Total body, spine, and femur dual X-ray absorptiometry in spinal osteoporosis

The aim of this study was to evaluate the ability of dual x-ray absorptiometry (DXA) to discriminate between normal and osteoporotic patients. A total of 152 postmenopausal women entered the study: 73 (aged 61.2 +/- 8 years) had established postmenopausal osteoporosis with one or more vertebral crushes on lateral X-ray of spine, and 79 (aged 59.3 +/- 7.8 years) had no vertebral fractures. Measurements of bone mineral content (BMC) in grams, bone mineral density (BMD) in g/cm2 and body composition (lean and fat mass in grams) of total body, lumbar spine (L2-L4), and femur (neck, trochanter, Ward's triangle) were carried out with a LUNAR DPX densitometer. In all sites, BMD values of osteoporotic patients were significantly lower than those of the control subjects. The higher Z-score was found for total body density (-2.14) followed by L2-L4 (-2.0), femoral neck (-1.93), Ward's triangle (-1.69), and trochanter (-1.4). Only the trochanter Z-score was significantly different compared with the other sites. A fracture threshold was determined for each site from osteoporotic patients and normal controls: with a sensitivity set at 90%, the best specificity was obtained at the lumbar spine and total body sites (89% and 84%, respectively). BMD values were highly related to lean and fat body mass, but bone loss with age was unrelated to soft tissue change. In conclusion, BMD measurements at different skeletal sites enable detection of spinal osteoporosis although sensitivity for femoral areas was less with respect to total body and L2-L4 BMD values.