title: Effect of lordosis angle change after lumbar/lumbosacral fusion on sacrum angular displacement: a finite element study.
abstract: OBJECTIVE
  To assess and characterize the sacrum angular displacements in response to lumbar lordosis after lumbar/lumbosacral fusion.
  
  
  METHODS
  A finite element model of the lower lumbar spine-pelvis was established and used to simulate the posterior fusion at L3-L5 and L4-S1. The lordosis angle in the fusion segments was set to five different conditions with respect to the intact model: 10° less than intact, 5° less than intact, same as intact, 5° more than intact, and 10° more than intact. Variations of the sacrum angular displacements with lordosis changes were analyzed under loading setting of axial compression, flexion, extension, lateral bending, and axial rotation.
  
  
  RESULTS
  Compared with the intact lordosis, both increased and decreased lumbar lordosis angles caused the sacrum angular displacements to be increased. The lordosis angle increased by 10° induced the most substantial increase in sacrum angular displacements. In addition, the sacrum angular displacements of the L4-S1 fusion model at different lordosis angles were higher than those of the L3-L5 fusion model.
  
  
  CONCLUSIONS
  The sacrum angular displacements occur as a result of the fusion surgery (L4-S1) and the changes in lumbar lordosis.
authors.affiliation: Orthopedic Department of Changhai Hospital, 168 Changhai Road, Shanghai, 200433, People's Republic of China.
authors.forename: Ningfang
authors.initials: N
authors.lastname: Mao
authors.forename: Jian
authors.initials: J
authors.lastname: Shi
authors.forename: Dawei
authors.initials: D
authors.lastname: He
authors.forename: Yang
authors.initials: Y
authors.lastname: Xie
authors.forename: Yushu
authors.initials: Y
authors.lastname: Bai
authors.forename: Xianzhao
authors.initials: X
authors.lastname: Wei
authors.forename: Zhicai
authors.initials: Z
authors.lastname: Shi
authors.forename: Ming
authors.initials: M
authors.lastname: Li
mesh_terms: D000328:Adult; D020342:Finite Element Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008141:Lordosis / Q000000981:diagnostic imaging* / Q000601:surgery; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D008297:Male; D009068:Movement; D065289:Pedicle Screws; D011859:Radiography; D012399:Rotation; D012447:Sacrum / Q000000981:diagnostic imaging* / Q000601:surgery*; D013123:Spinal Fusion