Mejia L C, Brierley T J
MTS Systems Corporation, Minneapolis, Minnesota.
Biomed Mater Eng. 1994;4(4):259-71.
A multistation (8-station) hip simulator has been designed and tested that provides a practical imitation of the motions and loads seen by the hip joint during a typical walking cycle. A biaxial rocking motion of +/- 23 degrees is synchronized with the respective resultant forces of the extension-flexion (heel-strike to toe-off) movements of the leg. This particular simulator provides a practical engineering in vitro implementation of the walking cycle. It also provides a realistic and practical compromise between general wear screening devices (such as pin-on-disk systems) and the intensive research accomplished through full scale simulation (full 6 degree-of-freedom systems) and modeling. Evaluation of system performance shows that control of rpm (revolutions-per-minute) for the desired axial rotation of 1 Hz was kept to 60 cpm +/- 1 cpm for axial loads (per actuator) as high as 4500 Newtons. Although loading error was 2% in the peak load areas of interest (3000 Newton), station-to-station load control variability was less than .6%. Baseline wear studies with this simulator using ultra-high-molecular-weight polyethylene and Cobalt-Chromium (UHMWPE/CoCr) hip systems indicate an average specimen-to-specimen wear variability of less than 7% range after 5 million test cycles. Testing was performed in a calf serum environment at an equilibrium temperature of 33 degrees C.
已设计并测试了一种多站（8站）髋关节模拟器，它能切实模拟典型步行周期中髋关节所经历的运动和负荷。+/-23度的双轴摇摆运动与腿部屈伸（足跟触地到足尖离地）运动各自的合力同步。这种特殊的模拟器为步行周期提供了一种切实可行的体外工程实现方式。它还在一般磨损筛选装置（如销盘系统）与通过全尺寸模拟（全6自由度系统）和建模完成的深入研究之间达成了现实可行的折中。系统性能评估表明，对于高达4500牛顿的轴向载荷（每个执行器），将所需1赫兹轴向旋转的每分钟转速（rpm）控制在60转/分钟+/-1转/分钟。尽管在感兴趣的峰值载荷区域（3000牛顿）加载误差为2%，但各站之间的载荷控制变化率小于0.6%。使用超高分子量聚乙烯和钴铬合金（UHMWPE/CoCr）髋关节系统在该模拟器上进行的基线磨损研究表明，在500万次测试循环后，平均样本间磨损变化率在7%以内。测试在33摄氏度的平衡温度下于小牛血清环境中进行。
