The lumbar region vasculature is a retroperitoneal structure. It consists mainly of the great vessels: the aorta and vena cava, common iliac arteries and veins, and segmental vessels. Preoperative sagittal and axial MRI should be used to determine the location of the bifurcation and whether the patient has transitional anatomy.
The vena cava is located on the right of the patient while the aorta is located more midline. This anatomy allows for oblique corridor access on the patient's left side. Therefore, placing the patient in a right lateral decubitus position increases the size of the corridor because great vessels move to the right side with gravity. Bifurcation of the aorta and vena cava is most often found at the L4 vertebral body.
The common iliac vessels branch below the bifurcation. The left common iliac vein (LCIV) is often located medially and may obstruct the anterior surface of the disc at L5-S1. The OLIF51 approach accesses the L5 -S1 disc below the bifurcation of the common iliac vessels. To gain exposure of the L5-S1 disc space during the OLIF51 procedure, the LCIV can be displaced laterally with gentle retraction if necessary.
The iliolumbar vein is the segmental vein for the L5 vertebral body. It runs transversely anterior to posterior across the L5 vertebral body and turns cephalad, crossing the L4-L5 disc space posteriorly.
If the patient has transitional anatomy, the course of the iliolumbar vein may be observed at the L4-L5 disc space.
The OLIF25 procedure allows direct visualization of this vein. If the stability pin is used at L4-L5, the pin should be placed in L4 and not in L5 to help avoid injury.
The mid-sacral vessels are often encountered at the L5-S1 disc space. Once identified during the OLIF51 procedure, they can be either retracted or ligated to allow access to the disc space.