title: A novel anchoring system for use in a nonfusion scoliosis correction device.
abstract: BACKGROUND
  Insertion of a pedicle screw in the mid- and high thoracic regions has a serious risk of facet joint damage. Because flexible implant systems require intact facet joints, we developed an enhanced fixation that is less destructive to spinal structures. The XSFIX is a posterior fixation system that uses cables that are attached to the transverse processes of a vertebra.
  
  
  OBJECTIVE
  To determine whether a fixation to the transverse process using the XSFIX is strong enough to withstand the loads applied by the XSLATOR (a novel, highly flexible nonfusion implant system) and thus, whether it is a suitable alternative for pedicle screw fixation.
  
  
  METHODS
  The strength of a novel fixation system using transverse process cables was determined and compared with the strength of a similar fixation using polyaxial pedicle screws on different vertebral levels.
  
  
  METHODS
  Each of the 58 vertebrae, isolated from four adult human cadavers, was instrumented with either a pedicle screw anchor (PSA) system or a prototype of the XSFIX. The PSA consisted of two polyaxial pedicle screws and a 5 mm diameter rod. The XSFIX prototype consisted of two bodies that were fixed to the transverse processes, interconnected with a similar rod. Each fixation system was subjected to a lateral or an axial torque.
  
  
  RESULTS
  The PSA demonstrated fixation strength in lateral loading and torsion higher than required for use in the XSLATOR. The XSFIX demonstrated high enough fixation strength (in both lateral loading and torsion), only in the high and midthoracic regions (T10-T12).
  
  
  CONCLUSIONS
  This experiment showed that the fixation strength of XSFIX is sufficient for use with the XSLATOR only in mid- and high thoracic regions. For the low thoracic and lumbar region, the PSA is a more rigid fixation. Because the performance of the new fixation system appears to be favorable in the high and midthoracic regions, a clinical study is the next challenge.
authors.affiliation: Department of Mechanical Engineering, Laboratory of Biomechanical Engineering, University of Twente, Faculty of Engineering Technology, Drienerlolaan 5, PO Box 217, 7500 AE Enschede, The Netherlands. Electronic address: m.wessels@utwente.nl.
authors.forename: Martijn
authors.initials: M
authors.lastname: Wessels
authors.affiliation: Department of Mechanical Engineering, Laboratory of Biomechanical Engineering, University of Twente, Faculty of Engineering Technology, Drienerlolaan 5, PO Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Jasper J
authors.initials: JJ
authors.lastname: Homminga
authors.affiliation: Department of Mechanical Engineering, Laboratory of Biomechanical Engineering, University of Twente, Faculty of Engineering Technology, Drienerlolaan 5, PO Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Edsko E G
authors.initials: EE
authors.lastname: Hekman
authors.affiliation: Department of Mechanical Engineering, Laboratory of Biomechanical Engineering, University of Twente, Faculty of Engineering Technology, Drienerlolaan 5, PO Box 217, 7500 AE Enschede, The Netherlands; Department of Rehabilitation Medicine, University Medical Center Groningen, University of Groningen, Hanzeplein 1, Faculty of Medical Sciences, PO Box 30.001, 9700 RB Groningen, The Netherlands.
authors.forename: Gijsbertus J
authors.initials: GJ
authors.lastname: Verkerke
mesh_terms: D000369:Aged, 80 and over; D006801:Humans; D016268:Internal Fixators; D008159:Lumbar Vertebrae / Q000601:surgery*; D019637:Orthopedic Procedures / Q000295:instrumentation*; D065289:Pedicle Screws; D012600:Scoliosis / Q000601:surgery*; D013904:Thoracic Vertebrae / Q000601:surgery*
keywords: Anchor; Cable; Pedicle screw; Posterior; Scoliosis; Transverse process