Expressing Cobb Angle as Linear Measurement in Scoliosis and Its Significance: A Clinical and Geometrical Analysis of Scoliosis

OBJECTIVE The aim of this study was to formulate an objective clinical and geometric relationship between Cobb angle and the difference between the lengths of convex and concave sides (convexo-concave vertebral difference) of the structural curve in scoliosis. Is it possible to express Cobb angle in such a way that it could be visualized as a length, especially while planning for surgical correction of scoliosis? METHODS Thirty consecutive patients below the age of 19 years with a scoliosis of Cobb angle more than 10 degrees were included in the study. Convexo-concave vertebral difference of the structural curve was measured. Its relationship with the measure of Cobb angle was studied. RESULTS Author obtained a significant linear correlation between the convexo-concave vertebral differences and the Cobb angle. Using the formula Y=2d.Sin (X/2) the convexo-concave vertebral difference could be predicted. The difference thus obtained gives a quantitative measure of the maximum length of correction possible in the structural curve. CONCLUSION It is possible to express the Cobb angle as a function of linear measurement. The author proposes that this would aid the surgeons to accurately and predictably achieve the desired scoliosis correction.