Ankylosing Spondylitis and The Risk of Osteoporosis
Spine Community News: Ankylosing Spondylitis (AS) is an inflammatory arthritis of the spine usually associated with calcification of spinous structures, primarily the ligaments and facet joints. Although the calcification brings more calcium to the spine, this structure is more brittle and weakened. The inflammation of AS can cause loss of bone mineral density in vertebral bodies and hips. This loss of bone mineral density results in osteoporosis and increased risk of fractures. Osteoporosis is treatable, but should it be treated in patients who have excessive calcification?
A recent review suggests that osteoporosis should be treated in patients with AS. As many as 50% of AS screened patients. Many AS patients with OP are younger than the usual OP patient. The loss of bone is in the trabecular architecture of the vertebral body, the usual location for OP fractures. The risk for hip fractures in AS patients is not as clear.
Dual-energy x-ray absorptiometry (DXA) is the main method utilized for diagnosing osteoporosis. If the T-score is below -2.5, the patient has evidence of osteoporosis and treatment is recommended. One problem with usual spinal DXA is that syndesmophytes can artificially increase the presence of bone calcium in the spine leading to an under diagnosis of osteoporosis. OP may also be noted in the hip in 51% of AS patients. Those individuals with AS with C reactive protein elevations were at greater risk for OP.
There is a general consensus that AS patients with osteoporosis should be treated. Ankylosing Spondylitis patients should take an adequate amount of vitamin D with the goal of attaining a blood level of 34 or higher. If AS patients have osteoporosis they should take a 600 mg calcium supplement daily and should obtain additional dietary calcium. In addition weight-bearing exercise improve bone density and are recommended for all AS patients.
Bisphosphonates (alendronate, risedronate, ibandronate, zolendronic acid) are medications used to improve bone mineral density and reduce osteoporosis. These drugs have been studied for treatment of osteoporosis in patients with AS and have some benefit. Other therapies, like denusamab, and teraperitide, have not yes been studied in AS patients.
Tumor necrosis factor inhibitors (TNF) are recommended for the treatment of active AS in patients who have failed a least 2 nonsteroidal drugs and have an added benefit in that they increase bone mineral density but may not be adequate to reverse bone loss to normal levels.
All AS patients should have a DXA within a year of being diagnosed. If osteoporosis is present, AS patients should be treated with non-pharmacologic and pharmacologic therapy, primarily bisphosphonates. The use of TNF therapy should be based upon treating AS, not because of the potential benefits for increasing bone mineral density.
David Borenstein, MD
Executive Editor TheSpineCommunity.com
Reference: Hinze AM, Louie GH. Osteoporosis management in ankylosing spondylitis. Curr Treat Options in Rheum 2016;2:271-282