title: Comparisons of outcomes after single or multilevel dynamic stabilization: effects on adjacent segment.
abstract: METHODS
  A retrospective study.
  
  
  OBJECTIVE
  To compare the clinical/radiologic outcomes and effects on adjacent segments by Dynesys stabilization.
  
  
  BACKGROUND
  Dynamic stabilization is known to preserve some range of motion (ROM) and to lessen the load on adjacent levels compared with rigid fixation. However, there is concern about the stiffness of Dynesys. In a long-term follow-up study (>4 y), motion of Dynesys was preserved in only 8% of patients and adjacent segment degeneration occurred up to 47% of patients. Little information is available about the risk factor regarding adjacent segment motion.
  
  
  METHODS
  Twenty-one patients underwent lumbar spine stabilization with Dynesys owing to degenerative spinal disease (single, 7; multiple-level, 14). Clinical outcomes were evaluated using K-ODI, VAS, and MacNab criteria. Radiologic evaluations included whole spine AP/lateral, lumbar neutral, flexion, and extension x-ray. Follow-up period was 31±14 months. Single (group A) and multiple-level stabilization (group B, average 2.3 levels) were compared.
  
  
  RESULTS
  Clinical improvement was not different between the 2 groups (P>0.05). Sagittal balance, lumbar lordosis, ROM of the lumbar spine, pelvic tilt, and sacral slope were not changed postoperatively (P>0.05) in either group. Postoperatively, ROM of stabilized segments were significantly decreased from 12.8±4.8 degrees to 3.9±5 degrees, while ROM of segments above was increased in both groups (P<0.01). Disc height was not decreased in either group (P>0.05). However, retrolisthesis was observed on adjacent segments above in 6 patients only in group B, which may suggests adjacent segment problem.
  
  
  CONCLUSIONS
  Clinically, dynamic stabilization is a good alternative treatment option for degenerative spinal disease. However, dynamic stabilization preserves only limited motion and may cause stress on the adjacent level above. Adjacent segment disease may be closely monitored, especially in cases of multiple-levels dynamic stabilization.
authors.affiliation: Department of Neurosurgery, Seoul National University Hospital, South Korea.
authors.forename: Chi Heon
authors.initials: CH
authors.lastname: Kim
authors.forename: Chun Kee
authors.initials: CK
authors.lastname: Chung
authors.forename: Tae-Ahn
authors.initials: TA
authors.lastname: Jahng
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods*; D011859:Radiography; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D013122:Spinal Diseases / Q000000981:diagnostic imaging / Q000601:surgery*; D018709:Statistics, Nonparametric; D016896:Treatment Outcome