A Novel Computer-Aided Method to Evaluate Scoliosis Curvature using Polynomial Math Function

Abstract

Background: Scoliosis is a health problem that causes a side-to-side curvature in the spine. The curvature may have an "S" or "C" shape. To evaluate scoliosis, the Cobb angle has been commonly used. However, digital image processing allows the Cobb angle to be obtained easily and quickly, several researchers have determined that Cobb angle contains high variations (errors) in the measurements. Therefore, a more reproducible computer aided-method to evaluate scoliosis is presented.

Material and methods: In this analytical study, several polynomial curves were fitted to the spine curvature (4^th to 8^th order) of thirty plain films of scoliosis patients to obtain the Curvature-Length of the spine. Each plain film was evaluated by 3 physician observers. Curvature was measured twice using the Cobb method and the proposed Curvature-Length Technique (CLT). Data were analyzed by a paired-sample Student t-test and Pearson correlation method using SPSS Statistics 25.

Results: The curve of 7^th order polynomial had the best fit on the spine curvature and was also used for our proposed method (CLT) obtaining a significant positive correlation when compared to Cobb measurements (r=0.863, P<0.001). The Intraclass Correlation (ICC) was between 0.863 and 0.948 for Cobb method and0.974 to 0.984 for CLT method. In addition, mean measurement of the inter-observer COV (Coefficient of Variation) for Cobb method was of 0.185, that was significantly greater than the obtained with CLT method of 0.155, this means that CLT method is 16.2% more repeatable than Cobb Method.

Conclusion: Based on results, it was concluded that CLT method is more reproducible than the Cobb method for measuring spinal curvature.

Keywords: Cobb-Angle; Methods; Polynomial; Spinal Curvatures; Scoliosis.

Figure1

The angle forming at the vertex of the intersection of lines a-b and b-c which drawn parallel to the superior endplate of the superior vertebra and inferior endplate of the inferior vertebra respectively is the Cobb angle.

Figure2

A. Image adjusted the contrast of the image using adaptive histogram equalization. B. Image adjusted the intensity to emphasize vertebras.

Figure3

A. Approximate centroid localization of each vertebra from C7 to L5 B. the intersection of a-b line with the c-d line is considered as centroid (e).

Figure4

7^th Order polynomial fitted on spine deformation

Figure5

Ideal Spine vs a deformity spine (scoliosis).

Figure6

Box plot chart of variation of each radiography using CLT Method.

Figure7

Box plot chart of variation of each radiography using Cobb Method.

Figure8

COV of each radiography using CLT and COBB method.

Figure9

Pearson correlation graph between Cobb and CLT methods (r= 0.863, p<0.001).