title: Thoracic kyphosis and rate of incident vertebral fractures: the Fracture Intervention Trial.
abstract: CONCLUSIONS
  Biomechanical analyses support the theory that thoracic spine hyperkyphosis may increase risk of new vertebral fractures. While greater kyphosis was associated with an increased rate of incident vertebral fractures, our analysis does not show an independent association of kyphosis on incident fracture, after adjustment for prevalent vertebral fracture. Excessive kyphosis may still be a clinical marker for prevalent vertebral fracture.
  
  
  BACKGROUND
  Biomechanical analyses suggest hyperkyphosis may increase risk of incident vertebral fracture by increasing the load on vertebral bodies during daily activities. We propose to assess the association of kyphosis with incident radiographic vertebral fracture.
  
  
  METHODS
  We used data from the Fracture Intervention Trial among 3038 women 55-81 years of age with low bone mineral density (BMD). Baseline kyphosis angle was measured using a Debrunner kyphometer. Vertebral fractures were assessed at baseline and follow-up from lateral radiographs of the thoracic and lumbar spine. We used Poisson models to estimate the independent association of kyphosis with incident fracture, controlling for age and femoral neck BMD.
  
  
  RESULTS
  Mean baseline kyphosis was 48° (SD = 12) (range 7-83). At baseline, 962 (32%) participants had a prevalent fracture. There were 221 incident fractures over a median of 4 years. At baseline, prevalent fracture was associated with 3.7° greater average kyphosis (95% CI 2.8-4.6, p < 0.0005), adjusting for age and femoral neck BMD. Before adjusting for prevalent fracture, each 10° greater kyphosis was associated with 22% increase (95% CI 8-38%, p = 0.001) in annualized rate of new radiographic vertebral fracture, adjusting for age and femoral neck BMD. After additional adjustment for prevalent fracture, estimated increased annualized rate was attenuated and no longer significant, 8% per 10° kyphosis (95% CI -4 to 22%, p = 0.18).
  
  
  CONCLUSIONS
  While greater kyphosis increased the rate of incident vertebral fractures, our analysis does not show an independent association of kyphosis on incident fracture, after adjustment for prevalent vertebral fracture. Excessive kyphosis may still be a clinical marker for prevalent vertebral fracture.
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, School of Medicine, University of California, 1500 Owens Suite 400, San Francisco, CA, 94158, USA. wendy.katzman@ucsf.edu.
authors.forename: W B
authors.initials: WB
authors.lastname: Katzman
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, USA.
authors.forename: E
authors.initials: E
authors.lastname: Vittinghoff
authors.affiliation: Departments of Family and Preventive Medicine and Internal Medicine, University of California, San Diego, USA.|Department of Internal Medicine, University of California, Davis, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Kado
authors.affiliation: Department of Internal Medicine, University of California, Davis, USA.
authors.forename: N E
authors.initials: NE
authors.lastname: Lane
authors.affiliation: Minneapolis VA Health Care System, University of Minnesota, Minneapolis, USA.
authors.forename: K E
authors.initials: KE
authors.lastname: Ensrud
authors.affiliation: Division of Physical Therapy, Department of Community and Family Medicine, Duke University, Durham, USA.
authors.forename: K
authors.initials: K
authors.lastname: Shipp
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density / Q000502:physiology; D005260:Female; D005272:Femur Neck / Q000503:physiopathology; D006801:Humans; D015994:Incidence; D007738:Kyphosis / Q000150:complications* / Q000453:epidemiology / Q000473:pathology / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000293:injuries*; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000150:complications / Q000453:epidemiology / Q000503:physiopathology; D058866:Osteoporotic Fractures / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D015995:Prevalence; D012307:Risk Factors; D016103:Spinal Fractures / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D013904:Thoracic Vertebrae / Q000293:injuries*; D014481:United States / Q000453:epidemiology
keywords: Incidence; Kyphosis; Vertebral fracture