title: Dynamic versus rigid stabilization for the treatment of disc degeneration in the lumbar spine.
abstract: METHODS
  Retrospective cohort study.
  
  
  OBJECTIVE
  This study aimed to describe the outcome of stabilization surgery with dynamic instrumentation for degenerative disc disease. The results were compared with age- and gender-matched peers treated with traditional fusion with rigid instrumentation. If necessary, additional nerve elements decompression was undertaken in both groups.
  
  
  METHODS
  This study analyzed the success rates of 25 patients aged 47.4 years (mean 95% confidence interval: 43.1-51.7) treated with stabilization of the involved vertebral dynamic unit(s) with either dynamic or rigid instrumentation with or without additional decompression. Clinical outcome was assessed with Oswestry disability index (ODI) and visual analogue scale (VAS) for back pain, leg pain, and activity level. Satisfaction outcome was measured with Stauffer and Coventry overall satisfaction criteria and VAS for satisfaction. Health-related quality of life was estimated with Short Form-36 (SF-36) questionnaires. Fusion rate and adjacent level(s) was checked with x-ray. Complications recorded in patients' files were evaluated and revision surgeries were stated as treatment failures.
  
  
  RESULTS
  At the 4-year follow-up (range, 2-5 years) significant improvement was noted on some subjective parameters in both groups. No statistical differences were seen between the groups at final follow-up. Five patients (42%) in the rigid group and two patients (20%) in the dynamic group were rated good or excellent according to the overall Stauffer and Coventry satisfaction criteria. Radiologically, seven patients (58%) in the rigid group were undoubtedly fused and all the involved discs in the dynamic group continued to degenerate. Adjacent segments showed loss of disc height in both groups but only loss of upper adjacent discs in the rigid group was statistically significant. Two patients in the dynamic group and one patient in the rigid group required reoperation because of the pedicle screw misplacement.
  
  
  CONCLUSIONS
  The results of this study indicate no significant difference between dynamic and rigid stabilization of the lumbar spine for patients with degenerative disc disease (DDD). However, the study is underpowered and further studies on larger and homogeneous group of patients should be undertaken. [Table: see text].
authors.affiliation: Department for Orthopaedic Surgery and Sports Trauma, Celje Teaching Hospital, Celje, Slovenia.
authors.forename: Samo K
authors.initials: SK
authors.lastname: Fokter
authors.forename: Andrej
authors.initials: A
authors.lastname: Strahovnik