title: Opportunistic computed tomography screening shows a high incidence of osteoporosis in ankylosing spondylitis patients with acute vertebral fractures.
abstract: Advanced ankylosing spondylitis is associated with reductions in bone mineral density (BMD), contributing to pain and predisposing to fractures. Quantifying this reduction is complicated because overgrowth of bone and loss of trabecular bone occur concurrently. Traditional methods such as dual-energy X-ray absorptiometry struggle to generate accurate estimates of BMD in these patients. The aim of this study was to evaluate the utility of computed tomography (CT) attenuation in generating estimates of BMD in patients with severe AS who had sustained vertebral fractures. Patients with severe AS and bridging syndesmophytes who presented, with acute fractures of the spine, were reviewed to assess whether they had a CT scan in the 6 mo before or after injury that included an image of the L1 vertebra; if it did, the scans were selected for analysis. A total of 17 patients were evaluated. Using a CT attenuation threshold of 135 HU balanced for sensitivity and specificity, 14 of 17 (82%) patients were osteoporotic. Using a CT attenuation threshold for higher sensitivity (160 HU), 15 of 17 (88%) patients were osteoporotic. Even using the L1 CT attenuation threshold of 110 HU for higher specificity, 14 of 17 (82%) patients were osteoporotic. CT attenuation demonstrates that a high proportion of AS patients who sustain fractures have osteoporosis. This overcomes some of the difficulties that have been encountered with the use of dual-energy X-ray absorptiometry in this group of patients. This simple and accessible method saves on time, cost, and exposure to radiation and can help in the planning of a patient's management.
authors.affiliation: Department of Neurosurgery, Regions Hospital, St Paul, MN, USA. Electronic address: oemohare@umn.edu.
authors.forename: Osa
authors.initials: O
authors.lastname: Emohare
authors.affiliation: HealthPartners Institute for Education and Research, Bloomington, MN, USA.
authors.forename: Amanda
authors.initials: A
authors.lastname: Cagan
authors.affiliation: Department of Orthopaedic Surgery, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Polly
authors.affiliation: Section of Rheumatology, Regions Hospital, St Paul, MN, USA; Division of Rheumatology, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: Elie
authors.initials: E
authors.lastname: Gertner
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D015519:Bone Density; D018450:Disease Progression; D005260:Female; D005592:Fracture Fixation / Q000379:methods; D006801:Humans; D015994:Incidence; D008159:Lumbar Vertebrae / Q000293:injuries*; D008297:Male; D008501:Medical Records, Problem-Oriented; D008910:Minnesota; D010024:Osteoporosis / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology; D018579:Patient Selection; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D016103:Spinal Fractures / Q000000981:diagnostic imaging / Q000209:etiology / Q000601:surgery; D013167:Spondylitis, Ankylosing / Q000150:complications / Q000503:physiopathology; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Ankylosing spondylitis; CT attenuation; bone mineral density; fracture; osteoporosis; vertebral