Manual and Computerized Measurement of Sagittal Vertebral Inclination in Computed Tomography Images

Study Design. Sagittal vertebral inclination (SVI) was systematically evaluated in computed tomography (CT) images by three observers using six manuals and two computerized measurements. Objective. To analyze and compare manual and computerized measurements of SVI in CT images. Summary of Background Data. A number of methods were proposed to measure SVI in lateral radiographic projections in the form of spinal curvature or segmental angulation. A systematic analysis of the manual and computerized measurements in sagittal CT cross-sections has not been performed yet. Methods. SVI was measured in CT images for 28 vertebrae independently by three observers. Manual measurements were obtained in sagittal cross-sections by manually identifying the vertebral body corners, which defined the lines of SVI (superior and inferior tangents, anterior and posterior tangents, mid-endplate and mid-wall lines) against reference horizontal or vertical lines. Computerized measurements were obtained by manually identifying the vertebral centroids, which initialized the automated method that evaluated SVI by searching for the planes of maximal symmetry of vertebral bodies in two dimensions and in three dimensions. Results. The midwall lines proved to be the most reproducible and reliable manual measurements (1.0 degrees and 1.4 degrees standard deviations [SD]). The computerized measurements in three dimensions were more reproducible and reliable (0.9 degrees and 1.3 degrees SD) and also most consistent with the midwall lines (2.1 degrees SD and 1.7 degrees mean absolute difference). Conclusions. The manual measurements based on mid-wall lines and the computerized measurements in three dimensions yielded the lowest intraobserver and interobserver variability of SVI. However, in terms of speed and operator friendliness, the computerized measurements may represent an adequate alternative to manual measurements.