title: Cement augmentation versus extended dorsal instrumentation in the treatment of osteoporotic vertebral fractures: a biomechanical comparison.
abstract: OBJECTIVE
  Loosening of pedicle screws is a major complication of posterior spinal stabilisation, especially in the osteoporotic spine. Our aim was to evaluate the effect of cement augmentation compared with extended dorsal instrumentation on the stability of posterior spinal fixation.
  
  
  METHODS
  A total of 12 osteoporotic human cadaveric spines (T11-L3) were randomised by bone mineral density into two groups and instrumented with pedicle screws: group I (SHORT) separated T12 or L2 and group II (EXTENDED) specimen consisting of T11/12 to L2/3. Screws were augmented with cement unilaterally in each vertebra. Fatigue testing was performed using a cranial-caudal sinusoidal, cyclic (1.0 Hz) load with stepwise increasing peak force.
  
  
  RESULTS
  Augmentation showed no significant increase in the mean cycles to failure and fatigue force (SHORT p = 0.067; EXTENDED p = 0.239). Extending the instrumentation resulted in a significantly increased number of cycles to failure and a significantly higher fatigue force compared with the SHORT instrumentation (EXTENDED non-augmented + 76%, p < 0.001; EXTENDED augmented + 87%, p < 0.001).
  
  
  CONCLUSIONS
  The stabilising effect of cement augmentation of pedicle screws might not be as beneficial as expected from biomechanical pull-out tests. Lengthening the dorsal instrumentation results in a much higher increase of stability during fatigue testing in the osteoporotic spine compared with cement augmentation. Cite this article: Bone Joint J 2016;98-B:1099-1105.
authors.affiliation: University Medical Center Göttingen, Göttingen, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Weiser
authors.affiliation: University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Dreimann
authors.affiliation: Institute of Biomechanics, TUHH Hamburg University of Technology, Hamburg, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Huber
authors.affiliation: Institute of Biomechanics, TUHH Hamburg University of Technology, Hamburg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Sellenschloh
authors.affiliation: Institute of Forensic Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Püschel
authors.affiliation: Institute of Biomechanics, TUHH Hamburg University of Technology, Hamburg, Germany.
authors.forename: M M
authors.initials: MM
authors.lastname: Morlock
authors.affiliation: University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: J M
authors.initials: JM
authors.lastname: Rueger
authors.affiliation: University Medical Center Göttingen, Göttingen, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Lehmann
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D001843:Bone Cements / Q000627:therapeutic use*; D001863:Bone Screws; D002102:Cadaver; D002484:Cementation / Q000379:methods; D005260:Female; D015775:Fractures, Stress / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000517:prevention & control; D008297:Male; D058866:Osteoporotic Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D011475:Prosthesis Failure; D011897:Random Allocation; D016103:Spinal Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed
chemical_list: D001843:Bone Cements
keywords: Cement augmentation; Dorsal instrumentation; Instrumentation length; Pedicle screw; Spine biomechanics