title: Adjacent segment disease perspective and review of the literature.
abstract: BACKGROUND
  Adjacent segment disease has become a common topic in spine surgery circles because of the significant increase in fusion surgery in recent years and the development of motion preservation technologies that theoretically should lead to a decrease in this pathology. The purpose of this review is to organize the evidence available in the current literature on this subject.
  
  
  METHODS
  FOR THIS LITERATURE REVIEW, A SEARCH WAS CONDUCTED IN PUBMED WITH THE FOLLOWING KEYWORDS: adjacent segment degeneration and disease. Selection, review, and analysis of the literature were completed according to level of evidence.
  
  
  RESULTS
  The PubMed search identified 850 articles, from which 41 articles were selected and reviewed. The incidence of adjacent segment disease in the cervical spine is close to 3% without a significant statistical difference between surgical techniques (fusion vs arthroplasty). Authors report the incidence of adjacent segment disease in the lumbar spine to range from 2% to 14%. Damage to the posterior ligamentous complex and sagittal imbalances are important risk factors for both degeneration and disease.
  
  
  CONCLUSIONS
  Insufficient evidence exists at this point to support the idea that total disc arthroplasty is superior to fusion procedures in minimizing the incidence of adjacent segment disease. The etiology is most likely multifactorial but it is becoming abundantly clear that adjacent segment disease is not caused by motion segment fusion alone. Fusion plus the presence of abnormal end-fusion alignment appears to be a major factor in creating end-fusion stresses that result in adjacent segment degeneration and subsequent disease. The data presented cast further doubt on previously established rationales for total disc arthroplasty, at least with regard to the effect of total disc arthroplasty on adjacent segment degeneration pathology.
authors.affiliation: Department of Neurosurgery, University of Puerto Rico, San Juan, Puerto Rico.
authors.forename: Fanor M
authors.initials: FM
authors.lastname: Saavedra-Pozo
authors.affiliation: Department of Neurosurgery, University of Brasília, Brasília, Brazil.
authors.forename: Renato A M
authors.initials: RA
authors.lastname: Deusdara
authors.affiliation: Department of Neurosurgery, Cleveland Clinic, Cleveland, OH.
authors.forename: Edward C
authors.initials: EC
authors.lastname: Benzel
keywords: Arthrodesis; arthroplasty; cervical vertebrae; intervertebral disc degeneration; lumbar vertebrae; spinal diseases; spinal fusion; total disc replacement