TNFi Drugs May Be Bone-Builders in Ankylosing Spondylitis

Nigil Haroon N, Srignathan J, AlGhanim N, Inman R, Cheung AM. Effect of TNF-alpha inhibitor treatment on bone mineral density in patients with ankylosing spondylitis: a systematic review and meta-analysis.Semin Arth Rheum. (2014) Accepted Manuscript   vol 43. (Online before print)

Up to 62% of ankylosing spondylitis (AS) patients may be at risk for osteoporosis and fractures due to systemic inflammation partly fueled by tumor necrosis factor alpha (TNFα). This meta-analysis has suggested that not only can drugs which block TNFα prevent bone loss in AS, they may even build bone mineral density (BMD) over time.

The systematic literature review by a team at the University of Toronto, the first to assess the effect of TNFα inhibitors on bone, found that they improve BMD in the lumbar spine and total hip, as well as maintaining bone density in the femoral neck of AS patients for up to two years.

The meta-analysis also found that lumbar spine BMD improved significantly after a year of TNF treatment, by 5%, and with a further increase of 8.6% after two years, compared to bone density at baseline. Total hip BMD also increased over two years.

BMD in the femoral neck remained stable.

However, lack of data prevented a head-to-head comparison between controls and those given TNF-blockers.

In addition to reducing inflammation, and thereby reducing bone resorption, the researchers say that TNF drugs foster changes in body fat and muscles and improve quality of life, enabling AS patients to be more active, which can also strengthen bone.

Bone loss in AS patients is generally treated conservatively and with anti-resorptive drugs. The latter can be problematic, because since these relatively young patients will require long-term use of the drugs entailing risks of atypical femoral fractures and threatening the fetus if taken during pregnancy.