title: [Instant and fatigue stability analysis of anterior lumbar interbody fusion with stand-alone cage].
abstract: OBJECTIVE
  To investigate the spinal segment instant and fatigue stability of anterior lumbar interbody fusion with stand-alone cage.
  
  
  METHODS
  The vertebrae L4 and S1 of 6 human lumbar specimens (L3 - S1) were embedded with dental base acrylic resin powder and fixed on mechanical machine, and the L4/L5 and L5/S1 disk spaces were left active. The 6 specimens underwent mechanical test as control group first, and then used as experimental group with a cage implanted in L5/S1. Instant instability was tested in three directions: flexion, extension, and lateral bend. The relative movement of L4/L5 and L5/S1 was recorded. Fatigue instability was tested after 50 000 times of flexion-extension movement, and the relative displacement between the cage and S1 was recorded.
  
  
  RESULTS
  In the three directions of flexion, extension, and lateral bend, the relative movements of L5/S1 in the experimental group were 0. 83 +/- 0.26 degrees, 1.60 +/- 0.19 degrees, and 0.72 +/- 0.20 degrees respectively, all significantly decreased than those of the control group (3.60 +/- 0.30 degrees, 4.82 +/- 0.34 degrees, and 3.80 +/- 0.28 degrees respectively, all P < 0.01). The relative movement of L4/L5 of the experimental group were 5.82 +/- 0.36 degrees, 5.38 +/- 0.30 degrees, and 4.96 +/- 0.29 degrees in the three directions respectively, all significantly higher than those of the control group (4.16 +/- 0.33 degrees, 4.02 +/- 0.30 degrees, and 3.48 +/- 0.34 degrees respectively, all P <0.01). After 50 000 times of flexion-extension fatigue movement, the relative displacement between the cage and S1 was zero.
  
  
  CONCLUSIONS
  Anterior lumbar interbody fusion with a stand-alone cage has excellent instant and fatigue stability, which can provide enough stability for clinical bone fusion without other internal fixation.
authors.affiliation: Department of Spinal Surgery, Tianjin Hospital, Tianjin 300211, China. mj6688@163.com
authors.forename: Jun
authors.initials: J
authors.lastname: Miao
authors.forename: Qun
authors.initials: Q
authors.lastname: Xia
authors.forename: Ji-Dong
authors.initials: JD
authors.lastname: Zhang
authors.forename: Shu-Jie
authors.initials: SJ
authors.lastname: Tan
authors.forename: Xue-Lian
authors.initials: XL
authors.lastname: Qin
authors.forename: Qi-Jin
authors.initials: QJ
authors.lastname: Feng
mesh_terms: D001696:Biomechanical Phenomena; D005221:Fatigue / Q000503:physiopathology; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods