The lumbar autonomic nerves in males: a few anatomical insights into anterior lumbar interbody fusion

Lumbar autonomic nerve injury is an underappreciated complication of anterior lumbar spinal surgery. A detailed description of lumbar autonomic nerve anatomy would be helpful for surgeons to minimize the risk of this complication. This study was designed to investigate the anatomical characteristics of lumbar autonomic nerves and provide a better understanding of these nerves for anterior lumbar spinal surgery. A dissection-based study of 10 embalmed male cadavers. The lumbar autonomic nerves from 10 embalmed male cadavers were dissected in this study. The position of the lumbar sympathetic trunks was recorded. Distance between the initial sites of the lumbar splanchnic nerves (LSNs) and the corresponding lumbar vertebral inferior endplate, distance between the ipsilateral and adjacent LSNs, angles formed by the LSNs and the vertical axis were measured. This study has been supported by grants from Science and Technology Planning Project of Guangdong Province (CN) (Grant No. 2017B020210010) without potential conflict of interest-associated biases in the text of the paper. In this study, a total of 72 LSNs were identified in the 10 human cadavers. On average, the investigation found that the initial sites of the first, second, third, and fourth LSNs were 9 mm distal, 5 mm distal, 9 mm proximal, and 9 mm distal to the inferior endplates of the L1, L2, L3, and L4 vertebrae, respectively, with variations from 6 to 11 mm for each nerve among specimens. There was no significant difference in the angle between each lumbar splanchnic nerve and the vertical axis (H=2.461, p=.482), with an angle of approximately 50°±6°. The distance between the first and the second LSNs, the second and the third LSNs, or the third and the fourth LSNs were 24±6 mm, 22±8 mm, and 55±11 mm, respectively. The bilateral lumbar sympathetic trunks (N=57, 95%) were more likely to be located in the first third of the sagittal plane at the level of the L2/3, L3/4, and L4/5 intervertebral discs. The study found the same number and parallel courses of LSNs on each side, and on both the left and right side, the distance between the third and the fourth LSNs was much larger than the distance between the other two adjacent LSNs. The initial sites of 80.6% (n=58) of LSNs were superior to the inferior endplate of the L3 vertebra. Improved knowledge of lumbar autonomic nerve anatomy may be of great significance in reducing complications and improving surgical safety.