What Is the Best Site for Assessing Bone Loss in Ankylosing Spondylitis?

According to the results of a 5-year study published in Arthritis Research & Therapy, the best site at which to assess bone loss in patients with ankylosing spondylitis (AS) is the femoral neck. Results also indicate that medication use, including bisphosphonates and tumor necrosis factor inhibitors (TNFi) may have a positive impact on bone mineral density (BMD).

Investigators sought to explore BMD changes after 5 years at different measuring sites in patients with AS and to evaluate disease-related variables and medication use as predictors of BMD changes in these individuals. BMD was measured with the use of dual-energy x-ray absorptiometry at the hip, lumbar spine anterior-posterior (AP) and lateral projections, and total radius, both at baseline and again after 5 years. 

All participants were evaluated by means of questionnaires, blood samples, and spinal radiographs to grade AS-linked alterations in the spine with the modified Stoke Ankylosing Spondylitis Spinal Score.

A total of 204 patients were enrolled at baseline, with 162 (82%; 76 women and 92 men) undergoing reexamination at 5 years. Significant BMD decreases were noted at the femoral neck and radius, and increases were noted at the lumbar spine for both AP and lateral projections (P <.001 for both). 

Mean C-reactive protein level at 5-year follow-up was predictive of a significant decrease in femoral neck BMD (change in percent, β = –0.15; P =.046).

The use of bisphosphonates was predictive of a significant increase in BMD at all measured sites (P <.001 to P <.013), other than the total radius. The use of TNFi predicted a significant increase in AP spinal BMD (β = 3.15; P =.012).

The investigators noted that BMD increases in lumbar AP and lateral projections “might be influenced by osteoproliferation,” and suggested that the femoral neck may be the best site for assessment of bone loss in patients with AS. Additionally, results indicate that both bisphosphonates and TNFi have positive impacts on BMD in AS.

Disclosures: Dr Lorentzon reports receiving lecturing fees from Amgen, Meda, Rehnapharma, and Lilly and consulting fees from Radius Health. Dr Geijer reports receiving advisory board and lecturing fees from Novartis. Dr Jacobsson reports receiving advisory board fees from Novartis, Celgene, and MSD. Dr Forsblad-d’Elia reports receiving advisor board fees from Sandoz and Novartis, as well as an unrestricted grant from Novartis.

Reference

Deminger A, Klingberg E, Lorentzon M, et al. Which measuring site in ankylosing spondylitis is best to detect bone loss and what predicts the decline: results from a 5-year prospective study. Arthritis Res Ther. 2017;19(1):273.