• Myung-Hoon Shin and Kyeong-Sik Ryu.
• Department of Neurosurgery, Incheon St Mary's Hospital, College of Medicine, The Catholic University of Korea, Incheon, South Korea.
• J Neurosurg Sci. 2017 Dec 1; 61 (6): 579-588.

BackgroundWe determined the optimal approach to perform lateral lumbar interbody fusion (LLIF) to treat lumbar degenerative scoliosis (LDS) by comparing the safe zone and psoas muscle on the concave and convex sides.MethodsPatients without scoliosis (N.=52) and those with levoscoliosis (N.=55) and dextroscoliosis (N.=53) were included. Vertebral anteroposterior diameter, overlap between the retroperitoneal vessels and the anterior edge of the vertebra, and overlap between the ventral nerve roots and the posterior edge of the vertebra were measured, and safe zones were calculated. The cross-sectional area (CSA) and fatty infiltration (FI) rate of the bilateral psoas muscle were measured, and the convex and concave sides were compared.ResultsThe ventral overlap on the convex side decreased at the L3-4 and L4-5 levels in the levoscoliosis group (P=0.05 and P=0.01, respectively) and at the L2-3 and L3-4 levels in the dextroscoliosis group (P=0.01 and P=0.03, respectively). The convex side at the L3-4 and L4-5 levels presented a greater safe zone in the levoscoliosis group (76.11% vs. 74.00% at L3-4, P=0.02; 69.37% vs. 63.16% at L4-5, P=0.00). The convex side at the L2-3, L3-4, and L4-5 levels in the dextroscoliosis group showed greater safe zones compared to those in the group without scoliosis (77.78% vs. 74.40% at L2-3, P=0.02; 72.15% vs. 69.87% at L3-4, P=0.03; and 58.45% vs. 54.39% L4-5 level, P=0.01). CSA of the psoas muscle on the concave side was significantly higher at the L2-3 and L3-4 levels (P=0.02 and 0.01, respectively). The psoas muscle on the concave side was significantly thicker (P=0.00 at all levels) with a higher FI rate.ConclusionsThe convex retroperitoneal vessels were positioned more anteriorly, whereas the ventral nerve roots lacked significant positional alterations, increasing the convex safe zone and providing optimal disc space access and less psoas muscle injury.

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