DO ULTRASOUND MEASUREMENTS ON THE OS CALCIS REFLECT MORE THE BONE MICROARCHITECTURE THAN THE BONE MASS - A 2-DIMENSIONAL HISTOMORPHOMETRIC STUDY

Few studies have analyzed the relationship between ultrasound measurem ents (US) and corresponding histomorphometric parameters of the calcan eus. To address this question we have compared US and histomorphometri c parameters in 17 whole human os calcis from amputation or necropsy, Speed of sound (SOS), broadband ultrasound attenuation (BUA), and bone mineral density (BMD) were measured on the whole foot at the calcanea l site using an Achilles(R) device and a DPX-L(R) densitometer (Lunar) . The os calcis was dissected and a 1-cm-wide transcortical parallelep iped extracted with a biopsy needle, focused on the center of the meas ured area. Histomorphometry was performed on undecalcified biopsies. S tructural and connectivity parameters were measured on 7-mu m-thick se ctions with both automatic (Biocom) and semiautomatic analyzers (Ibas 1(R), Kontron). We found that all ultrasonic and densitometric paramet ers reflected the true amount of bone and were correlated with only so me of the parameters reflecting bone microarchitecture, From stepwise regression analysis, we found that 68%, 67%, 72%, and 74% of the varia nce of SOS, BUA stiffness, and BMD, respectively, were explained signi ficantly by trabeculae thickness only. Ultrasonic measurements appear to reflect bone quantity rather than bone microarchitecture. The curre nt conclusion is fairly negative with respect to the ability of ultras ound to assess structural parameters, but our limited sample size did not give enough power to our study to reach statistically significant correlations. In addition, the calcaneus is anisotropic and the ultras ound interaction in bone is a three-dimensional phenomenon. So, a thre e-dimensional study rather than a two-dimensional one should be perfor med.