title: Biomechanical evaluation of supplemental percutaneous lumbo-sacro-iliac screws for spinopelvic fixation following total sacrectomy.
abstract: METHODS
  This is a cadaveric biomechanical study evaluating the biomechanical properties of a novel spinopelvic fixation technique with percutaneous lumbo-sacro-iliac (LSI) screws in an unstable total sacrectomy model.
  
  
  OBJECTIVE
  To compare standard posterior dual rod spinopelvic fixation alone with dual rod fixation supplemented with LSI screw fixation.
  
  
  BACKGROUND
  Primary or metastatic tumors of the sacrum requiring a total sacrectomy can result in spinopelvic instability if inadequate fixation is achieved. Many fixation techniques have been proposed to address this instability. However, to date, an optimal fixation technique has not been established.
  
  
  METHODS
  Ten fresh-frozen cadaveric spinopelvic specimens were randomized according to bone mineral density (BMD) to either posterior rod fixation (control group) or posterior rod fixation with supplemental LSI screws (LSI group). After fixation, a total sacrectomy of each specimen was performed. Specimens where then potted and axially loaded in a caudal direction. Stiffness, yield load, energy absorbed at yield load, ultimate load, and energy absorbed at ultimate load were computed. A Student t test was used for statistical analysis with significance set at P<0.05.
  
  
  RESULTS
  The average age and BMD were not significantly different between the control and LSI groups (age: P=0.255; BMD: P=0.810). After normalizing for BMD, there were no significant differences detected for any of the biomechanical parameters measured between the 2 fixation techniques: stiffness (P=0.857), yield load (P=0.219), energy at yield load (P=0.293), ultimate load (P=0.407), and energy at ultimate load (P=0.773). However, both fixation techniques were able to withstand physiological loads.
  
  
  CONCLUSIONS
  Our study did not demonstrate any biomechanical advantage for supplemental LSI screw fixation in our axial loading model. However, given the theoretical advantage of this percutaneous technique, further studies are warranted that take into account forward bending and sagittal stability.
authors.affiliation: *Department of Orthopaedic Surgery, University of California, Irvine, Orange †Department of Orthopaedic Surgery, University of Southern California, Los Angeles ‡Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System §NuVasive Inc., San Diego, CA.
authors.forename: Vu H
authors.initials: VH
authors.lastname: Le
authors.forename: Nathanael
authors.initials: N
authors.lastname: Heckmann
authors.forename: Nickul
authors.initials: N
authors.lastname: Jain
authors.forename: Lawrence
authors.initials: L
authors.lastname: Wang
authors.forename: Alexander W L
authors.initials: AW
authors.lastname: Turner
authors.forename: Thay Q
authors.initials: TQ
authors.lastname: Lee
authors.forename: S Samuel
authors.initials: SS
authors.lastname: Bederman
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D015519:Bone Density; D001863:Bone Screws / Q000009:adverse effects*; D002102:Cadaver; D005260:Female; D006801:Humans; D007085:Ilium / Q000601:surgery*; D008161:Lumbosacral Region / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009984:Orthopedic Fixation Devices / Q000009:adverse effects*; D019637:Orthopedic Procedures / Q000379:methods*; D012447:Sacrum / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods