Kyphosis angle evaluated by video rasterstereography – relation to X-ray measurements

Abstract

Background\rSurface topography evaluations are prone to technical errors due to postural sway of the patients measured. The technical error of lateral deviation (rms) and surface rota- tion (rms) may vary between 15 and 20%, while the kyphosis angle (IP-ITL) has a technical error of only 5% (2,5°), which is comparable to the x-ray measurement. Purpose of this study was to investigate the hypothesis that video rasterstereography can be used for prognostica- tion of a kyphosis patient.\rMaterials and methods\rFifty three patients (23 females, 30 males, average age 17 years with a range from 11 to 56 years) undergoing in- patient rehabilitation have been measured with the help of video rasterstereography (VRS) before starting the treat- ment program and the values for kyphosis angle have been correlated to the kyphosis angle measured on a lat- eral x-ray (XR) not longer than 6 weeks before VRS meas- urement. 26 had a thoracic Scheuermann, 3 a thoracolumbar, 15 an Idiopathic Kyphosis and 9 a kypho- sis of other origin.\rResults\rAverage kyphosis angle XR was 49° (SD 17) and VRS 63° (SD 13). There was a high significant Pearson correlation of 0.78 and a high significant difference of 14° in the t-test (t -9,6, p < 0,001).\rConclusion\rThe kyphosis angle VRS (Vertebra prominens – lower neu- tral zone of inclination) seems to allow a follow-up of\rindividual kyphosis patients. The XR kyphosis angle according to Stagnara is measured from T4 to the lower end vertebra and therefore is lower than the VRS kyphosis angle measured from T1. The difference found between XR and VRS kyphosis angles may be explained by the angle between T1 (VRS) and T4 (XR) differently used as the upper end vertebra. Therefore, the prognostication of an individual patient is possible within certain limits