In vitro testing of a new transpedicular stabilization technique

M. Pfeiffer*, H. Hoffman, V. K. Goel, James Neil Weinstein, P. Griss

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


The rigidity of a pedicle screw implant is a critical biomechanical variable in lumbar spinal fusions. Sufficient rigidity is required for integration of bone grafts and to promote healing. Osteopenia, stress shielding, and compensatory hypermobility have been described as consequences of excessive rigidity. Little is known about the biomechanical characteristics of 'semirigid' compared to 'rigid' implants. A new implant, whose rigidity can be varied by selection of different implant components, was tested in vitro under well-defined loading conditions. The three- dimensional load-displacement behavior of all lumbar vertebrae involved in or adjacent to the two-level fusion was evaluated for two fusion modifications: bilateral rigid and bilateral semirigid. Cyclic fatigue loading was subsequently carried out under realistic conditions and motion testing repeated. The rigid device reduced the motion of the L3-4 transfixed segment in the primary movement planes by 87.3% with respect to the intact spine value in flexion/extension (FE), 86.3% in lateral bending (LB), and 76.8% in axial rotation (AR). The semirigid device achieved a reduction in motion of 79.6% (FE), 82.7% (LB), and 51.7% (AR). The semirigid implant was particularly easy to insert, because no bending of rods or plates was necessary. The implants showed no loosening or breakage after the fatigue testing. The results are compared to other available systems and the underlying biomechanics discussed.

Original languageEnglish (US)
Pages (from-to)249-255
Number of pages7
JournalEuropean Spine Journal
Issue number4
StatePublished - 1997


  • Biomechanics
  • Pedicle screw
  • Spinal fusion
  • Spine
  • Stress shielding

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine


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