The Risk of Spinal Cord Ischemia in Thoraco-Lumbar Spine Surgery: Attempt to Quantify Predictive Factor

Background: The anterior spinal network is a major vascular system irrigating more than ¾ of the spinal cord. The origin of Adamkiewicz's Artery (AKA) is located between the 9th thoracic (T9) segment to the 2nd lumbar (L2) segment, coming from the left side for 85% of cases; between T12- L3 for 84% of cases or between T9-T10 for 50% of cases. The anterior spinal artery's syndrome (ASA syndrome) is involved in more than 90% of cases of spinal cord ischemia. The spinal cord ischemia remains one of the most serious complications after thoracolumbar spine surgery. It is difficult to quantify the risk depending on the type of surgery, the vertebral level implicated in surgery, the patient's vascular network. During planification before an elective spine surgery, the patient must receive complete information about potential risk focused on neurological and vascular damage. The objective of this work is to provide a review of the literature relating the frequency to such complications in order to inform as precisely as possible to our patient about the risk of neurologic event. It seems to be difficult to assess the risk of paraplegia during thoracolumbar spine surgery or to predict the neurological impact of an arterial sacrifice of the anterior spinal artery system. Secondary aim of this work is a reporting of the spinal cord ischemia risk factors encountered in spinal surgery in the literature. Methods: The inclusion criteria used are about patients who have suffered from neurovascular complications after thoraco-lumbar spine surgery, in relationship to the anterior spinal vascular system. We used the following key words in English: spinal cord ischemia, vascular surgical procedures, spine surgery and injury of Adamkiewicz's artery. We focused our review on major spinal surgery series of the literature which described neurologic and/or vascular complications occurring on deformity, tumoral or degenerative indications for spinal surgery. We excluded surgical complications related to traumatic spine, to another artery not directly involved in the anterior spinal network (aorta, iliac artery), to the vascular complications secondary to acute or chronic spinal vasculopathy or any ischemia not induced by spinal surgery. Results: Focusing on spine thoracic vascularization, an area devoided of artery feedings towards the second and the third thoracic segments (T2-T3) is well identified as a high risk of spinal ischemia. If an injury occurred, this area has no vascular suppleance, a possible paraplegia due to hypoperfusion can't be avoided. The surgical approaches with a higher risk of AKA's meeting are vertebrectomies for spinal metastasis removing, anterior spinal approaches or transforaminal approach for performing an arthrodesis, surgical approaches for deformity spinal surgery (scoliosis) or herniated disc surgery in thoracolumbar spinal surgery (T7-L4). The rate of neurological complications in spinal surgery is less than 6% depending on the type of surgery. Conclusions: The AKA is considered as a vascular moderator, associated with variation of blood flow from the aorta. It is involved in a spinal vascular network with a large number of anastomosis.