title: The Biomechanical Properties of Pedicle Screw Fixation Combined With Trajectory Bone Cement Augmentation in Osteoporotic Vertebrae.
abstract: METHODS
  The biomechanics of pedicle screw fixation combined with trajectory cement augmentation with various filling volumes were measured by pull-out, periodic antibending, and compression fatigue tests.
  
  
  OBJECTIVE
  To investigate the biomechanical properties of the pedicle screw fixation combined with trajectory bone cement (polymethylmethacrylate) augmentation in osteoporotic vertebrae and to explore the optimum filling volume of the bone cement.
  
  
  BACKGROUND
  Pedicle screw fixation is considered to be the most effective posterior fixation method. The decrease of the bone mineral density apparently increases the fixation failure risk caused by screw loosening and displacement. Trajectory bone cement augmentation has been confirmed to be an effective method to increase the bone intensity and could markedly increase the stability of the fixation interface.
  
  
  METHODS
  Sixteen elderly cadaveric 1-5 lumbar vertebral specimens were diagnosed with osteoporosis. The left and right vertebral pedicles were alternatively randomized for treatment in all groups, with the contralateral pedicles as control. The study groups included: group A (pedicle screw fixation with full trajectory bone cement augmentation), group B (75% filling), group C (50% filling), and group D (25% filling). Finally, the bone cement leakage and dispersion were assessed and the mechanical testing was conducted.
  
  
  RESULTS
  The bone cement was well dispersed around the pedicle screw. The augmented bone intensity, pull-out strength, periodic loading times, and compression fatigue performance were markedly higher than those of the control groups. With the increase in trajectory bone cement, the leakage was also increased (P<0.05). The pull-out strength of the pedicle screw was increased with an increase in bone mineral density and trajectory bone cement. It peaked at 75% filling, with the largest power consumption.
  
  
  CONCLUSIONS
  The optimal filling volume of the bone cement was 75% of the trajectory volume (about 1.03 mL). The use of excessive bone cement did not increase the fixation intensity but increased the risk of leakage.
authors.affiliation: *Department of Orthopedics, the First Affiliated Hospital of Anhui Medical University, Anhui†Institute of Shanghai Biological Mechanics Engineering Research, Shanghai University, Shanghai, China.
authors.forename: Haitao T
authors.initials: HT
authors.lastname: Fan
authors.forename: Renjie J
authors.initials: RJ
authors.lastname: Zhang
authors.forename: Cailiang L
authors.initials: CL
authors.lastname: Shen
authors.forename: Fulong L
authors.initials: FL
authors.lastname: Dong
authors.forename: Yong
authors.initials: Y
authors.lastname: Li
authors.forename: Peiwen W
authors.initials: PW
authors.lastname: Song
authors.forename: Chen
authors.initials: C
authors.lastname: Gong
authors.forename: Yijin J
authors.initials: YJ
authors.lastname: Wang
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena / Q000187:drug effects; D001843:Bone Cements / Q000494:pharmacology*; D015519:Bone Density / Q000187:drug effects; D019245:Compressive Strength / Q000187:drug effects; D005260:Female; D005592:Fracture Fixation; D006801:Humans; D008159:Lumbar Vertebrae / Q000187:drug effects / Q000601:surgery*; D008297:Male; D010024:Osteoporosis / Q000503:physiopathology* / Q000601:surgery*; D065289:Pedicle Screws
chemical_list: D001843:Bone Cements