title: Disc changes in the bridged and adjacent segments after Dynesys dynamic stabilization system after two years.
abstract: METHODS
  Prospective case series.
  
  
  OBJECTIVE
  To study the radiologic changes in the intervertebral disc after Dynesys dynamic stabilization.
  
  
  BACKGROUND
  Adjacent segment disc degeneration is one of the potential complications of fusion surgery. It has been proposed that nonfusion motion preservation surgery may prevent accelerated adjacent segment degeneration because of the protective effect of persisting segmental motion.
  
  
  METHODS
  Thirty-two patients who underwent Dynesys procedure between November 2002 and June 2004 and have completed 2-year follow-up MRI scans were included in this study. Preoperative and 2 year postoperative lumbar MRI scans were evaluated by 2 independent observers. T2-weighted mid-sagittal images were used and disc degeneration classified according to the Woodend classification of disc degeneration. Anterior and posterior intervertebral disc heights were also measured.
  
  
  RESULTS
  Of the 32 patients, 20 patients underwent Dynesys procedure alone and 12 underwent additional fusion at 1 or more levels. A total of 70 levels were operated on, of which 13 levels were fused.There was a statistically significant increase in the mean Woodend score at the operated levels in the Dynesys alone group, a change from 1.95 before surgery to 2.52 after surgery (P < 0.001). The mean Woodend scores changed from 1.27 preoperative to 1.55 postoperative (P = 0.066) at the proximal adjacent levels, and from 1.37 to 1.62 at the distal levels (P = 0.157). There was good interobserver agreement (weighted kappa score of 0.819). The anterior intervertebral disc height reduced by 2 mm from 9.25 to 7.17 (P < 0.001). The posterior disc height increased by 0.14 mm but this change was not significant.
  
  
  CONCLUSIONS
  Disc degeneration at the bridged and adjacent segment seems to continue despite Dynesys dynamic stabilization. This continuing degeneration could be due to natural disease progression.
authors.affiliation: Department of Orthopaedic Surgery, Woodend Hospital, Arberdeen, UK. drabhi.kp@gmail.com
authors.forename: Abhishek
authors.initials: A
authors.lastname: Kumar
authors.forename: James
authors.initials: J
authors.lastname: Beastall
authors.forename: Justin
authors.initials: J
authors.lastname: Hughes
authors.forename: Efthimios J
authors.initials: EJ
authors.lastname: Karadimas
authors.forename: Malcolm
authors.initials: M
authors.lastname: Nicol
authors.forename: Francis
authors.initials: F
authors.lastname: Smith
authors.forename: Douglas
authors.initials: D
authors.lastname: Wardlaw
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000209:etiology / Q000473:pathology*; D011446:Prospective Studies; D013122:Spinal Diseases / Q000473:pathology* / Q000601:surgery*; D013123:Spinal Fusion / Q000009:adverse effects / Q000379:methods*