REFLECTION ULTRASOUND VELOCITIES AND HISTOMORPHOMETRIC AND CONNECTIVITY ANALYSES - CORRELATIONS AND EFFECT OF SLOW-RELEASE SODIUM-FLUORIDE

To better understand how structural and functional bone properties con tribute to the changes in bone biomechanical properties revealed by ul trasound critical angle reflectometry (UCR) analysis, we measured both UCR velocities and histomorphometric properties in bone biopsy specim ens from 33 osteoporotic patients before and following intermittent sl ow-release sodium fluoride (SRNaF) and continuous calcium citrate admi nistration, Mean skeletal fluoride exposure was 17 months, and mean sk eletal fluoride content was 0.203 +/- 0.088 SD% bone ash, Intermittent SRNaF and continuous calcium citrate promoted significant increases i n trabecular thickness (122 +/- 18 SD mu m to 131 +/- 20, p = 0.020), mineral apposition rate (0.79 +/- 0.26 to 1.05 +/- 0.40 mu m/day,p = 0 .014), and a significant decline in eroded surface (3.9 +/- 1.6 to 2.8 +/- 1.4%, p = 0.002). There were also significant increases in node n umber (0.193 +/- 0.100 to 0.368 +/- 0.245, p < 0.01) and node-to-node strut length (0.076 +/- 0.087 to 0.191 +/- 0.173, p < 0.01) relative t o total cancellous area, Cortical UCR velocity did not change but canc ellous velocity significantly increased by 97 m/s following therapy (p = 0.0005), When compared against the significant changes in bone hist omorphometry and connectivity, the sum of both cancellous and cortical ultrasound velocities was significantly correlated with node number/a rea (R-2 = 0.305, p < 0.0001) and node-to-node strut length/area (R-2 0.372, p < 0.0001) and to a lesser extent with mineral apposition rate (R-2 = 0.106, p = 0.032), Multiple regression analysis demonstrated t hat 40% of the variance in the sum of the UCR velocities can be accoun ted for by the variability in these histomorphometric and connectivity parameters, There were no significant correlations between the sum of cortical and cancellous ultrasound velocities and cancellous bone vol ume (R-2 = 0.014 p 0.533), trabecular thickness (R-2 = 0.012, p = 0.47 ), or bone mineral density (R-2 = 0.003, p = 0.80). These observations indicate that velocity measurements with the UCR methodology show an improvement in bone elasticity associated, in part, with an improvemen t in the rate of bone mineralization and an improvement in bone qualit y at the structural level as shown by microarchitecture.