Prevalence and predictors of asymptomatic vertebral fractures in inflammatory myositis

To assess the frequency and risk factors of asymptomatic vertebral fractures in inflammatory myositis.

Dorsal and lumbar spine lateral radiographs were taken for adults with inflammatory myositis and scored using Genant's semi-quantitative technique. Demographic data, weight, height, postmenopausal status, duration of corticosteroid use, drug intake, co-morbidities and past history of fractures were recorded. Bone mineral density (BMD) was assessed using dual-energy X-ray absorptiometry (DEXA). Myositis Damage Index (MDI) was also assessed. All results are expressed in median and interquartile range.

One hundred patients (82 female) with myositis of median age 35.5 (28.5-46) years and disease duration 3.0 (1.81-8.0) years were studied. Thirty-five patients had adult dermatomyositis (DM), 26 polymyositis, 31 connective tissue disease-associated myositis and eight had juvenile onset myositis. Seventeen were postmenopausal women. Forty-six patients had asymptomatic vertebral fractures and 19 had more than one fracture. Half the fractures occurred in those with disease duration of <5 years. Of the 69 fractures, 47 (68.1%), 16 (23.2%) and 6 (8.7%) were mild, moderate and severe, respectively. The 11th and 12th thoracic vertebrae were together the most commonly (30.4%) affected. Of the 70 who underwent BMD assessment, 62.7% were osteopenic and 26.9% were osteoporotic. T scores of DEXA scan at the lower third of the radius correlated negatively with fracture number (r = -0.27 (-0.50 to -0.005), P = 0.04). Gender, age, disease duration, years of corticosteroid intake, body mass index, years post-menopause and MDI had no correlation with number of fractures.

Patients with inflammatory myositis have high prevalence of asymptomatic vertebral fractures.