title: Computer simulation and image guidance for individualised dynamic spinal stabilization.
abstract: OBJECTIVE
  Dynamic implants for the human spine are used to re-establish regular segmental motion. However, the results have often been unsatisfactory and complications such as screw loosening are common. Individualisation of appliances and precision implantation are needed to improve the outcome of this procedure. Computer simulation, virtual implant optimisation and image guidance were used to improve the technique.
  
  
  METHODS
  A human lumbar spine computer model was developed using multi-body simulation software. The model simulates spinal motion under load and degenerative changes. After virtual degeneration of a L4/5 segment, virtual pedicle screw-based implants were introduced. The implants' positions and properties were iteratively optimised. The resulting implant positions were used as operative plan for image guidance and finally implemented in a physical spine model.
  
  
  RESULTS
  In the simulation, the introduction and optimisation of virtually designed dynamic implants could partly compensate for the effects of virtual lumbar segment degeneration. The optimised operative plan was exported to two different image-guidance systems for transfer to a physical spine model.
  
  
  CONCLUSIONS
  Three-dimensional computer graphic simulation is a feasible means to develop operative plans for dynamic spinal stabilization. These operative plans can be transferred to commercially available image-guidance systems for use in implantation of physical implants in a spine model. This concept has important potential in the design of operative plans and implants for individualised dynamic spine stabilization surgery.
authors.affiliation: Department of Neurosurgery, University Medical Centre, Johannes Gutenberg-University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany, nchi@gmx.de.
authors.forename: S R
authors.initials: SR
authors.lastname: Kantelhardt
authors.forename: U
authors.initials: U
authors.lastname: Hausen
authors.forename: M
authors.initials: M
authors.lastname: Kosterhon
authors.forename: A N
authors.initials: AN
authors.lastname: Amr
authors.forename: K
authors.initials: K
authors.lastname: Gruber
authors.forename: A
authors.initials: A
authors.lastname: Giese
mesh_terms: D001863:Bone Screws; D003198:Computer Simulation; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008962:Models, Theoretical; D013123:Spinal Fusion / Q000379:methods*