Biomechanical analysis of different types of pedicle screw augmentation: a cadaveric and synthetic bone sample study of instrumented vertebral specimens

Med Eng Phys. 2013 Oct;35(10):1506-12. doi: 10.1016/j.medengphy.2013.04.007. Epub 2013 May 11.


This study aims to determine the pull-out strength, stiffness and failure pull-out energy of cement-augmented, cannulated-fenestrated pedicle screws in an osteoporotic cadaveric thoracolumbar model, and to determine, using synthetic bone samples, the extraction torques of screws pre-filled with cement and those with cement injected through perforations. Radiographs and bone mineral density measurements from 32 fresh thoracolumbar vertebrae were used to define specimen quality. Axial pull-out strength of screws was determined through mechanical testing. Mechanical pull-out strength, stiffness and energy-to-failure ratio were recorded for cement-augmented and non-cement-augmented screws. Synthetic bone simulating a human spinal bone with severe osteoporosis was used to measure the maximum extraction torque. The pull-out strength and stiffness-to-failure ratio of cement pre-filled and cement-injected screws were significantly higher than the non-cement-augmented control group. However, the cement pre-filled and cement-injected groups did not differ significantly across these values (p=0.07). The cement pre-filled group had the highest failure pull-out energy, approximately 2.8 times greater than that of the cement-injected (p<0.001), and approximately 11.5 times greater than that of the control groups (p<0.001). In the axial pull-out test, the cement-injected group had a greater maximum extraction torque than the cement pre-filled group, but was statistically insignificant (p=0.17). The initial fixation strength of cannulated screws pre-filled with cement is similar to that of cannulated screws injected with cement through perforations. This comparable strength, along with the heightened pull-out energy and reduced extraction torque, indicates that pedicle screws pre-filled with cement are superior for bone fixation over pedicle screws injected with cement.

Keywords: Bone screw; Dimensions; Insertion; Performance requirements; Pull-out; Static; Test methods; Torsion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Biomechanical Phenomena
  • Bone Cements
  • Bone Screws*
  • Cadaver
  • Humans
  • Materials Testing*
  • Mechanical Phenomena*
  • Middle Aged
  • Orthopedic Procedures / instrumentation*
  • Osteoporosis / surgery
  • Spine*
  • Torque


  • Bone Cements