Are Traditional Radiographic Methods Accurate Predictors of Pedicle Morphology?

STUDY DESIGN: Cadaveric in vitro computed tomography (CT) imaging study. OBJECTIVE: To examine minimum pedicle diameter from transverse and coronal CT reconstructions of thoracolumbar spine specimens and compare their degree of disparity, if any. Pedicle angulation in coronal and transverse planes was measured and their contribution to the disparity in minimum pedicle diameter was assessed. SUMMARY OF BACKGROUND DATA: Spinal minimum pedicle diameter can be obtained from both transverse and coronal CT reconstructions; however, the degree of disparity in these measurements has not been described previously. Angulation of the pedicle in transverse and coronal planes may contribute to a disparity in minimum pedicle diameter acquired from reconstructions. This also has not been described previously. This study examined whether the disparity could be predicted by spinal level, as pedicle angulations vary in both coronal and transverse planes. METHODS: Five thoracolumbar specimens (T1-L5, age 48-59 yrs, male) were CT scanned utilizing clinical protocols. Minimum pedicle diameters and pedicle angulations were acquired in transverse and coronal reconstructions. Disparities between minimum pedicle diameters were measured and the correlation between this disparity and spinal level was characterized. RESULTS: A significant difference (P < 0.001) in minimum pedicle diameter existed between measures from coronal and transverse reconstructions. There was a significant correlation (P < 0.001) between the difference in minimal pedicle diameter and the transverse pedicle angle as well as the coronal pedicle angle. CONCLUSION: An overestimation of minimum pedicle diameter in the transverse reconstruction occurs when the coronal pedicle angulation increases, and in the coronal reconstruction when the transverse pedicle angulation increases. Therefore, pedicle angle should be determined using both coronal and transverse reconstructions and utilized to reduce the risk of overestimation of the true pedicle diameter. LEVEL OF EVIDENCE: NA.