Clinical Risk Factors Associated With Vertebral Fractures in AS

Patients with ankylosing spondylitis (AS) frequently present with radiographic vertebral fractures, a risk that is more pronounced with older patients, baseline low bone mineral density (BMD), and those with advanced disease. Wedge shaped fractures, clustered in the thoracolumbar region, were most frequently noted. These results from a large observational study were recently published in Arthritis Care & Research.

Fiona Maas, MD, PhD, Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, the Netherlands, and colleagues conducted a prospective, longitudinal, observational, cohort study of patients enrolled in the Groningen Leeuwarden Ankylosing Spondylitis (GLAS) cohort between November 2004 and December 2012, who had available lateral radiographs of the thoracic and lumbar spine at baseline and 2-year follow-up. Radiographs were scored for vertebral fractures by 2 readers blinded to patient characteristics and disease status.

Two hundred ninety two patients with AS fulfilling the modified New York criteria were included in the study; 20% showed radiographic vertebral fractures at baseline, 5% developed new fractures, and 2% showed an increase in severity of existing fractures during the 2 year follow-up period. Fractures were generally mild and located in the mid-thoracic and thoracolumbar region of the spine.

“The presence of vertebral fractures was significantly associated with older age, higher BMI, longer smoking duration, larger occiput-to-wall distance, more spinal radiographic damage, and lower hip BMD,” said Dr Maas. “The development of new or progressive vertebral fractures was also associated with older age and low BMD.”

The researchers found that NSAID at baseline was independently associated with a decreased risk (odds ratio [OR[ 0.33, 95% CI: 0.14-0.76) of vertebral fractures at baseline.  These results were compatible with a previous case-control study of 758 patients with AS also found a decreased risk of fracture in patients taking NSAIDs.

Summary and Clinical Applicability

Data from a prospective longitudinal observational cohort study showed that radiographic vertebral fractures are frequently occurring in patients with AS.

“Vertebral fractures can easily be missed due to lack of symptoms or poor recognition on radiographs…[thus] imaging is important during follow-up, especially in older AS patients with more advanced disease, low BMD, and a less healthy lifestyle including smoking and high BMI,” the authors concluded.

Limitations and Disclosures

The researchers did not have data available on patients’ history of falls, dietary calcium intake, and physical activity, limiting their ability to relate the study data to the presence and development of vertebral fractures in the AS cohort.

Additionally, it was not possible to evaluate the differences between treatment strategies or to perform multivariable logistic regression analysis on the development of new vertebral fractures, as a small number of patients developed new fractures during the 2-year follow-up period.

Reference

Maas F, Spoorenberg A, van der Slik BPG, van der Veer E, et al. Clinical risk factors for the presence and development of vertebral fractures in patients with ankylosing spondylitis. Arthrit Care Res. 2016; doi: 10.1002/acr.22980 [Epub ahead of print]