Prevalent vertebral fractures incur high risk of future fractures in inflammatory myositis
OBJECTIVE To assess accrual of new vertebral fractures (VF) in patients with idiopathic inflammatory myositis (IIM) over a period of time.
METHODS Hundred patients who were previously enrolled for a cross-sectional study on prevalence of asymptomatic VF were telephonically requested to review with repeat spinal radiographs and dual-energy X-ray absorptiometry (DEXA) after 3 years. Radiographs were scored using Genant's semi-quantitative technique. Disease activity and damage were assessed by myositis damage index (MDI) extent of damage and modified MDI for which the osteoporotic fracture item in MDI was removed. VF progressors were compared with non-progressors.
RESULTS Of 31 patients reviewed, 11 had dermatomyositis, 8 polymyositis, and 6 each overlap and anti-synthetase syndrome. Eighteen patients underwent DEXA scan. Seventeen had VF at baseline. At 91.62 patient years of follow-up, total number of VF increased from 27 to 51. Patients who had previous VF had higher risk of developing a new VF when compared with those with no VF (76.5% vs. 14.28%, RR: 5.35). Patients with old VF accrue fractures at a rate of 26.2 per 100 patient years. The number of fractures correlated significantly with age, T scores at the L4 level, and lower third of radius on DEXA, MDI, and modified MDI. Neither conventional nor disease-related variables differed between progressors and non-progressors.
CONCLUSION Patients with IIM with a prior VF incurred a five times risk of subsequent VF irrespective of disease activity and glucocorticoids. Key Points • Patients with inflammatory myositis are at a high risk of asymptomatic vertebral fractures. • Patients with baseline vertebral fractures incur a high risk of future fractures on follow-up. • Number of fractures is negatively correlated with age, BMD values at lower end of radius, L4, and damage.