Fractal dimension as a measure of altered trabecular bone in experimental inflammatory arthritis
Fractal dimension as a measure of altered trabecular bone in experimental inflammatory arthritis
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DOI：
10.1359/jbmr.1998.13.6.978
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发表时间：
1998-06-01
影响因子：
6.2
通讯作者：
Bogoch, ER
中科院分区：
文献类型：
--
作者：
Caldwell, CB;Moran, EL;Bogoch, ER
我们之前在实验性炎症性关节炎(EIA)和人类类风湿性关节炎(RA)中的研究表明，骨吸收和骨形成迅速重塑，增加了5倍。正常的髁状突骨小梁具有典型的各向异性，其方向沿应力线；病理状态下的快速重塑可能会扰乱正常的骨小梁排列顺序。这项研究评估了EIA诱导后股骨远端的骨小梁结构的变化，使用了一种可以被认为是对复杂表面不规则程度的定量描述的“分维”。数据来自连续49天内10次注射角叉菜胶致兔膝关节EIA的标本。将嵌入的股骨远端未脱钙横断面的摄影放大图像数字化，并使用在Sun工作站上编写的软件来定义图像中的可重复感兴趣区域(ROI)。用幂定律方法对感兴趣区进行了分形分析。通过对数据拟合公式(Epsilon)=lambda epsilon((2-D))，估计了ROI内骨小梁模式的分维。在这个等式中，A(Epsilon)是通过将ROI数据建模为三维结构而形成的“表面”的面积，其中灰度级大小提供第三维，lambda是比例常数，epsilon是用于测量面积的测量“工具”的大小，D是分维。对所有ROI数据的平均值进行Mann-Whitney U检验表明，两种分维分布有显著差异(p<；0.005)，关节炎数据点(这些值较高)与正常组(每组n=11)之间只有两个重叠。由于Howship的骨陷窝太小，不能在所使用的系统中解决，我们认为分维的差异主要与小梁表面取向有关，而不是由于炎性关节炎影响的骨转换增加而导致的粗糙(吸收灶)的增加。结果表明，在类似于环境影响评价的条件下，分维可以作为评估骨小梁结构损伤程度的有用工具。
Our previous studies in experimental inflammatory arthritis (EIA) and in human rheumatoid arthritis demonstrated rapid remodeling with a 5-fold increase in bone resorption and bone formation. Normal condylar trabecular bone is typically anisotropic, dth its orientation along lines of stress; rapid remodeling in a pathological state could disturb the usual order of trabeculae. This study assessed change in the structure of trabecular bone of the distal femoral epiphysis after induction of EIA, using a measure of "fractal dimension," which may be considered a quantitative description of the degree of irregularity of complex surfaces. Data was obtained from specimens in which EIA had been induced in the rabbit knee by 10 injections of carrageenan over 49 days. Photographic enlargements of embedded undecalcified cross-sections of the distal femur were digitized, and software written on a Sun workstation was used to define repeatable regions of interest (ROIs) in the images. The ROIs were subjected to fractal analysis by a power law method. The fractal dimension of the trabecular bone pattern within the ROI was estimated by fitting an equation of the formA(epsilon) = lambda epsilon((2-D)) to the data. In this equation, A(epsilon) is the area of the "surface" formed by modeling the ROI data as a three-dimensional structure with the grey-level magnitude providing the third dimension, lambda is a scaling constant, epsilon is the size of the measuring "tool" used to measure the area, and D is the fractal dimension. A Mann-Whitney U-test applied to the average of the data from all ROIs showed that the two distributions of fractal dimension were significantly different (p < 0.005), There were only two overlaps between data points for arthritis (with these values higher) and normal groups (n = 11 for each group). Since Howship's lacunae were too small to be resolved in the system utilized, we consider the difference in fractal dimension to be primarily related to trabecular surface orientation, rather than to the increased number of asperities (resorptive foci) occurring due to increased turnover in bone affected by inflammatory arthritis. The results suggest that fractal dimension may be a useful tool for assessing the degree of structural damage to trabeculae in conditions similar to EIA.