Computer-Assisted Algorithms Improve Reliability of King Classification and Cobb Angle Measurement of Scoliosis

Study Design. Interobserver and intraobserver reliability study of improved method to evaluate radiographs of patients with scoliosis. Objective. To determine the reliability of a computer-assisted measurement protocol for evaluating Cobb angle and King et al classification. Summary of Background Data. Evaluation of scoliosis radiographs is inherently unreliable because of technical and human judgmental errors. Objective, computer-assisted evaluation tools may improve reliability. Methods. Posteroanterior preoperative radiographic images of 27 patients with adolescent idiopathic scoliosis were each displayed on a computer screen. They were marked 3 times in random sequence by each of 5 evaluators (observers) who marked 70 standardized points on the vertebrae and sacrum in each radiograph. A computer program (Spine 2002;27:2801–5) that identified curves, calculated Cobb angles, and generated the King et al classification automatically analyzed coordinates of these points. The interobserver and intraobserver variability of the Cobb angle and King et al classification evaluations were quantified and compared with values obtained by unassisted observers. Results. Average Cobb angle intraobserver standard deviation was 2.0° for both the thoracic and lumbar curves (range 0.1 to 8.3° for different curves). Interobserver reliability was 2.5° for thoracic curves and 2.6° for lumbar curves. Among the 5 observers, there was an inverse relationship between repeatability and time spent marking images, and no correlation with image quality or curve magnitude. Kappa values for the variability of the King et al classification averaged 0.85 (intraobserver). Conclusions. Variability of Cobb measurements compares favorably with previously published series. The classification was more reliable than achieved by unassisted observers evaluating the same radiographs. The same principles may be applicable to other radiographic measurement and evaluation procedures.

[1]  R. Cummings,et al.  Interobserver Reliability and Intraobserver Reproducibility of the System of King et al. for the Classification of Adolescent Idiopathic Scoliosis* , 1998, The Journal of bone and joint surgery. American volume.

[2]  J. Birch,et al.  Measurement of scoliosis and kyphosis radiographs. Intraobserver and interobserver variation. , 1990, The Journal of bone and joint surgery. American volume.

[3]  I. Stokes,et al.  Identifying Sources of Variability in Scoliosis Classification Using a Rule-Based Automated Algorithm , 2002, Spine.

[4]  J. Ouellet,et al.  Comparison of Reliability Between the Lenke and King Classification Systems for Adolescent Idiopathic Scoliosis Using Radiographs That Were Not Premeasured , 2003, Spine.

[5]  R. Betz,et al.  Adolescent Idiopathic Scoliosis: A New Classification to Determine Extent of Spinal Arthrodesis , 2001, The Journal of bone and joint surgery. American volume.

[6]  H Labelle,et al.  Diurnal Variation of Cobb Angle Measurement in Adolescent Idiopathic Scoliosis , 1993, Spine.

[7]  B. Hannes,et al.  Multisurgeon Assessment of Coronal Pattern Classification Systems for Adolescent Idiopathic Scoliosis: Reliability and Error Analysis , 2002, Spine.

[8]  J. Sevastik,et al.  Accuracy and applicability of measurement of the scoliotic angle at the frontal plane by Cobb's method, by Ferguson's method and by a new method , 2004, European Spine Journal.

[9]  E. Hall,et al.  Measurement of the Cobb angle on radiographs of patients who have scoliosis. Evaluation of intrinsic error. , 1990, The Journal of bone and joint surgery. American volume.

[10]  Bert Verdonck,et al.  The reliability of quantitative analysis on digital images of the scoliotic spine , 2002, European Spine Journal.

[11]  Michael Nogler,et al.  Interobserver and Intraobserver Reliability of Lenke’s New Scoliosis Classification System , 2002, Spine.

[12]  David Clements,et al.  Curve Prevalence of a New Classification of Operative Adolescent Idiopathic Scoliosis: Does Classification Correlate With Treatment? , 2002, Spine.

[13]  H Labelle,et al.  Observer Variation in Assessing Spinal Curvature and Skeletal Development in Adolescent Idiopathic Scoliosis , 1988, Spine.

[14]  Jacob Cohen.  A Coefficient of Agreement for Nominal Scales , 1960 .

[15]  R. Winter,et al.  The selection of fusion levels in thoracic idiopathic scoliosis. , 1983, The Journal of bone and joint surgery. American volume.

[16]  J. Pruijs,et al.  Parameter variation in stable scoliosis , 2004, European Spine Journal.

[17]  R R Betz,et al.  Intraobserver and Interobserver Reliability of the Classification of Thoracic Adolescent Idiopathic Scoliosis*† , 1998, The Journal of bone and joint surgery. American volume.

[18]  E. Bleck,et al.  The Significance of Roentgenographic Measurement in Scoliosis , 1982, Journal of pediatric orthopedics.

[19]  M. Ylikoski,et al.  Measurement variations in scoliotic angle, vertebral rotation, vertebral body height, and intervertebral disc space height. , 1990, Journal of spinal disorders.