3-dimensional surface measurement of spinal deformities with video rasterstereography

Abstract

Video rasterstereography is a method for back surface measurement comprising automatic back surface reconstruction and shape analysis. Aim of this prospective study was to determine the accuracy of this method in comparison to the conventional frontal and lateral standing radiographs. 95 patients with idiopathic scoliosis or scoliotic postural abnormalities and 18 patients with thoracic hyperkyphosis and Scheuermann's disease were investigated. The Cobb angles, the sagittal profile and apical vertebral rotation as well as pelvic obliquity and trunk decompensation were measured. The analysis was carried out by two independent observers. The root mean square (r.m.s.) deviation of the Cobb angle in the cases of idiopathic scoliosis ranged between 7 degrees and 8 degrees. In video rasterstereography there were no false negative results and two false positive results concerning differentiation between structural scoliosis and scoliotic postural abnormality. The r.m.s. deviation of apical vertebral rotation averaged 7.9 degrees and for pelvic obliquity respectively trunk imbalance 0.65 cm respectively 1.07 cm. The thoracic hyperkyphosis in Scheuermann's disease showed a r.m.s. deviation of 5.6 degrees. Video rasterstereography is a reliable method in the three-dimensional evaluation of spinal deformities and constitutes a valuable additional tool to the clinical examination and can reduce the number of radiographs.