Applied Kinesiology Laboratory, Program in Physical Therapy, Washington University School of Medicine, Campus Box 8502, 4444 Forest Park Blvd, Saint Louis, MO 63108 USA.
J Biomech. 2013 Feb 22;46(4):745-50. doi: 10.1016/j.jbiomech.2012.11.019. Epub 2012 Dec 6.
We investigated the capacity of bone quantity and bone geometric strength indices to predict ultimate force in the human second metatarsal (Met2) and third metatarsal (Met3). Intact lower extremity cadaver samples were measured using clinical, volumetric quantitative computed tomography (vQCT) with positioning and parameters applicable to in vivo scanning. During processing, raw voxel data (0.4mm isotropic voxels) were converted from Hounsfield units to apparent bone mineral density (BMD) using hydroxyapatite calibration phantoms to allow direct volumetric assessment of whole-bone and subregional metatarsal BMD. Voxel data were realigned to produce cross-sectional slices perpendicular to the longitudinal axes of the metatarsals. Average mid-diaphyseal BMD, bone thickness, and buckling ratio were measured using an optimized threshold to distinguish bone from non-bone material. Minimum and maximum moments of inertia and section moduli were measured in the mid-diaphysis region using both a binary threshold for areal, unit-density measures and a novel technique for density-weighted measures. BMD and geometric strength indices were strongly correlated to ultimate force measured by ex vivo 3-point bending. Geometric indices were more highly correlated to ultimate force than was BMD; bone thickness and density-weighted minimum section modulus had the highest individual correlations to ultimate force. Density-weighted geometric indices explained more variance than their binary analogs. Multiple regression analyses defined models that predicted 85-89% of variance in ultimate force in Met2 and Met3 using bone thickness and minimum section modulus in the mid-diaphysis. These results have implications for future in vivo imaging to non-invasively assess bone strength and metatarsal fracture risk.
我们研究了骨量和骨几何强度指数预测人类第二跖骨（Met2）和第三跖骨（Met3）极限力的能力。使用临床、体积定量计算机断层扫描（vQCT）对完整的下肢尸体样本进行测量，其定位和参数适用于体内扫描。在处理过程中，使用羟基磷灰石校准体模将原始体素数据（0.4mm 各向同性体素）从 Hounsfield 单位转换为表观骨矿物质密度（BMD），以允许对整个骨骼和跖骨亚区 BMD 进行直接体积评估。体素数据被重新对齐，以产生与跖骨纵轴垂直的横截面切片。使用优化的阈值测量平均中干骺端 BMD、骨厚度和弯曲比，以区分骨与非骨材料。使用二进制阈值进行面积、单位密度测量和用于密度加权测量的新方法，在中干骺端区域测量最小和最大惯性矩和截面模数。BMD 和几何强度指数与通过体外三点弯曲测量的极限力强烈相关。几何指数与极限力的相关性高于 BMD；骨厚度和密度加权最小截面模数与极限力的个体相关性最高。密度加权几何指数比其二进制对应物解释了更多的方差。多元回归分析定义了使用中干骺端骨厚度和最小截面模数预测 Met2 和 Met3 极限力 85-89%方差的模型。这些结果对未来的非侵入性活体成像评估骨骼强度和跖骨骨折风险具有重要意义。
