title: Association between advanced degenerative changes of the atlanto-dens joint and presence of dens fracture.
abstract: BACKGROUND
  Dens fractures in elderly patients are often related to issues associated with aging. We examined the association between degenerative changes of the atlanto-dens joint and the risk of dens fracture.
  
  
  METHODS
  We conducted a retrospective study of trauma patients, fifty-five years of age or older, who had undergone a computed tomography scan of the cervical spine as part of their admission to a single level-I trauma center. There were 1794 patients who met the inclusion criteria; scans were evaluated for all fifty-six who presented with a dens fracture and for a random sample of 736 without a dens fracture. Intraosseous cyst formation, synovitis, and joint space narrowing were recorded from the scans. The prevalence of degenerative changes was compared between patients with and patients without a dens fracture.
  
  
  RESULTS
  An intraosseous cyst in the dens was found in 16.4% of the patients without a dens fracture and in 64.3% of those with a fracture (p < 0.001). The dens fracture extended through the existing cyst in twenty-four (66.7%) of thirty-six patients with a cyst and a dens fracture. Retro-dens synovitis was present in 4.2% of the patients without a dens fracture and 25.0% of those with a fracture (p < 0.001). After adjustment for age and sex, both cysts (odds ratio [OR] = 7.7, 95% confidence interval [CI] = 4.2 to 14.1) and synovitis (OR = 4.6, 95% CI = 2.1 to 10.0) were significantly associated with dens fracture.
  
  
  CONCLUSIONS
  Intraosseous dens cysts and retro-dens synovitis were associated with dens fracture; those with a dens fracture were nearly eightfold more likely to have an intraosseous cyst and nearly fivefold more likely to have synovitis compared with those without a dens fracture. Because the atlanto-dens joint is a synovial joint, its degeneration can lead to subchondral cyst formation and synovitis and predispose affected individuals to fracture.
authors.affiliation: Department of Orthopaedics and Rehabilitation, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, OP 31, Portland, OR 97239. E-mail address for J.U. Yoo: yooj@ohsu.edu.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Shinseki
authors.affiliation: Department of Orthopaedics and Rehabilitation, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, OP 31, Portland, OR 97239. E-mail address for J.U. Yoo: yooj@ohsu.edu.
authors.forename: Natalie L
authors.initials: NL
authors.lastname: Zusman
authors.affiliation: Department of Orthopaedics and Rehabilitation, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, OP 31, Portland, OR 97239. E-mail address for J.U. Yoo: yooj@ohsu.edu.
authors.forename: Jayme
authors.initials: J
authors.lastname: Hiratzka
authors.affiliation: Department of Orthopaedics and Rehabilitation, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, OP 31, Portland, OR 97239. E-mail address for J.U. Yoo: yooj@ohsu.edu.
authors.forename: Lynn M
authors.initials: LM
authors.lastname: Marshall
authors.affiliation: Department of Orthopaedics and Rehabilitation, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, OP 31, Portland, OR 97239. E-mail address for J.U. Yoo: yooj@ohsu.edu.
authors.forename: Jung U
authors.initials: JU
authors.lastname: Yoo
mesh_terms: D000058:Accidental Falls; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001268:Atlanto-Axial Joint / Q000473:pathology*; D001845:Bone Cysts / Q000150:complications / Q000473:pathology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009809:Odontoid Process / Q000293:injuries* / Q000473:pathology; D012189:Retrospective Studies; D017678:Sex Distribution; D016103:Spinal Fractures / Q000209:etiology* / Q000473:pathology; D013585:Synovitis / Q000150:complications / Q000473:pathology; D014057:Tomography, X-Ray Computed