ULTRASOUND BONE DENSITOMETRY OF THE OS CALCIS IN JAPANESE WOMEN

The velocity (SOS), attenuation slope (BUA) and stiffness index in the os calcis were measured using the 'Achilles' ultrasound bone densitometer (Lunar, Madison, WI). We evaluated the basic attributes of this ultrasound bone densitometer, and showed the age-related changes in ultrasound values in normal Japanese women. The precision was measured in vivo on ten occasions over a 2-week period in 5 subjects. The short-term precision errors (CVs) in vivo were 0.6% for stiffness index, 0.3% for SOS and 1.0% for BUA. Spine, femur neck and total body BMD using dual X-ray absorptiometry (DXA) were highly correlated with stiffness index (r=0.80, 0.77 and 0.78, respectively) in 194 subjects. Ultrasound values for patients with osteoporosis were significantly lower than those for the normal controls. The Z-score compared with young normals was significantly higher for spine bone mineral density (-4.4) than for stiffness index (-3.5); BUA and SOS gave significantly lower Z-scores -2.9 and -3.0, respectively). Ultrasound values were also lower compared with age-matched normal controls. The Z-score for stiffness index (-2.1) was significantly superior to that for either SOS or BUA (-1.5). Age-related change in ultrasound values was evaluated in 842 normal women. There was a decline in stiffness index of about 24% from the values in young adulthood to those of women in their seventies, about 75% of which occurred from age 44-49 years onward. These findings seem to indicate that the menopause affected the change in ultrasound values. In conclusion, ultrasound bone densitometry may not be as useful as DXA of the spine for screening for osteoporosis, since the Z-score for DXA is excellent. However, ultrasound bone densitometry appears potentially to be applicable to problems in the diagnosis and management of osteoporosis when used in association with DXA.