Comparison of radiographic and computed tomographic measurement of pedicle and vertebral body dimensions in Koreans: the ratio of pedicle transverse diameter to vertebral body transverse diameter.

This study was designed to investigate the characteristics of pedicle transverse diameters (PD), vertebral body transverse diameters (VBD), especially the ratios of PD/VBD (CT ratio), which has never been discussed, in Koreans using computed tomography (CT) scans and to evaluate the possibility of obtaining more accurate estimations of PD from plain radiographs using the CT ratios in each spine level. The T1-L5 vertebrae of 50 participants were analyzed prospectively with CT scans (CT-VBD and CT-PD), and the T9-L5 vertebrae of the same participants were investigated with plain radiographs (X-VBD and X-PD). The CT ratio had a higher correlation with the CT-PD (r2 = 0.630) from T1 to L5, especially in the lower thoracic and lumbar spine (T9-L5, r2 = 0.737). The correlation of VBDs between the two radiologic tools (r2 = 0.896) was higher than that of the PDs (r2 = 0.665). Based on the data, equations for the estimation of a more accurate PD from plain radiographs were developed as follows: estimated PD = estimated VBD × [1.014 × (X-VBD) + 0.152] × the mean CT ratio at each spinal level. The correlation between the estimated PD and the CT-PD (r2 = 0.852) was improved compared with that (r2 = 0.665) between the X-PD and the CT-PD. In conclusion, the CT ratio showed a very similar changing trends to CT-PD from T1 to L5 regardless of sex and body mass, and the measurement error of PD from only plain radiographs could be minimized using estimated VBD and the mean CT ratio at each spinal level.