[Bone mineral measurement of the calcaneus by single X-ray absorptiometry]

The bone mineral content (BMC) of the calcaneus was evaluated using single X-ray absorptiometry (SXA) with respect to reproducibility of bone mineral measurement, age-related bone loss in healthy Japanese, the spine fracture threshold in osteoporotic women, and the effect of non-weight bearing on bone mass in patients after hip arthroplasty. The mean reproducibilities using this method in vitro and in vivo were 0.81% and 0.59%. In 264 healthy men aged between 21 and 79 years and 328 healthy women aged between 20 and 79 years, the calcaneus BMC reached a peak in their twenties and thereafter decreased linearly with age by 0.57% per year in men and 1.32% per year in women. Body height and weight were well correlated with the calcaneus BMC in healthy men and women (p < 0.001). The bone mineral density (BMD) of the lumbar spine was measured using dual X-ray absorptiometry (DXA) and was significantly correlated with the calcaneus BMC in both men (r = 0.727, p < 0.001) and women (r = 0.703, p < 0.001). The fracture threshold, defined as the 90th percentile for calcaneus BMC in a woman with a vertebral fracture, was 313.31 mg/cm2 and 70.2% of the peak bone mass in the calcaneus. In 30 patients with hip implant arthroplasty, the bone mass in the calcaneus, lumbar spine and the distal radius was evaluated longitudinally during a follow-up period of one year. Only the calcaneus BMC in the treated leg changed significantly during this period. In the first four months, the calcaneus BMC in the treated leg diminished by approximately 21%, but had recovered by one year after surgery. We concluded that bone mineral measurement in the calcaneus was useful for evaluating age-related bone mass changes in healthy men and women, bone loss in osteoporotic patients, and the effect of non-weight bearing on bone mass in patients after hip arthroplasty.