Osteoporosis and associated fractures have become increasingly common in Korea. We studied the bone mineral density (BMD) of the vertebral body using dual energy X-ray absorptiometry in a percutaneous vertebroplasty group and compared it with that in an osteoporotic group to investigate the correlations between BMD, age distribution and fracture site and to estimate the fracture threshold in the percutaneous vertebroplasty group.

We analyzed 32 patients who were older than 50 years and performed percutaneous vertebraoplasty due to osteoporotic compression fractures. Thoraco-lumbar and lumbo-sacral films were taken of all patients. Measurement of vertical height of the anterior, middle and posterior regions of the vertebrae was made on standard lateral radiographs of the spine. BMD of the lumbar spine was determined by dual energy x-ray absorptiometry (DEXA Lunar PRODIGY, GE system, Madison, Wis, USA).

Age related BMD changes decreased markedly between the sixth and seventh decades. BMD in the percutaneous vertebroplasty group was significantly lower than in the osteoporotic group. The osteoporotic compression fracture rate increased with age. A lower BMD showed a higher incidence of osteoporotic compression fracture. In the percutaneous vertebroplasty group, the 90th percentile of BMD was defined as the fracture threshold at 0.81 g/cm2. The 12th thoracic vertebrae and the 1st lumbar vertebrae were the most frequent fracture sites.

We conclude that when the BMD decreases to less than 0.81 g/cm2, the risk of osteoporotic compression fractures escalates rapidly. Postmenopausal women with BMDs lower than this fracture threshold should receive prophylaxes for osteoporotic fracture.