title: MRI-based determination of convex or concave surgical approach for lateral lumbar interbody fusion in lumbar degenerative scoliosis: a retrospective radiographic comparative analysis.
abstract: BACKGROUND
  We 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.
  
  
  METHODS
  Patients 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Department of Neurosurgery, Incheon St Mary's Hospital, College of Medicine, The Catholic University of Korea, Incheon, South Korea.
authors.forename: Myung-Hoon
authors.initials: MH
authors.lastname: Shin
authors.affiliation: Department of Neurosurgery, Seoul St Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, South Korea - novice97@hanmail.net.
authors.forename: Kyeong-Sik
authors.initials: KS
authors.lastname: Ryu
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000379:methods; D012189:Retrospective Studies; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*