title: Comparison of three posterior dynamic stabilization devices.
abstract: METHODS
  A biomechanical study using human cadaveric lumbar spinal motion segments and three different posterior stabilization devices.
  
  
  OBJECTIVE
  To compare the range of motion, disc height, and foraminal area of a spinal motion segment intact, injured, and fixed with each of three posterior lumbar motion preservation devices.
  
  
  BACKGROUND
  Motion-sparing lumbar posterior dynamic stabilization devices are gaining increasing popularity, particularly for the treatment of degenerative disc disease.
  
  
  METHODS
  The PercuDyn, the X-Stop, and the Isobar posterior stabilization devices were compared using an in vitro cadaveric model. First, pure moments of ±8 Nm were applied in all three planes, then a follower load of 700 N was applied, and finally, sagittal bending tests were repeated. All tests were conducted using an 8-df servohydraulic load frame. Experiments were performed intact, with a simulated injury, and then with each of the three devices for a total of four specimens per device. Foraminal area and disc height (posterolateral and anterior surface) were measured under neutral and peak torques in all three planes and range of motion was recorded for all experimental conditions.
  
  
  RESULTS
  Overall, the injury model successfully increased range of motion and decreased disc height and foraminal area. Once treated with one of the three implants, the PercuDyn was most effective at preventing hyperextension, decreasing extension with a follower load by a mean of 52% compared to injured conditions (P = 0.07). The X-Stop stabilized the posterior column, increasing foraminal area under all conditions, particularly extension with a follower load, by 27% compared to injured conditions (P = 0.01). The Isobar, the only device to stabilize the anterior column, increased anterior disc height under flexion with a follower load by 22% (P = 0.03).
  
  
  CONCLUSIONS
  All three devices functioned as intended by their respective manufacturers, but each appeared to excel in different areas; therefore, each should be used for unique clinical applications.
authors.affiliation: Orthopaedic Research Center at Orthopaedic Hospital/University of California Los Angeles, Los Angeles, CA 90007, USA.
authors.forename: Sophia N
authors.initials: SN
authors.lastname: Sangiorgio
authors.forename: Hormoz
authors.initials: H
authors.lastname: Sheikh
authors.forename: Sean L
authors.initials: SL
authors.lastname: Borkowski
authors.forename: Larry
authors.initials: L
authors.lastname: Khoo
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Warren
authors.forename: Edward
authors.initials: E
authors.lastname: Ebramzadeh
mesh_terms: D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D007403:Intervertebral Disc / Q000033:anatomy & histology / Q000502:physiology / Q000601:surgery; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000502:physiology* / Q000601:surgery*; D008953:Models, Anatomic; D019736:Prostheses and Implants / Q000145:classification / Q000592:standards*; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods