Bonnevie Edward D, Delco Michelle L, Fortier Lisa A, Alexander Peter G, Tuan Rocky S, Bonassar Lawrence J
Sibley School of Mechanical and Aerospace Engineering, College of Engineering, Cornell University, Ithaca, NY, USA.
Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA.
Cartilage. 2015 Oct;6(4):226-32. doi: 10.1177/1947603515595071.
The objective of this study was to fully characterize the mechanics of an in vivo impactor and correlate the mechanics with superficial cracking of articular surfaces.
A spring-loaded impactor was used to apply energy-controlled impacts to the articular surfaces of neonatal bovine cartilage. The simultaneous use of a load cell and displacement sensor provided measurements of stress, stress rate, strain, strain rate, and strain energy density. Application of India ink after impact was used to correlate the mechanical inputs during impact with the resulting severity of tissue damage. Additionally, a signal processing method to deconvolve inertial stresses from impact stresses was developed and validated.
Impact models fit the data well (root mean square error average ~0.09) and provided a fully characterized impact. Correlation analysis between mechanical inputs and degree of superficial cracking made visible through India ink application provided significant positive correlations for stress and stress rate with degree of surface cracking (R (2) = 0.7398 and R (2) = 0.5262, respectively). Ranges of impact parameters were 7 to 21 MPa, 6 to 40 GPa/s, 0.16 to 0.38, 87 to 236 s(-1), and 0.3 to 1.1 MJ/m(3) for stress, stress rate, strain, strain rate, and strain energy density, respectively. Thresholds for damage for all inputs were determined at 13 MPa, 15 GPa/s, 0.23, 160 s(-1), and 0.59 MJ/m(3) for this system.
This study provided the mechanical basis for use of a portable, sterilizable, and maneuverable impacting device. Use of this device enables controlled impact loads in vitro or in vivo to connect mechanistic studies with long-term monitoring of disease progression.
本研究的目的是全面表征体内冲击器的力学特性，并将力学特性与关节表面的浅表性裂纹相关联。
使用弹簧加载冲击器对新生牛软骨的关节表面施加能量可控的冲击。同时使用测力传感器和位移传感器来测量应力、应力率、应变、应变率和应变能密度。冲击后应用印度墨水来将冲击过程中的力学输入与由此产生的组织损伤严重程度相关联。此外，还开发并验证了一种从冲击应力中解卷积惯性应力的信号处理方法。
冲击模型与数据拟合良好（均方根误差平均值约为0.09），并提供了全面表征的冲击。通过应用印度墨水使可见的力学输入与浅表性裂纹程度之间的相关性分析表明，应力和应力率与表面裂纹程度呈显著正相关（分别为R(2)=0.7398和R(2)=0.5262）。对于应力、应力率、应变、应变率和应变能密度，冲击参数范围分别为7至21兆帕、6至40吉帕/秒、0.16至0.38、87至236秒(-1)和0.3至1.1兆焦/立方米。该系统所有输入的损伤阈值分别确定为13兆帕、15吉帕/秒、0.23、160秒(-1)和0.59兆焦/立方米。
本研究为使用便携式、可消毒且可操纵的冲击装置提供了力学基础。使用该装置能够在体外或体内实现可控的冲击载荷，从而将机理研究与疾病进展的长期监测联系起来。
