Location variance of the great vessels while undergoing side-bend positioning changes during lateral interbody fusion

Minimally invasive lateral lumbar interbody fusion (LLIF) is an increasingly popular surgical technique that facilitates minimally invasive exposure, attenuated blood loss, and potentially improved arthrodesis rates. However, there is a paucity of evidence elucidating the risk of vascular injury associated with LLIF, and no previous studies have evaluated the distance from the lumbar intervertebral space (IVS) to the abdominal vascular structures in a side-bend lateral decubitus position. Therefore, the purpose of this study is to evaluate the average distance, and changes in distance, from the lumbar IVS to the major vessels from supine to side-bend right and left lateral decubitus (RLD and LLD) positions simulating operating room positioning utilizing magnetic resonance imaging (MRI).

We independently evaluated lumbar MRI scans of 10 adult patients in the supine, RLD, and LLD positions, calculating the distance from each lumbar IVS to adjacent major vascular structures.

At the cephalad lumbar levels (L1-L3), the aorta lies in closer proximity to the IVS in the RLD position, in contrast to the inferior vena cava (IVC), which is further from the IVS in the RLD. At the L3-S1 vertebral levels, the right and left common iliac arteries (CIA) are both further from the IVS in the LLD position, with the notable exception of the right CIA, which lies further from the IVS in the RLD at the L5-S1 level. At both the L4-5 and L5-S1 levels, the right common iliac vein (CIV) is further from the IVS in the RLD. In contrast, the left CIV is further from the IVS at the L4-5 and L5-S1 levels.

Our results suggest that RLD positioning may be safer for LLIF as it affords greater distance away from critical venous structures, however, surgical positioning should be assessed at the discretion of the spine surgeon on a patient-specific basis.