Evaluation of the upper sacrum by three-dimensional computed tomography.

Axial and sagittal computed tomographic (CT) scans of 40 sacrum specimens were obtained. The measurements of the upper sacral canal and S1-2 and S2-3 anterior sacral foramina were performed on axial scans, and the evaluation of the upper sacral pedicle was based on sagittal scans. The results showed that there were statistically significant differences between male and female specimens in 3 of 29 measurements. In general, the measurements of male specimens were slightly larger than those of the female specimens, and the linear dimensions of the sacral canal, anterior foramina, and pedicle decreased from the S1 to S3. This study indicated that the critical area of the sacral pedicle for screw insertion lies in the junction between the pedicle and vertebral body. CT scans provide more accurate information about the essential sacral anatomy.