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RESEARCH PRODUCT

In-vivo investigation of material quality of bone tissue by measuring apparent phalangeal ultrasound transmission velocity

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The square of ultrasound transmission velocity in a material is related to the modulus of elasticity, which is known to be an indicator of stability in bone. The aim of our study was to use ultrasound transmission velocity to obtain information about the material properties of bone tissue, keeping other factors possibly influencing ultrasound transmission as constant as possible. Apparent phalangeal ultrasound transmission velocity (APU) measured in 54 isolated, fresh pig phalanges was shown to be independent of bone mineral density (BMD) measured by SPA. Fastest sound transmission led exclusively through cortical bone so that intertrabecular connectivity in spongious bone could not influence the result. In humans APU was measured in the mediolateral direction at the midphalanx of the middle finger. In 53 healthy subjects (15–81 years old; 27 women, 26 men), there was a decrease of APU with age (r=−0.30, p<0.05). Further, when comparing the results of both hands intraindividually almost identical values indicated constant intraindividual architecture of bone at this location. There was no evidence for a relation of APU to physical load comparing dominant and nondominant hand and relating the results to subjectively estimated physical load. In a second group of 43 perimenopausal women (47–60 years old), APU, which again decreased with age (r=−0.33, p<0.05), was found not be correlated to BMD measured by SPA at the distal forearm (cortical bone). In a third group of 40 women (17–78 years old), APU again decreased with age (r=−0.60, p<0.001) and was not correlated to BMD measured by SPA at the midphalanx of the middle finger, i.e. the same measuring location as APU. We conclude that this method provides information about the modulus of elasticity of bone with negligible influence of bone mineral density. Our results indicate that there is a deterioration of bone material quality with age independent of decreasing bone mineral density.