kawakami
mesh_terms: D002648:Child; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012600:Scoliosis / Q000151:congenital / Q000000981:diagnostic imaging / Q000473:pathology*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed
keywords: Children; Cobb angle; Computed tomography; Congenital scoliosis; Interobserver; Intraobserver; Measurement reliability; X-ray