title: Risk factors for adjacent segment disease development after lumbar fusion.
abstract: METHODS
  Retrospective cohort study.
  
  
  OBJECTIVE
  To identify factors which may be important in the occurrence of symptomatic adjacent segment disease (ASD) after lumbar fusion.
  
  
  BACKGROUND
  Many reports have been published about the risk factors for ASD after lumbar fusion. Despite on the great numbers of risk factors identified for ASD development, study results have been inconsistent and there is controversy regarding which are the most important.
  
  
  METHODS
  This study evaluated 120 patients who underwent 360° fusion lumbar surgery from 2007 to 2012. We separated the population into two groups: the first group included 60 patients with long lumbar fusion (three or more levels) and the second group included 60 patients with short lumbar fusion (less than three levels).
  
  
  RESULTS
  In the first group, symptomatic ASD was found in 19 cases during the one year follow-up. There were 14 cases with sagittal imbalance and 5 cases at the incipient stage of disc degeneration according to the preoperative magnetic resonance imaging. At the three year follow-up, symptomatic ASD was diagnosed in 31 cases, of which 17 patients had postoperative sagittal balance disturbance. In the second group, 10 patients had ASD at the one year follow-up. Among these cases, preoperative disc degenerative changes were identified in 8 patients. Sagittal imbalance was found only in 2 cases with symptomatic ASD at the one year follow-up. At the three year follow-up, the number of patients with symptomatic ASD increased to 14. Among them, 13 patients had initial preoperative adjacent disc degenerative changes.
  
  
  CONCLUSIONS
  Patients with postoperative sagittal imbalance have a statistically significant increased risk of developing symptomatic ASD due to an overloading the adjacent segments and limited compensatory capacities due to the large number of fixed mobile segments. In the case of a short fixation, preoperative degenerative changes are more important factors in the development of ASD.
authors.affiliation: Vreden Russian Research Institute of Traumatology and Orthopedics, Saint-Petersburg, Russia.
authors.forename: Sergei
authors.initials: S
authors.lastname: Masevnin
authors.affiliation: Vreden Russian Research Institute of Traumatology and Orthopedics, Saint-Petersburg, Russia.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Ptashnikov
authors.affiliation: Vreden Russian Research Institute of Traumatology and Orthopedics, Saint-Petersburg, Russia.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Michaylov
authors.affiliation: Vreden Russian Research Institute of Traumatology and Orthopedics, Saint-Petersburg, Russia.
authors.forename: Hao
authors.initials: H
authors.lastname: Meng
authors.affiliation: Vreden Russian Research Institute of Traumatology and Orthopedics, Saint-Petersburg, Russia.
authors.forename: Oleg
authors.initials: O
authors.lastname: Smekalenkov
authors.affiliation: Vreden Russian Research Institute of Traumatology and Orthopedics, Saint-Petersburg, Russia.
authors.forename: Nikita
authors.initials: N
authors.lastname: Zaborovskii
keywords: Adjacent segment disease; Fusion; Sagittal balance