Avoidance of vascular injury during trans-psoas approaches; awareness of venous anatomy on MRI.

PURPOSE: Iliolumbar venous anatomy shows many variations between individuals, which can potentially be hazardous during lumbar spine surgery. The iliolumbar veins and any large variants can be observed on routine pre-operative lumbar spine MRI. Knowledge of the venous anatomy is important during lumbar spinal surgery, to avoid any potential haemorrhagic complications. This is particularly relevant for anterior lumbar surgery and lateral trans-psoas surgery.

METHODS: In this study, we assessed the venous anatomy on the pre-operative MRI of 144 patients who underwent trans-psoas lateral access surgery over the past 15 years. Any surgical complications were also analysed.

RESULTS: The iliolumbar vein was visible in 113 patients. The iliolumbar vein was seen at L5-S1 level in 78 patients, reaching to L4- 5 in 32 patients and extending up to L3-4 in 3 patients. Only one patient had a large variant left sided ascending lumbar vein visible on the pre-operative MRI and this patient had a haemorrhagic complication during the lateral trans-psoas surgical approach. None of the other patients had any significant haemorrhagic complications.

CONCLUSION: The vascular anatomy is readily identified on the pre-operative MRI. Veins considered to be large enough to present a surgical hazard, at levels proximal to the L4-5 disc, have a diameter greater than the exiting nerve root at the same level. Review of the vascular anatomy should be performed during the surgical planning to avoid any potential haemorrhagic complications.