Prevalence of vertebral fractures in adults with cystic fibrosis and their relationship to bone mineral density

Abstract

Study objectives: The objectives of this study were to determine the prevalence of morphometric vertebral fractures in a large cohort of adult cystic fibrosis (CF) patients, and to examine the association between fractures and bone mineral density (BMD).

Design: Cross-sectional retrospective study.

Setting: A tertiary care academic hospital.

Patients: Adult CF patients who had undergone BMD testing and chest radiography within 1 month of each other.

Measurements and results: BMD was measured by dual-energy x-ray absorptiometry (DXA) at the lumbar spine (LS) and femoral neck (FN). Vertebral fractures were diagnosed using lateral chest radiographs. Several clinical and biochemical variables were assessed as correlates. Sixty subjects (36%) had z scores between -1.0 and -2.5, and 15 subjects (9%) had z scores of < -2.5. Twelve patients (7.2%) had 19 morphometric fractures. The mean BMD at the LS was 1.266 g/cm(2) in the fracture group and 1.112 g/cm(2) in the nonfracture group (p = 0.0002). The mean BMD at the FN was 1.129 g/cm(2) in the fracture group and 0.987 g/cm(2) in the nonfracture group (p = 0.0006). Both FEV(1) and body mass index were significantly associated with BMD at both the LS and the FN.

Conclusion: Seven percent of adult patients with CF had vertebral fractures as determined by morphometry. Subjects in the fracture group had both clinically and statistically higher BMD as measured by DXA. Our findings raise the intriguing possibility that BMD may not be useful in identifying CF patients with fractures.