Calculation of 3-D deformity in scoliosis by standard roentgenograms

The standard radiological diagnosis of advanced scoliosis consists of roentgenograms of the total spine in anterior-posterior and lateral views. The deformity of the spine is measured by using the Cobb angle, thus only giving the projected angle of deformity, without showing the true 3-dimensional aspect. The 3-D calculation of the deformity is relevant to diagnosis and therapy of scoliosis. In this paper we define angles according to the Cobb definition, evaluate them trigonometrically and show them in two tables. These angles allow the 3-dimensional deformity in scoliosis to be calculated using the standard roentgenograms in two perpendicular views. This procedure enables us to avoid techniques costly in time and effort in hospital routine, such as stereo radiography, computer-analysis or 3-dimensional reconstruction of CT- and MRI-investigations.