The diagnostic validity of local and total bone mineral measurements in postmenopausal osteoporosis and osteoarthritis.

Assessment of different forms of prevention and treatment of bone mineral loss depends upon valid and precise methods to assess bone mass. We have here studied four groups of women: 45 healthy premenopausal women, 37 healthy postmenopausal women, 21 women with osteoarthritis and 20 with hip fractures. Bone mass was measured in the spine and total body by dual photon absorptiometry and in two forearm sites (proximal and distal bone mineral content (BMC) by single photon absorptiometry. The long-term (1 year) reproducibility was 1.2% for proximal BMC, 1.6% for distal BMC, 5.5% for spinal BMC, and 2.1% for total body bone mass (TBBM). In the early postmenopausal years bone mass was mainly reduced in areas with a high content of trabecular bone. In elderly postmenopausal women and women with hip fractures bone mass was almost identical in all four sites studied. The osteoarthritic patients had an 18% reduction of bone mass in the forearms and in TBBM, whereas the spinal bone mass was only reduced by 6%. In all subgroups TBBM could be predicted from the forearm measurements with standard errors of estimates of 9-13%. When the osteoarthritic women were excluded spinal bone mass could be predicted from both forearm measurements with a standard error of 15% (r = 0.74). The distal forearm BMC seems to be a more accurate estimate of spinal bone mass than does the proximal measurement. Of the 20 patients with hip fracture 16 had a distal forearm value below the premenopausal normal range, whereas spinal bone mass was subnormal in only eight (P less than 0.05). We conclude that bone loss is universal in patients with hip fracture and measurements of forearm bone mass will meet most clinical and research demands.