Bone mineral density improves during 2 years of treatment with bisphosphonates in patients with ankylosing spondylitis

To evaluate whether 2 years of treatment with bisphosphonates in combination with calcium/vitamin D supplements has an effect on lumbar spine and hip bone mineral density (BMD) in ankylosing spondylitis (AS) patients starting tumour necrosis factor-α inhibitors or receiving conventional treatment. Secondly, to explore the development of radiographic vertebral fractures.

Patients from the Groningen Leeuwarden AS cohort receiving bisphosphonates based on clinical indication and available 2-year follow-up BMD measurements were included. BMD of lumbar spine (L1-L4) and hip (total proximal femur) were measured using dual-energy X-ray absorptiometry. Spinal radiographs (Th4-L4) were scored for vertebral fractures according to the Genant method.

In the 20 included patients (median 52 years, 14 males), lumbar spine and hip BMD Z-scores increased significantly; median from -1.5 (interquartile range [IQR] -2.2 to 0.4) to 0.1 (IQR -1.5 to 1.0); P < .001 and median from -1.0 (IQR -1.6 to -0.7) to -0.8 (IQR -1.2 to 0.0); P = .006 over 2 years, respectively. In patients also treated with tumour necrosis factor-α inhibitors (n = 11), lumbar spine and hip BMD increased significantly (median 2-year change +8.6% [IQR 2.4 to 19.6; P = .009] and +3.6% [IQR 0.7-9.0; P = .007]). In patients on conventional treatment (n = 9), lumbar spine BMD increased significantly (median 2-year change +3.6%; IQR 0.7 to 9.0; P = .011) and no improvement was seen in hip BMD (median -0.6%; IQR -3.1 to 5.1; P = .61). Overall, younger AS males with limited spinal radiographic damage showed most improvement in lumbar spine BMD. Four mild radiographic vertebral fractures developed in 3 patients and 1 fracture increased from mild to moderate over 2 years in postmenopausal women and middle-aged men.

This explorative observational cohort study in AS showed that 2 years of treatment with bisphosphonates in combination with calcium/vitamin D supplements significantly improves lumbar spine BMD. Mild radiographic vertebral fractures still occurred.