Warden S J, Turner C H
Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Bone. 2004 Feb;34(2):261-70. doi: 10.1016/j.bone.2003.11.011.
A dose-response relationship has been shown between loading frequency and cortical bone adaptation for frequencies of up to 10 Hz, and is presumed to persist with further increases in frequency. Studies herein aimed to investigate cortical bone adaptation to loading frequencies of 1, 5, 10, 20 and 30 Hz. Two studies were performed in adult C57BL/6 mice using the ulna axial compression-loading model. In the first study, the histomorphometric response of the ulna was studied when loaded for 120 cycles day(-1) for 3 days at one of the five frequencies and one of two load magnitudes (1.5 or 2.0 N). In the second study, the changes in ulna geometry and mechanical properties were studied following loading for 5 min day(-1), 3 days week(-1) for 4 weeks at one of the five frequencies and one of two load magnitudes (1.0 or 1.6 N). Preliminary strain gauge measurements showed that frequency had no effect on mechanical strain per unit load. In study 1, loading frequency significantly influenced bone adaptation when loading at 2.0 N, with loading at 10 Hz resulting in significantly greater adaptation than with loading at other frequencies. In study 2, loading frequency significantly influenced the change in geometry when loading at 1.6 N, with loading at 5, 10 or 30 Hz resulting in significantly greater change than with loading at 1 Hz. Loading at 5 Hz also resulted in significantly greater change than with loading at 20 Hz. No frequency effect was found on any of the mechanical properties at either load. Overall, we found cortical bone adaptation to mechanical loading to increase with increasing loading frequency up to 5-10 Hz and to plateau with frequencies beyond 10 Hz. The mechanism for this nonlinear frequency response is not known; however, based on strain gauge measurements, we do not believe it resulted from dampening associated with high frequency loading through the flexed carpal joint. The obtained findings may relate to the mechanism of mechanotransduction within the bone. This requires further investigation.
对于高达10Hz的频率，已表明加载频率与皮质骨适应性之间存在剂量反应关系，并且推测随着频率进一步增加这种关系依然存在。本文的研究旨在调查皮质骨对1、5、10、20和30Hz加载频率的适应性。使用尺骨轴向压缩加载模型在成年C57BL/6小鼠中进行了两项研究。在第一项研究中，在五个频率之一和两个载荷大小（1.5或2.0N）之一的条件下，以每天120次循环加载3天，研究尺骨的组织形态计量学反应。在第二项研究中，在五个频率之一和两个载荷大小（1.0或1.6N）之一的条件下，以每天加载5分钟、每周3天持续4周，研究加载后尺骨几何形状和力学性能的变化。初步应变计测量表明，频率对单位载荷下的机械应变没有影响。在研究1中，当载荷为2.0N时，加载频率显著影响骨适应性，10Hz加载时的适应性显著大于其他频率加载时的适应性。在研究2中，当载荷为1.6N时，加载频率显著影响几何形状变化，5、10或30Hz加载时的变化显著大于1Hz加载时的变化。5Hz加载时的变化也显著大于20Hz加载时的变化。在任一载荷下，均未发现频率对任何力学性能有影响。总体而言，我们发现皮质骨对机械加载的适应性随着加载频率增加至5-10Hz而增强，超过10Hz时则趋于平稳。这种非线性频率反应的机制尚不清楚；然而，基于应变计测量，我们认为它不是由通过弯曲腕关节的高频加载相关的阻尼引起的。所获得的发现可能与骨内的力传导机制有关。这需要进一步研究。
