Department of Mechanical Engineering, École Polytechnique de Montréal, P.O. Box 6079, Station Centre-Ville, Montréal, QC, H3C 3A7, Canada.
Biomech Model Mechanobiol. 2012 Mar;11(3-4):303-12. doi: 10.1007/s10237-011-0310-6. Epub 2011 May 11.
The objectives of this study were to extract the intrinsic mechanical properties of the growth plate at four different stages of growth and to compare two different methods of extracting these properties. Porcine distal ulnar growth plate samples were obtained from newborn, 4-, 8-, and 18-week (W) pigs and were tested using stress relaxation tests under unconfined compression. A four-parameter curve fitting procedure was developed to extract mechanical properties using the Transversely Isotropic Biphasic Elastic model(TIBPE) (Cohen et al. in J Biomech Eng Trans Asme 120(4):491-496, 1998) and the Differential Evolution (DE) optimization algorithm (Price et al. Natural computing series, Springer, Germany 2005). Optimization was done on all experimental curves for the first method and on one average experimental curve per developmental stage in the second. The 4-week stage was studied in two subgroups (a) and (b) due to distinct differences in mechanical properties. Intrinsic mechanical properties of the growth plate varied nonlinearly with developmental stage. Both methods showed that transverse and out-of-plane Young's moduli (E (1), E (3)) decrease with developmental stage, whereas transverse permeability (k (1)) increases. The exception is a sharp increase in stiffness and reduction in permeability at the 4W(a) stage, which may be associated with rapid porcine developmental changes at the 3-4 week period. The second method provides a more reliable representation of the average mechanical behavior, whereas the first method allows statistical comparison of optimized mechanical properties. This study characterizes, for the first time, the variation in growth plate mechanical properties for the same animal (porcine) and bone (ulna) model with developmental stage and provides new insight into the progression of musculoskeletal diseases during growth spurts in response to mechanical loading.
本研究的目的是提取生长板在四个不同生长阶段的固有机械性能，并比较两种提取这些性能的不同方法。从新生、4 周、8 周和 18 周（W）猪的猪远端尺骨生长板样本中获得，并在无约束压缩下进行应力松弛试验。开发了一个四参数曲线拟合程序，使用横向各向同性双相弹性模型（TIBPE）（Cohen 等人，J Biomech Eng Trans Asme 120（4）：491-496，1998）和差分进化（DE）优化算法（Price 等人，自然计算系列，Springer，德国 2005 年）提取机械性能。第一种方法对所有实验曲线进行了优化，第二种方法对每个发育阶段的一条平均实验曲线进行了优化。由于机械性能存在明显差异，4 周阶段分为两个亚组（a）和（b）进行研究。生长板的固有机械性能随发育阶段呈非线性变化。两种方法均表明，横向和平面外杨氏模量（E（1），E（3））随发育阶段而降低，而横向渗透率（k（1））增加。例外的是在 4W（a）阶段刚度急剧增加和渗透率降低，这可能与 3-4 周期间猪的快速发育变化有关。第二种方法更可靠地代表了平均力学行为，而第一种方法允许对优化后的力学性能进行统计比较。本研究首次对同一动物（猪）和骨骼（尺骨）模型的生长板力学性能随发育阶段的变化进行了描述，并深入了解了在生长突增期间骨骼肌肉疾病对机械载荷的反应进展。
