Avulsion of ascending lumbar and iliolumbar veins in anterior spinal surgery: an anatomical study.

To expose the disc between the 4th and 5th lumbar vertebrae in anterior spinal surgery, left to right retraction of inferior vena cava and aorta is required. This manoeuvre can be complicated by venous haemorrhage that, in most cases, is due to avulsion of the left ascending lumbar vein (ALV) or the left iliolumbar vein (ILV). We dissected 23 embalmed cadavers to assess the factors that contribute to the risk of tearing these two veins during retraction. We describe a triangular region that should help surgeons in identifying the ALV and ILV. This triangle is defined by the lateral border of the common iliac vein, the medial border of the psoas major muscle, and the superior end-plate of the L5 vertebral body. We observed that 3 cm between the termination of the left ALV, or a common stem with the ILV, and the termination of the common iliac vein is the critical distance, less than which the risk of venous avulsion is highest. Although the sample considered is small, our study seems to suggest that male patients tend to have a higher risk of venous avulsion than female patients.