Determination of the modulus of elasticity of bone material by an acoustical approach at the forearm distinguishes women with and without vertebral fractures independent of bone mineral density.

Abstract

The modulus of elasticity is a parameter characterizing fracture stability of bone independent of bone mineral density. Measurement of acoustical properties of the forearm by determination of the resonant frequency of the ulna in longitudinal direction as a function of sound transmission velocity after adjustment of the measuring result by ulna length yields information about the modulus of elasticity. It was the aim of this study to investigate whether this parameter may distinguish between subjects with and without vertebral fractures independent of bone mineral density. Fifty females (61.1 +/- 9.1 years) were enrolled into the study, 25 with, and 25 age-matched without prevalent osteoporotic vertebral fracture(s). Especially low bone mineral density was not considered an exclusion criteria for enrollment into the control group. Resonant frequency of the ulna multiplied by ulna length was significantly lower in the group with prevalent fractures (53.6 +/- 6.8 m/s versus 56.8 +/- 5.2 m/s) after adjustment for age and after additional adjustment for forearm bone mineral density. Linear regression analysis showed complete independence of the acoustical parameter from bone mineral density. This study demonstrates that the modulus of elasticity of bone material is an independent risk factor for osteoporotic fractures. Acoustical measurement at the forearm by analyzing the resonant frequency of the ulna and correcting it by ulna length as geometrical parameter is capable of determining the modulus of elasticity in vivo.