title: Biomechanical effects of the extent of sacrectomy on the stability of lumbo-iliac reconstruction using iliac screw techniques: What level of sacrectomy requires the bilateral dual iliac screw technique?
abstract: BACKGROUND
  Although both single and dual iliac screw techniques are used in spino-pelvic reconstruction following sacrectomy for treating sacral tumors, the basis for choosing between the two techniques for different instability types remains undetermined. The purpose of this study was to evaluate the effects of the extent of sacrectomy on the stability of the lumbo-iliac fixation construct using single and dual iliac screw techniques.
  
  
  METHODS
  Nine human L2-pelvic specimens were tested for their intact condition simulated by L3-L5 pedicle screw fixation. Sequential partial sacrectomies and L3-iliac fixation using bilateral single and dual iliac screws were conducted on the same specimens as follows: under-S1 sacrectomy+single screw, under-½S1 sacrectomy+single screw, one-side sacroiliac joint resection+single screw, total sacrectomy+single screw, and total sacrectomy+dual screw. Biomechanical testing was performed on a material testing machine for evaluating the stiffness of the L3-iliac fixation construct in compression and torsion.
  
  
  RESULTS
  Single iliac screw technique was found to effectively restore the local stability in under-½S1 sacrectomy. However, it could not provide adequate stability for further resection of one-side sacroiliac joint in torsion and total sacrectomy in compression (P<0.05). On the other hand, dual iliac screw technique could restore the stability to the intact condition after total sacrectomy in both compression and torsion.
  
  
  CONCLUSIONS
  The single iliac screw technique for L3-iliac fixation could effectively restore the local stability for under-½S1 sacrectomy. However, for instabilities of the under-½S1 sacrectomy with one-side sacroiliac joint resection or total sacrectomy, the dual iliac screw technique should be considered.
authors.affiliation: Department of Spine Surgery, the First Affiliated Hospital of Sun Yat-sen University, 183 Huangpu East Road, Guangzhou, China, 510700. hpyubinsheng@hotmail.com
authors.forename: Bin-Sheng
authors.initials: BS
authors.lastname: Yu
authors.forename: Xin-Ming
authors.initials: XM
authors.lastname: Zhuang
authors.forename: Ze-Min
authors.initials: ZM
authors.lastname: Li
authors.forename: Zhao-Min
authors.initials: ZM
authors.lastname: Zheng
authors.forename: Zhi-Yu
authors.initials: ZY
authors.lastname: Zhou
authors.forename: Xue-Nong
authors.initials: XN
authors.lastname: Zou
authors.forename: William W
authors.initials: WW
authors.lastname: Lu
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D001863:Bone Screws; D005260:Female; D006801:Humans; D007085:Ilium / Q000601:surgery*; D016268:Internal Fixators; D008159:Lumbar Vertebrae / Q000601:surgery; D008297:Male; D008875:Middle Aged; D012446:Sacroiliac Joint / Q000601:surgery; D012447:Sacrum / Q000601:surgery; D013123:Spinal Fusion / Q000379:methods; D013314:Stress, Mechanical