A Study of the Sagittal Angle of Lumbar Bicortical Pedicle Screws from the Anatomic Perspective of the Lumbar Artery.

Abstract

To observe anatomic relationships between lumbar bicortical pedicle screws (BPSs) at 2 sagittal section angles (SSAs) and lumbar artery (LA). We observed 2 SSAs, vertical angle and cephalic angle, of the BPS. The positions at which the BPS breaks through the anterior vertebral cortex were defined as point A and point B. Distances from point A and point B to LAs were measured. The percentage of risk of injury to LAs was calculated according to these distances. At the same transverse section angle on the left and right side in L1 and L2, distance from point A to LA was significantly greater than distance from point B to LA (P < 0.001) except at a transverse section angle of 0° on the right side in L2 (P > 0.05). At the same transverse section angle on the left in L3 and L4, distance from point B to LA was significantly greater than distance from point A to LA (P < 0.001). The percentages of high risk of injury to the LA resulting from BPSs at the vertical angle in L1 and L2 were 0%-6.2%. The percentages of high risk of injury to the LA resulting from BPSs at the cephalic angle on the left side in L3 and L4 were 0%-18.5%. Lumbar BPSs present a risk of injury to the LA. The vertical angle is the recommended SSA for BPSs in L1 and L2, and the cephalic angle is the recommended SSA in L3 and L4.