Radiographic vs. direct measurements of the spinal canal of the thoracolumbar junctional region (T10-L1) of the spine.

Midsagittal diameter (MSD) and interpedicular distance (IPD) in the thoracolumbar junctional region (T10-L1) of 24 male cadaveric spines were measured both from radiographs and directly from bones after removal of the soft tissues in order to assess the accuracy of plain radiographs. In addition surface areas of the vertebral canals were measured also from bone samples. It was found that the mean difference between bone and radiographic measurements in the IPD on different vertebral levels was 1.0 mm (r = 0.98). The MSD was a more difficult measurement, but the correlation coefficient was still 0.70, the mean difference being 0.7 mm or less. The sum of the MSD and IPD showed good relationship with the cross sectional area of the spinal canal, and the correlation coefficient was 0.77 (P less than 0.001).