Graeff Christian, Chevalier Yan, Charlebois Mathieu, Varga Peter, Pahr Dieter, Nickelsen Thomas N, Morlock Michael M, Glüer Claus C, Zysset Philippe K
Medical Physics, Department of Diagnostic Radiology, Michaelisstrasse 9, D-24105 Kiel, Germany.
J Bone Miner Res. 2009 Oct;24(10):1672-80. doi: 10.1359/jbmr.090416.
Monitoring of osteoporosis therapy based solely on DXA is insufficient to assess antifracture efficacy. Estimating bone strength as a variable closely linked to fracture risk is therefore of importance. Finite element (FE) analysis-based strength measures were used to monitor a teriparatide therapy and the associated effects on whole bone and local fracture risk. In 44 postmenopausal women with established osteoporosis participating in the EUROFORS study, FE models based on high-resolution CT (HRCT) of T(12) were evaluated after 0, 6, 12, and 24 mo of teriparatide treatment (20 microg/d). FE-based strength and stiffness calculations for three different load cases (compression, bending, and combined compression and bending) were compared with volumetric BMD (vBMD) and apparent bone volume fraction (app. BV/TV), as well as DXA-based areal BMD of the lumbar spine. Local damage of the bone tissue was also modeled. Highly significant improvements in all analyzed variables as early as 6 mo after starting teriparatide were found. After 24 mo, bone strength in compression was increased by 28.1 +/- 4.7% (SE), in bending by 28.3 +/- 4.9%, whereas app. BV/TV was increased by 54.7 +/- 8.8%, vBMD by 19.1 +/- 4.0%, and areal BMD of L(1)-L(4) by 10.2 +/- 1.2%. When comparing standardized increases, FE changes were significantly larger than those of densitometry and not significantly different from app. BV/TV. The size of regions at high risk for local failure was significantly reduced under teriparatide treatment. Treatment with teriparatide leads to bone strength increases for different loading conditions of close to 30%. FE is a suitable tool for monitoring bone anabolic treatment in groups or individual patients and offers additional information about local failure modes. FE variables showed a higher standardized response to changes than BMD measurements, but further studies are needed to show that the higher response represents a more accurate estimate of treatment-induced fracture risk reduction.
仅基于双能X线吸收法（DXA）监测骨质疏松症治疗不足以评估抗骨折疗效。因此，将骨强度作为与骨折风险密切相关的变量进行评估具有重要意义。基于有限元（FE）分析的强度测量方法被用于监测特立帕肽治疗及其对全骨和局部骨折风险的相关影响。在参与EUROFORS研究的44名已确诊骨质疏松症的绝经后女性中，在特立帕肽治疗（20微克/天）0、6、12和24个月后，对基于T12高分辨率CT（HRCT）的FE模型进行评估。将三种不同负荷情况（压缩、弯曲以及压缩和弯曲联合）下基于FE的强度和刚度计算结果与体积骨密度（vBMD）、表观骨体积分数（app. BV/TV）以及基于DXA的腰椎面积骨密度进行比较。还对骨组织的局部损伤进行了建模。早在开始使用特立帕肽6个月后，所有分析变量就有了高度显著的改善。24个月后，压缩时的骨强度增加了28.1±4.7%（标准误），弯曲时增加了28.3±4.9%，而app. BV/TV增加了54.7±8.8%，vBMD增加了19.1±4.0%，L1-L4的面积骨密度增加了10.2±1.2%。比较标准化增加量时，FE变化显著大于骨密度测量值的变化，且与app. BV/TV的变化无显著差异。在特立帕肽治疗下，局部失效高风险区域的大小显著减小。特立帕肽治疗可使不同负荷情况下的骨强度增加近30%。FE是监测群体或个体患者骨合成代谢治疗的合适工具，并能提供有关局部失效模式的额外信息。FE变量对变化的标准化反应高于骨密度测量值，但需要进一步研究来表明更高的反应代表对治疗引起的骨折风险降低的更准确估计。
