Ultrasound velocity and broadband attenuation as predictors of load-bearing capacities of human calcanei

Abstract

The main purpose of this study was to determine whether calcaneal ultrasound parameters, measured in the mediolateral direction, reflect load-bearing capacities of human calcanei. Broadband ultrasound attenuation (BUA) and ultrasound velocity (UV) were measured in 20 cadaveric calcanei with a mean age of 74.1 (SD 8.8). Normalized BUA (nBUA) was determined by dividing BUA by the calcaneal thickness obtained using a pulse-echo technique. The bone mineral density (BMD) of each calcaneus was measured by quantitative computed tomography. The calcanei were embedded in PMMA to simulate the midstance physiologic orientation during compressive testing in the load-bearing direction. The failure load, stiffness, and energy absorption were determined for each calcaneus. It was shown that BMD was well correlated with all ultrasound parameters (P < 0.0001). BMD, BUA, nBUA, and UV were all significantly associated with calcaneal failure load, stiffness, and energy absorption capacity (P < 0.05). nBUA was found to be the strongest predictor of all compressive properties. BUA and BMD demonstrated similar predictability of stiffness and energy absorption capacity, however, BUA showed a more significant relationship to the failure load of the calcaneus than did BMD. UV was found to be inferior to BMD, as well as BUA or nBUA, in assessing failure load, stiffness, and energy absorption capacity. It was also shown that nBUA was superior to BUA in the assessment of load-bearing capacity, but not in the prediction of BMD. Multivariate regression analysis showed that the combination of BUA or nBUA with UV did not improve the predictability of failure load, stiffness, and energy absorption capacity over that of BUA or nBUA alone (P > 0.5).

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

“…These studies differed also with respect to location and type of trabecular bone used (human calcaneal, lumbar spine or femoral neck bone samples, 5,12,15,36 bovine femoral bone samples, 35 or both human and bovine samples, 17 ), the preparation and size of the bone samples, and the ultrasound system used, so it is difficult to compare the results with our study. Nevertheless, it seems evident that the associations between SOS and stiffness, estimated by FEA in the present study, are stronger than the associations reported in the studies in which stiffness was assessed by mechanical testing.…”

“…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. 5,17 In the bovine model, r 2 values of between 0.79 and 0.83 have been reported.…”

“…These associations are similar to those reported by others. 3,5,12,15,17,19,23,35,36 Because density is a scalar quantity, which cannot account for anisotropy, different relationships between Young's modulus and SOS, on the one hand, and BMD, on the other, are bound to be found in the different directions. This also explains the weaker association between BMD and Young's modulus when the directions were pooled.…”

“…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.…”

Acoustic shadowing from neuraxial bone

“…However, the combination of tramadol and metoclopramide may increase sedation compared with tramadol alone [4], and it is possible that the synergistic sedative effect of tramadol and metoclopramide contributed to our patient's respiratory depression.…”