RISK OF VERTEBRAL FRACTURES IN MEN - RELATIONSHIP TO MINERAL DENSITY OF THE VERTEBRAL BODY

OBJECTIVE. Vertebral fracture is the most frequent manifestation of os teoporosis in women. Because there is a lack of information about bone density and the occurrence of fractures in men with osteoporosis, we evaluated the relationship between vertebral fractures and spinal bone mineral density (BMD) to determine if there is a threshold of BMD bel ow which fractures are likely to occur. SUBJECTS AND METHODS. Radiogra phs of the spine and BMD measurements of the lumbar spine as measured by quantitative CT were obtained in 201 men 21-86 years old (mean age, 68 +/- 4 years) who were referred consecutively for osteoporosis scre ening. Radiographs were interpreted for the presence or absence of ver tebral fractures. The probability of fractures was determined after cl assifying the patients into subgroups according to their quantitative CT values, The relationship of spinal bone mass to spinal fracture was examined by both logistic regression and receiver operating character istic (ROC) analysis. RESULTS. Seventy-one patients were classified as having definite vertebral compression fractures. Spinal BMD was 132 /- 34 mg/ml for the 130 men without Vertebral fractures and 75 +/- 22 mg/ml for the 71 men with vertebral fractures (p < .001), The number o f fractures per patient and the BMD were negatively correlated (r = -0 .71, p < 0.0001), When a BMD of 100 mg/ml was given as a fracture thre shold, 15% of the patients without fractures were below this value and 14% of the patients with fractures were above this threshold, Quantif ying the overlap between values from patients with and without fractur es by ROC analysis, the value of 100 mg/ml gave a sensitivity of 86%. Logistic regression showed 105 mg/ml as the most discriminate value, r esulting in a sensitivity of 90%. Logistic regression analysis of the predicted fracture probability also indicated that age does not signif icantly influence the regression curve. CONCLUSION. We found that dire ct quantitative CT measurement of the BMD of the vertebral body is a h ighly efficient approach to distinguish men without vertebral fracture s from those with fractures, Thus, a fracture-threshold concept could provide a quantitative criterion to identify men at high risk for vert ebral fractures.