An MRI study of lateral vascular safety zones in oblique lumbar interbody fusion surgery

Abstract

To study the anatomical characteristics of blood vessels in the lateral segment of the vertebral body through the surgical approach of oblique lumbar interbody fusion (OLIF) using MRI imaging, and evaluate its potential vascular safety zone. The lumbar MRI data of 107 patients with low back and leg pain who met the selection criteria between October 2019 and November 2022 were retrospectively analyzed. The vascular emanation angles, vascular travel angles, and the length of vessels in the lateral segments of the left vertebral body of L 1-L 5, as well as the distance between the segmental vessels in different Moro junctions of the vertebral body and their distances from the edges of the vertebrae in the same sequence (bottom marked as I, top as S) were measured. The gap between the large abdominal vessels and the lateral vessels of the vertebral body was set as the lateral vascular safe zones of the lumbar spine, and the extent of the safe zones (namely the area between the vessels) was measured. The anterior 1/3 of the lumbar intervertebral disc was taken as the simulated puncture center, and the area with a diameter of 22 mm around it as the simulated channel area. The proportion of vessels in the channel was further counted. In addition, the proportions of segmental vessels at L 5 without a clear travel and with an emanation angel less than 90° were calculated. Except for the differences in the vascular emanation angles between L 4 and L 5, the vascular travel angles between L 1, L 2 and L 4, L 5, and the length of vessels in the lateral segments of the vertebral body among L 1-L 4 were not significant ( P>0.05), the differences in the vascular emanation angles, vascular travel angles, and the length of vessels between the rest segments were all significant ( P<0.05). There was no significant difference in the distance between vessels of L 1, L 2 and L 2, L 3 at Moro Ⅰ-Ⅳ junctions ( P>0.05), in L 3, L 4 and L 4, L 5 at Ⅱ and Ⅲ junction ( P>0.05). There was no significant difference in the vascular distance of L 2, L 3 between Ⅱ, Ⅲ junction and Ⅲ, Ⅳ junction, and the vascular distance of L 3, L 4 between Ⅰ, Ⅱ junction and Ⅲ, Ⅳ junction ( P>0.05). The vascular distance of the other adjacent vertebral bodies was significant different between different Moro junctions ( P<0.05). Except that there was no significant difference in the distance between L 2I and L 3S at Ⅰ, Ⅱ junction, L 3I and L 4S at Ⅱ, Ⅲ junction, and L 2I and L 3S at Ⅲ, Ⅳ junction ( P>0.05), there was significant difference of the vascular distance between the bottom of one segment and the top of the next in the other segments ( P<0.05). Comparison between junctions: Except for the L 3S between Ⅰ, Ⅱ junction and Ⅱ, Ⅲ junction, and L 5S between Ⅰ, Ⅱ junction and Ⅱ, Ⅲ and Ⅲ, Ⅳ junctions had no significant difference ( P>0.05), there were significant differences in the distance between the other segmental vessels and the vertebral edge of the same sequence in different Moro junctions ( P<0.05). The overall proportion of vessels in the simulated channels was 40.19% (43/107), and the proportion of vessels in L 1 (41.12%, 44/107) and L 5 (18.69%, 20/107) was higher than that in the other segments. The proportion of vessels in the channel of Moro zone Ⅰ (46.73%, 50/107) and zone Ⅱ (32.71%, 35/107) was higher than that in the zone Ⅲ, while no segmental vessels in L 1 and L 2 were found in the channel of zone Ⅲ ( χ 2=74.950, P<0.001). Moreover, 26.17% (28/107) of the segmental vessels of lateral L 5 showed no movement, and 27.10% (29/107) vascular emanation angles of lateral L 5 were less than 90°. L 1 and L 5 segmental vessels are most likely to be injured in Moro zones Ⅰ and Ⅱ, and the placement of OLIF channels in L 4, 5 at Ⅲ, Ⅳ junction should be avoided. It is usually safe to place fixation pins at the vertebral body edge on the cephalic side of the intervertebral space, but it is safer to place them on the caudal side in L 1, 2 (Ⅰ, Ⅱ junction), L 3, 4 (Ⅲ, Ⅳ junction), and L 4, 5 (Ⅱ, Ⅲ, Ⅳ junctions).