• Tri Arief Sardjono, Michael H F Wilkinson, Albert G Veldhuizen, Peter M A van Ooijen, Ketut E Purnama, and Gijsbertus J Verkerke.
• *Institut Teknologi Sepuluh Nopember, Surabaya, Jawa Timur, Indonesia; †Johann Bernoulli Institute of Mathematics and Computer Science, University of Groningen, Groningen, The Netherlands; ‡Department of Orthopaedic Surgery, University of Groningen, University Medical center Groningen, Groningen, The Netherlands; §Department of Radiology, University of Groningen, University Medical center Groningen, Groningen, The Netherlands; ¶Department of Electrical Engineering, Institute of Technology Institut Teknologi Sepuluh Nopember (ITS), Surabaya, Indonesia; ‖Department of Rehabilitation Medicine, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; and **Department of Biomechanical Engineering, University of Twente, Enschede, The Netherlands.
• Spine. 2013 Sep 15; 38 (20): E1256-62.

Study DesignAutomatic measurement of Cobb angle in patients with scoliosis.ObjectiveTo test the accuracy of an automatic Cobb angle determination method from frontal radiographical images.Summary Of Background DataThirty-six frontal radiographical images of patients with scoliosis.MethodsA modified charged particle model is used to determine the curvature on radiographical spinal images. Three curve fitting methods, piece-wise linear, splines, and polynomials, each with 3 variants were used and evaluated for the best fit. The Cobb angle was calculated out of these curve fit lines and compared with a manually determined Cobb angle. The best-automated method is determined on the basis of the lowest mean absolute error and standard deviation, and the highest R2.ResultsThe error of the manual Cobb angle determination among the 3 observers, determined as the mean of the standard deviations of all sets of measurements, was 3.37°. For the automatic method, the best piece-wise linear method is the 3-segments method. The best spline method is the 10-steps method. The best polynomial method is poly 6. Overall, the best automatic methods are the piece-wise linear method using 3 segments and the polynomial method using poly 6, with a mean absolute error of 4,26° and 3,91° a standard deviation of 3,44° and 3,60°, and a R2 of 0.9124 and 0.9175. The standard measurement error is significantly lower than the upper bound found in the literature (11.8°).ConclusionThe automatic Cobb angle method seemed to be better than the manual methods described in the literature. The piece-wise linear method using 3 segments and the polynomial method using poly 6 yield the 2 best results because the mean absolute error, standard deviation, and R2 are the best of all methods.Level Of Evidence3.

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