title: Is Preventative Long-Segment Surgery for Multi-Level Spondylolysis Necessary? A Finite Element Analysis Study.
abstract: OBJECTIVE
  For multi-level spondylolysis patients, surgeons commonly choose to fix all the segments with pars interarticularis defect even those without slippage and not responsible for clinical symptoms. In this study, we tried to study the necessity of the preventative long-segment surgery for the defected segment without slippage in treatment of multi-level spondylolysis patients from a biomechanical perspective.
  
  
  METHODS
  We established a bi-level spondylolysis model with pars defects at L4 and L5 segments, and simulated posterior lumbar interbody fusion (PLIF) and pedicle screw fixation at L5-S1 level. Then we compared the biomechanical changes at L4 segment before and after surgery in neutral, flexion, extension, lateral bending and axial rotation position.
  
  
  RESULTS
  The stress on L4 pars interarticularis was very similar before and after surgery, and reached the highest in axial rotation. The L3-L4 intradiscal pressure was almost the same, while L4-L5 intradiscal pressure changed a little in lateral bending (increase from 1.993 to 2.160 MPa) and axial rotation (decrease from 1.639 to 1.307 MPa) after surgery. The PLIF surgery caused a little increase of range of motion at adjacent L4-L5 and L3-L4 levels, but the change is very tiny (1 degree).
  
  
  CONCLUSIONS
  The PLIF surgery will not cause significant biomechanical change at adjacent segment with pars defect in multi-level spondylolysis. On the contrary, excessive long-segment surgery will damage surrounding soft tissues which are important for maintaining the stability of spine. So a preventative long-segment surgery is not necessary for multi-level spondylolysis as long as there are no soft tissue degeneration signs at adjacent level.
authors.affiliation: Department of Orthopedics, The First Affiliated Hospital of Soochow University, Orthopedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, People's Republic of China.
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Mo
authors.affiliation: Department of Orthopedics, The First Affiliated Hospital of Soochow University, Orthopedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, People's Republic of China.
authors.forename: Wen
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Orthopedics, The First Affiliated Hospital of Soochow University, Orthopedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, People's Republic of China.
authors.forename: Dongyan
authors.initials: D
authors.lastname: Zhong
authors.affiliation: Department of Orthopedics, The First Affiliated Hospital of Soochow University, Orthopedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, People's Republic of China.
authors.forename: Hao
authors.initials: H
authors.lastname: Xu
authors.affiliation: Department of Orthopedics, The First Affiliated Hospital of Soochow University, Orthopedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, People's Republic of China.
authors.forename: Lan
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Orthopedics, The First Affiliated Hospital of Soochow University, Orthopedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, People's Republic of China.
authors.forename: Jia
authors.initials: J
authors.lastname: Yu
authors.affiliation: Department of Orthopedics, The First Affiliated Hospital of Soochow University, Orthopedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, People's Republic of China.
authors.forename: Zongping
authors.initials: Z
authors.lastname: Luo
mesh_terms: D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery; D011312:Pressure; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000009:adverse effects; D013169:Spondylolysis / Q000503:physiopathology / Q000601:surgery*; D013314:Stress, Mechanical