Sierpowska J, Lammi M J, Hakulinen M A, Jurvelin J S, Lappalainen R, Töyräs J
Department of Physics, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio, Finland.
Med Eng Phys. 2007 Oct;29(8):845-52. doi: 10.1016/j.medengphy.2006.09.007. Epub 2006 Nov 13.
Mechanical properties of bone are determined not only by bone mineral density (BMD), but also by tissue trabecular structure and organic composition. Impedance spectroscopy has shown potential to diagnose trabecular bone BMD and strength, however, the relationships between organic composition and electrical and dielectric properties have not been systematically investigated. To investigate these issues organic composition of 26 human trabecular bone samples harvested from the distal femur and proximal tibia was determined and compared with relative permittivity, loss factor, conductivity, phase angle, specific impedance and dissipation factor measured at wide range (50 Hz to 5 MHz) of frequencies. A strong linear correlation was found between the relative permittivity at 1.2 MHz and trabecular bone fat content (r = -0.85, p<0.01, n=26). On the other hand, relative permittivity measured at 200 Hz served as a good predictor of water content (r = 0.83). Phase angle, specific impedance and especially conductivity were strongly related to the trabecular bone dry density and water content (|r| > or = 0.69). Variation in bone tissue collagen content was strongly related to the relative permittivity measured at 1.2 MHz (r = 0.64), but only moderately to other parameters. Glycosaminoglycan content showed no significant relations with any investigated electrical parameters. The present study indicates that if the trabecular bone composition is known, the relationships presented in this study could facilitate calculation of current field distribution, e.g. during electrical stimulation of osteogenesis. On the other hand, our results suggest that permittivity measured at low (<1 kHz) or high (>100 kHz) frequencies could be used, e.g. during implant surgery, for prediction of trabecular bone water or fat contents, respectively.
骨骼的力学性能不仅取决于骨矿物质密度（BMD），还取决于组织小梁结构和有机成分。阻抗谱已显示出诊断小梁骨BMD和强度的潜力，然而，有机成分与电学和介电性能之间的关系尚未得到系统研究。为了研究这些问题，测定了从股骨远端和胫骨近端采集的26个人小梁骨样本的有机成分，并将其与在宽频率范围（50Hz至5MHz）下测量的相对介电常数、损耗因子、电导率、相角、比阻抗和耗散因子进行比较。发现在1.2MHz时的相对介电常数与小梁骨脂肪含量之间存在强线性相关性（r = -0.85，p<0.01，n = 26）。另一方面，在200Hz时测量的相对介电常数可作为含水量的良好预测指标（r = 0.83）。相角、比阻抗，尤其是电导率与小梁骨干密度和含水量密切相关（|r|≥0.69）。骨组织胶原蛋白含量的变化与在1.2MHz时测量的相对介电常数密切相关（r = 0.64），但与其他参数的相关性仅为中等。糖胺聚糖含量与任何研究的电学参数均无显著关系。本研究表明，如果已知小梁骨成分，本研究中呈现的关系可有助于计算电流场分布，例如在骨生成的电刺激过程中。另一方面，我们的结果表明，在低频（<1kHz）或高频（>100kHz）下测量的介电常数可分别用于，例如在植入手术期间，预测小梁骨的水或脂肪含量。
