The dependence of ultrasonic properties on orientation in human vertebral bone

Abstract

Speed of sound (SOS) and broad-band ultrasound attenuation (BUA) were measured in cubes of human trabecular bone from lumbar vertebrae, in the three major anatomical axes. There were significant differences in sos and in BUA when measured in the different axes, indicating a structural component to the ultrasonic measurement. Qualitatively different behaviour was observed in the cranio-caudal (CC) axis compared to the transverse directions: SOS was approximately 500 m s(-1) greater than in either the lateral (LT) or antero-posterior (AP) axes, and BUA was approximately 23 dB MHz(-1) cm(-1) greater. Small, but significant, differences existed between the AP and LT axes for both SOS and BUA. In the AP and LT directions, strong linear correlations existed between sos and apparent density (r = 0.90), and between BUA and apparent density (r = 0.96). In the cc axis, correlations with density were poorer. The anomalous behaviour in the cc axis was due to a transient travelling ahead of the main wavefront, and it is suggested that this represents propagation of ultrasound directly through the trabecular framework as a bar wave. This can only occur in the cc axis where the majority of trabeculae are orientated parallel to the direction of propagation. Measurements on cubes in air, as opposed to water, supported this hypothesis. Modifications to the experimental technique necessary to consistently detect this phenomenon are described.

Speed of sound reflects Young’s modulus as assessed by microstructural finite element analysis

“…Other studies also reported similar results. 15,32,33,35 In the present study, SOS accounted for 84%-92% of the variance in FEA-estimated Young's modulus in each of the three perpendicular directions, and for 89% when the directions were pooled. In previous studies, the associations between stiffness and ultrasound velocity in human bone specimens were reported as r values between 0.44 and 0.77, 12,15,36 and r 2 values between 0.41 and 0.72.…”

“…4,14 Postmortem specimen studies have shown that ultrasound velocity is structure-related, as evidenced by its dependence on the measuring direction in bone cubes. 15,18,33,35,36 Furthermore, strong correlations between elastic moduli and ultimate strength, on the one hand, and ultrasound velocity, on the other, have been found in bovine 17,35,43 and human 5,12,15,17,36 trabecular bone samples. Recently, high-resolution microcomputed tomography (CT) reconstruction of trabecular bone was introduced.…”

Bone Quality Assessment by Quantitative Ultrasound of Proximal Phalanxes of the Hand in Healthy Subjects Aged 3–21 Years

“…The influence of cortical thickness on AD-SoS is suggested by recent data in vitro (20,21) showing that a reduction of cortical thickness was associated with a reduced AD-SoS. In addition, some studies in human vertebral (35,36) and in bovine radial or femoral (10, 37) bone specimens showed that QUS reflected some structural characteristics of trabecular bone mainly related to trabecular orientation. Wuster et al (13) showed similar results in human phalangeal bone.…”

Assessment of Bone Quality by Quantitative Ultrasound of Proximal Phalanges of the Hand and Fracture Rate in Children and Adolescents with Bone and Mineral Disorders

“…Furthermore, in humans it has been demonstrated that AD-SoS and relative CA, both measured at the ROI of the middle finger, were significantly correlated (r ϭ 0.74, p Ͻ 0.0001), with the relative CA estimated as CA/(CA ϩ MA) ratio, where CA and MA were assessed by magnetic resonance imaging (50). However, it has also been shown that the amount of trabecular bone in the phalanges of the hand reflects their actual mineral content (8), and that phalangeal QUS reflects bone density and structural changes of trabecular bone in bone specimens of human vertebrae (43,51) and of bovine and rat radius or femur (11,52,53). Similar results are reported in human phalangeal bone (54).…”