运动锻炼后兔胫骨扭转载荷下的蠕变特性

背景：运动中骨组织的蠕变以微应变方式进行，且全骨的扭转能较为全面地反映骨组织的生物力学特性。目的：观察运动训练状态后兔胫骨扭转载荷下的蠕变特点。设计、时间及地点：平行对照动物观察性实验，于2005-05/2007-07在四川省骨科医院生物力学实验室完成。材料：6月龄日本大白兔32只，雌雄各半，分为实验组(n=24)和对照组(n=8)。方法：将实验组放入电刺激笼，训练量为每20 s刺激1次，刺激时间为0.1~0.2 s，动物受刺激后沿刺激笼跑跳数步并转弯，45 min/d，分3次进行，15 min/次，间隔15 min，每周训练5 d，连续训练4周。对照组饲养条件同实验组，不做训练。主要观察指标：取兔胫骨样本，在其前、后、左、右4面各粘贴应变计，在0.52 N•m转矩载荷下测试500 s内胫骨的微应变随时间的变化，即胫骨的蠕变。结果：在扭转载荷下，兔胫骨表现出明显的蠕变现象，在约2 s时间内迅速达到蠕变曲线的拐点，然后以较为缓慢的速率发生蠕变。训练4周后，实验组胫骨前后侧蠕变明显小于对照组；对照组前侧蠕变最大，明显大于内侧，训练后实验组前侧蠕变最小，明显小于外侧蠕变(P < 0.05)。结论：胫骨各向蠕变特性不同，胫骨前后侧变形较内外侧大，经过一段时间运动训练后，兔胫骨蠕变特性发生了变化，其前后侧蠕变明显减小。

Creep characterizes of rabbit tibia under torsion load following exercise

BACKGROUND: The creep performance of bone tissues during exercise is achieved through the microstrain, and the holosteous torsion can completely reflect the biomechanical characteristics of bone tissues. OBJECTIVE: To determine the creep characteristics of rabbit tibia under the torsion load following exercise. DESIGN, TIME AND SETTING: A parallel controlled animal observational experiment was performed at the Laboratory of Biomechanics in Orthopedic Hospital of Sichuan Province between May 2005 and July 2007. MATERIALS: A total of 32 Japanese white rabbits, irrespective of genders, aged 6 months, were divided into exercise group (n=24) and control group (n=8). METHODS: Exercise group animals were placed in cage to receive electrical stimulus, 0.1-0.2 seconds once every 20 seconds. Following the stimulation, the animals ran and jumped for several paces along with the cage and made a turn, 15 minutes once, three times per day, totally 45 minutes, at the interval of 15 minutes. The exercise was carried out five days per week for 4 successive weeks. The control group was fed as exercise group, but received no exercise.MAIN OUTCOME MEASURES: After 4 week exercise, the tibias were griped by the torsion clamping apparatus, the creep characterizes of anterior, posterior, medial and lateral sides of tibia under 0.52 N•m torsion load within 500 seconds were determined by strain gauge technique.RESULTS: Under torsion load, the creeps were present obviously in the rabbit tibia, reached the creep curve inflection point at 2 seconds, and then gradually appeared. After 4 weeks, the creeps of tibias at anterior and posterior side in the exercise group were less than control group; in the control group, the anterior side of tibia was remarkably greater than the medial side. After exercise, the creep was the smallest in anterior side, which was less than the lateral side (P < 0.05).CONCLUSION: The creep characteristics of tibia are anisotropic, the deformation at the anterior and posterior sides is greater than that at the medial and lateral sides. Exercise can alter the creep characteristics of rabbit tibia and reduces the creep at the anterior and posterior sides.