title: The biomechanical advantages of bilateral lumbo-iliac fixation in unilateral comminuted sacral fractures without sacroiliac screw safe channel: A finite element analysis.
abstract: BACKGROUND
  The aim of this study was to compare the biomechanical characteristics between bilateral and unilateral lumbo-iliac fixation in unilateral comminuted sacral fractures (USF) by finite element analysis.
  
  
  METHODS
  A 3-dimensional finite element model of unilateral sacral fractures was simulated. Three kinds of implants were instrumented into the model, including the unilateral lumbopelvic fixation (ULF), bilateral lumbopelvic fixation (BLF), and unilateral iliac fixation with bilateral lumbar pedicle screws (UBF). Loads of compression and rotation were distributed to the superior endplate of L3. To evaluate the biomechanical properties, the construct stiffness, the micromotion of the fractures, the stress distribution of implants, and the balance of hemilumbar vertebra are recorded and analyzed.
  
  
  RESULTS
  The highest construct stiffness was provided by BLF. In BLF model, the displacement between iliums was only 0.009 mm (compressional) and 0.001 mm (rotational), which was less than that under normal condition (0.02 mm). The maximum von Misses stress of implants appeared on the UBF. By using unilateral fixation, the L4 endured obvious imbalance on bilateral hemivertebra. A marked difference was exposed in BLF and UBF models, and the equilibrium of stress and activity was shown.
  
  
  CONCLUSIONS
  From the finite element view, the stability of ULF is insufficient to reconstruct the posterior pelvic ring. Furthermore, the unilateral fixation may lead to imbalance of lumbar vertebra and pelvis. On the contrary, the BLF can provide satisfied stability and lumbar balance.
authors.affiliation: Department of Orthopedic Surgery, Provincial Hospital Affiliated to Shandong University, Ji'nan, Shandong Department of Orthopaedics, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Dongcheng District, Beijing, People's Republic of China.
authors.forename: Wenhao
authors.initials: W
authors.lastname: Song
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Zhou
authors.forename: Yu
authors.initials: Y
authors.lastname: He
mesh_terms: D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D005593:Fracture Fixation, Internal / Q000379:methods*; D018460:Fractures, Comminuted / Q000175:diagnosis / Q000601:surgery*; D006801:Humans; D007085:Ilium / Q000000981:diagnostic imaging / Q000293:injuries* / Q000601:surgery; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000293:injuries* / Q000601:surgery; D065289:Pedicle Screws; D012447:Sacrum / Q000000981:diagnostic imaging / Q000293:injuries* / Q000601:surgery; D016103:Spinal Fractures / Q000175:diagnosis / Q000601:surgery*