When bone implants are loaded, they are inevitably subjected to displacement relative to bone. Such micromotion generates stress/strain states at the interface that can cause beneficial or detrimental sequels. The objective of this study is to better understand the mechanobiology of bone healing at the tissue-implant interface during repeated loading. Machined screw shaped Ti implants were placed in rat tibiae in a hole slightly bigger than the implant diameter. Implants were held stable by a specially-designed bone plate that permits controlled loading. Three loading regimens were applied, (a) zero loading, (b) one daily loading session of 60 cycles with an axial force of 1.5 N/cycle for 7 days, and (c) two such daily sessions with the same axial force also for 7 days. Finite element analysis was used to characterize the mechanobiological conditions produced by the loading sessions. After 7 days, the implants with surrounding interfacial tissue were harvested and processed for histological, histomorphometric and DNA microarray analyses. Histomorphometric analyses revealed that the group subjected to repeated loading sessions exhibited a significant decrease in bone-implant contact and increase in bone-implant distance, as compared to unloaded implants and those subjected to only one loading session. Gene expression profiles differed during osseointegration between all groups mainly with respect to inflammatory and unidentified gene categories. The results indicate that increasing the daily cyclic loading of implants induces deleterious changes in the bone healing response, most likely due to the accumulation of tissue damage and associated inflammatory reaction at the bone-implant interface.

当骨植入物被加载时，它们不可避免地会相对于骨骼发生位移。这种微动会在界面处产生应力/应变状态，从而导致有益或有害的后果。本研究的目的是更好地了解重复加载过程中组织 - 植入物界面处骨骼愈合的力学生物学。将机械加工的螺钉形钛植入物置于大鼠胫骨中一个略大于植入物直径的孔中。植入物通过特殊设计的骨板保持稳定，允许控制负载。应用了三种负荷方案，(a) 零负荷，(b) 60 个循环的每日负荷会话，轴向力为 1.5 N/周期，持续 7 天，(c) 两个这样的日常会话，同样的轴向力也用于7天。有限元分析用于表征由加载会话产生的机械生物学条件。7 天后，收集并处理具有周围界面组织的植入物，用于组织学、组织形态计量学和 DNA 微阵列分析。组织形态计量学分析显示，与未加载的植入物和仅接受一次加载的组相比，接受重复加载的组表现出骨与植入物接触的显着减少和骨与植入物的距离增加。在所有组之间的骨整合过程中，基因表达谱不同，主要是在炎症和未鉴定的基因类别方面。结果表明，增加种植体的每日循环负荷会导致骨愈合反应发生有害变化，