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Femoral Bone Mineral Density Is Associated with Vertebral Fractures in Patients with Ankylosing Spondylitis: A Cross-sectional Study
JAE-BUM JUN, KYUNG-BIN JOO, MIN-YOUNG HER, TAE-HWAN KIM, SANG-CHEOL BAE, DAE-HYUN YOO, and SEONG-KYU KIM ABSTRACT. Objective. To determine the association between vertebral fractures and clinical, laboratory, and radiological variables in patients with ankylosing spondylitis (AS). Methods. Sixty-eight men with AS and 91 sex- and age-matched controls were consecutively enrolled. Vertebral fractures were assessed according to a visual semiquantitative grading system using plain radiographs of the lumbar spine obtained from patients with AS. Disease activity variables including C-reactive protein, erythrocyte sedimentation rate, finger-to-ground distance score, Schober's Index score, Bath Ankylosing Spondylitis Radiology Index for the spine (BASRI-s) score, and syndesmophyte score were identified. Assessments of bone mineral density (BMD) of the lumbar spine and the femur in patients and controls were performed using an anteroposterior dual energy x-ray absorptiometry technique. Results. Eleven patients (16.2%) out of the total of 68 patients with AS had vertebral fractures; these were identified as wedge deformities (n = 5) or biconcave (n = 6) deformities. BMD levels of the lumbar spine and femur in patients were significantly reduced compared with those of age-matched controls. There were significant differences in the Schober's Index scores, finger-to-ground distance scores, BASRI scores of the lumbar spine, syndesmophyte scores, and intertrochanter values of BMD among AS patients both with and without vertebral fractures. Multiple logistic regression analyses revealed that intertrochanteric BMD values also were independently associated with vertebral fractures in AS (p = 0.041). Conclusion. We demonstrated evidence of a correlation between low femoral BMD levels and risk of vertebral fractures in patients with AS, especially at the intertrochanteric area. Longitudinal studies in a large population are required to determine the diagnostic implications of femur BMD for increased risk of vertebral fractures in AS. (J Rheumatol 2006;33:1637–41) Key Indexing Terms:
ANKYLOSING SPONDYLITIS From the Department of Rheumatology, The Hospital for Rheumatic Diseases, the Department of Diagnostic Radiology, Hanyang University, Seoul; and Division of Rheumatology, Department of Internal Medicine, College of Medicine, Dankook University, Cheonan, Chungcheong Nam Do, South Korea. Supported by a grant of the research fund of Hanyang University (HY-2002-S). J-B. Jun, MD, PhD, Associate Professor of Medicine, Department of Rheumatology, Hospital for Rheumatic Diseases; K-B. Joo, MD, PhD, Professor of Radiology, Department of Radiology, Hanyang University; M-Y. Her, MD, Clinical Fellow in Rheumatology; T-H. Kim, MD, PhD, Assistant Professor of Medicine; S-C. Bae, MD, PhD, MPH, Professor of Medicine; D-H. Yoo, MD, PhD, Professor of Medicine, Department of Rheumatology, Hospital for Rheumatic Diseases; S-K. Kim, MD, PhD, Assistant Professor of Medicine, Division of Rheumatology, Department of Internal Medicine, College of Medicine, Dankook University. Address reprint request to Dr. S-K. Kim, Division of Rheumatology, Department of Internal Medicine, College of Medicine, Dankook University, Cheonan, Chungcheong Nam Do, 330-715, South Korea. E-mail: kimsk714@empal.com Accepted for publication March 31, 2006.
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