UPMC Univ Paris 6, CNRS, Laboratoire d'Imagerie Paramétrique, France.
Bone. 2011 May 1;48(5):1202-9. doi: 10.1016/j.bone.2011.02.021. Epub 2011 Mar 2.
Ultrasound axial transmission (UAT), a technique using propagation of ultrasound waves along the cortex of cortical bones, has been proposed as a diagnostic technique for the evaluation of fracture healing. Quantitative ultrasound parameters have been reported to be sensitive to callus changes during the regeneration process. The aim of this work was to identify the specific effect of cortical bone mineralization on UAT measurements by means of numerical simulations and experiments using a reverse fracture healing approach. A cortical bovine femur sample was used, in which a 3mm fracture gap was drilled. A 3mm thick cortical bone slice, extracted from another location in the bone sample, was submitted to a progressive demineralization process with EDTA during 12 days. UAT measurements and simulations using a 1MHz probe were performed with the demineralized slice placed into the fracture gap to mimic different stages of mineralization during the healing process. The calcium loss of the slice due to the EDTA treatment was recorded everyday, and its temporal evolution could be modeled by an exponential law. A 50MHz scanning acoustic microscopy was also used to assess the mineralization degree of the bone slice at the end of the intervention. These data were used in the numerical simulations to derive a model of the time evolution of bone slice mechanical properties. From both the experiments and the simulations, a significant and progressive increase in the time of flight (TOF; p<0.001) of the propagating waves measured by UAT was observed during the beginning of the demineralization process (first 4 days). Although the simulated TOF values were slightly larger than the experimental ones, they both exhibited a similar time-dependence, validating the simulation approach. Our results suggest that TOF measured in axial transmission is affected by local changes of speed of sound induced by changes in local mineralization. TOF may be an appropriate indicator to monitor callus maturation.
超声轴向透射（UAT）技术是一种利用超声波在皮质骨皮层传播的技术，已被提议作为评估骨折愈合的诊断技术。已有报道称，定量超声参数对再生过程中骨痂变化敏感。本工作旨在通过数值模拟和使用反向骨折愈合方法的实验，确定皮质骨矿化对 UAT 测量的具体影响。使用皮质牛股骨样本，在该样本中钻 3mm 的骨折间隙。从骨样本的另一个位置提取 3mm 厚的皮质骨片，并在 12 天内用 EDTA 进行渐进脱矿化处理。使用 1MHz 探头进行 UAT 测量和模拟，将脱矿化的骨片放置在骨折间隙中，以模拟愈合过程中不同阶段的矿化。记录由于 EDTA 处理而导致骨片的钙损失，其时间演化可以用指数定律来建模。还使用 50MHz 扫描声学显微镜评估干预结束时骨片的矿化程度。这些数据用于数值模拟，以推导出骨片机械性能随时间变化的模型。从实验和模拟中，在脱矿化过程的开始（前 4 天），可以观察到通过 UAT 测量的传播波的飞行时间（TOF）显著且逐渐增加（p<0.001）。尽管模拟的 TOF 值略大于实验值，但它们都表现出相似的时间依赖性，验证了模拟方法。我们的结果表明，轴向透射测量的 TOF 受到局部矿化变化引起的局部声速变化的影响。TOF 可能是监测骨痂成熟度的合适指标。
