title: Radiologic assessment of all unfused lumbar segments 7.5 years after instrumented posterior spinal fusion.
abstract: METHODS
  Prospective observational single-cohort study.
  
  
  OBJECTIVE
  To analyze long-term radiographic changes in all unfused lumbar segments after instrumented posterolateral lumbar fusion.
  
  
  BACKGROUND
  Adjacent segment degeneration (ASD) after lumbar fusion may be a consequence of biomechanical stress or result from constitutional factors. Most studies analyzing ASD only investigate the motion segments immediately above and below the fusion. None compares adjacent segments to all the other unfused segments after instrumented posterior fusion.
  
  
  METHODS
  Using the distortion-compensated roentgen analysis method, disc height, dorsoventral displacement, and lordosis were measured in 212 unfused segments from 62 patients, on digitized standing radiographs taken before fusion surgery and after a mean follow-up of 7.5 years (range, 4-11 years). The effect of covariables, such as age, length of follow-up, fusion level, number of fused segments, and sagittal and spinopelvic parameters on the preoperative to follow-up changes, were analyzed using a repeated-measurement model.
  
  
  RESULTS
  No changes were observed at the segments located below the fusion. All the unfused segments above the fusion showed the same significant loss of disc height. Loss of disc height did not depend on fusion parameters, correlated weakly with age and length of follow-up, and correlated highly across adjacent unfused segments.
  
  
  CONCLUSIONS
  After posterior lumbar instrumented fusion, radiographic changes suggesting disc degeneration appear homogeneously at several levels cephalad to fusion and seem to be determined by individual characteristics.
authors.affiliation: Unitat d'estudi de la Patología del Raquis, Hospital Universitari Vall d'Hebron, Barcelona, Spain. 24361fpu@comb.es
authors.forename: Ferran
authors.initials: F
authors.lastname: Pellisé
authors.forename: Alejandro
authors.initials: A
authors.lastname: Hernández
authors.forename: Xavier
authors.initials: X
authors.lastname: Vidal
authors.forename: Joan
authors.initials: J
authors.lastname: Minguell
authors.forename: Cristobal
authors.initials: C
authors.lastname: Martínez
authors.forename: Carlos
authors.initials: C
authors.lastname: Villanueva
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging*; D008141:Lordosis / Q000000981:diagnostic imaging / Q000601:surgery; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011859:Radiography; D016059:Range of Motion, Articular; D013122:Spinal Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D013123:Spinal Fusion / Q000009:adverse effects; D013997:Time Factors; D016896:Treatment Outcome