A comparison of three methods for measuring thoracic kyphosis: implications for clinical studies

Objectives. To compare the Cobb technique for measuring kyphosis with an al ternative Cobb method and a computer-assisted curve assessment technique, a nd to examine the influence of vertebral body and disc shape on kyphosis. Methods. Kyphosis measurements were derived from 93 lateral spinal radiogra phs or sagittal computed tomography images of cadaveric spines, using: (i) a computer-assisted method for estimating radius of curvature; (ii) the tra ditional Cobb method and (iii) an alternative Cobb method. Regression model s were applied for agreement analyses, and to examine the relative contribu tion of vertebral body and disc shape on the extent of curvature. Results and conclusions. Strong associations existed between curvature and angle data derived from the three methods. confirming the clinical utility of these techniques for the quantification of thoracic kyphosis. However, t he traditional Cobb method tended to overestimate kyphosis in the presence of vertebral body end-plate deformation. The degree of kyphosis was strongl y reflective of the extent of deformity of the vertebral bodies, and to a l esser extent the shape of the thoracic discs.