Department of Infrastructure Engineering, The University of Melbourne, Parkville, Australia.
Epworth Hospital Richmond, Victoria, 3121, Australia.
J Mech Behav Biomed Mater. 2021 Sep;121:104611. doi: 10.1016/j.jmbbm.2021.104611. Epub 2021 May 28.
It is known that weight-bearing exercises under Ilizarov circular fixators (ICF) could enhance bone fracture healing by mechano-regulation. However, interfragmentary movements at the fracture site induced by weight-bearing may inhibit angiogenesis and ultimately delay the healing process. To tackle this challenge, a computational model is presented in this study which considers the spatial and temporal changes in mechanical properties of fracture callus to predict optimal levels of weight-bearing during fracture healing under ICF. The study takes sheep fractures as example and shows that the developed model has the capability of predicting patient specific, time-dependent optimal levels of weight-bearing which enhances mechano-regulation mediated healing without hindering the angiogenesis process. The results demonstrate that allowable level of weight-bearing and timings depend on fracture gap size. For normal body weights (BW) and moderate fracture gap sizes (e.g. 3 mm), weight-bearing with 30% BW could start by week 4 post-operation and gradually increase to 100% BW by week 11. In contrast, for relatively large fracture gap sizes (i.e. 6 mm), weight-bearing is recommended to commence in later stages of healing (e.g. week 11 post-operation). Furthermore, increasing ICF stiffness (e.g. using half pins instead of pretension wires) can increase the level of weight-bearing significantly in the early stages up to a certain time point (e.g. week 8 post-operation) beyond which no noticeable benefits could be achieved. The findings of this study have potential applications in designing post-operative weight bearing exercises.
已知伊里扎洛夫环形外固定架（ICF）下的负重运动可以通过机械调节增强骨折愈合。然而，负重引起的骨折部位的断端间运动可能会抑制血管生成，最终延迟愈合过程。为了解决这一挑战，本研究提出了一个计算模型，该模型考虑了骨折痂机械性能的时空变化，以预测在 ICF 下骨折愈合过程中负重的最佳水平。该研究以绵羊骨折为例，表明所开发的模型具有预测患者特定、随时间变化的最佳负重水平的能力，这种能力增强了机械调节介导的愈合，而不会阻碍血管生成过程。结果表明，允许的负重水平和时间取决于骨折间隙的大小。对于正常体重（BW）和中等骨折间隙大小（例如 3mm），术后第 4 周即可开始负重 30% BW，并逐渐增加到第 11 周的 100% BW。相比之下，对于相对较大的骨折间隙大小（即 6mm），建议在愈合的后期开始负重（例如术后第 11 周）。此外，增加 ICF 的刚度（例如使用半针而不是预紧丝）可以在早期显著增加负重水平，直到某个时间点（例如术后第 8 周），此后不会有明显的益处。本研究的结果在设计术后负重运动方面具有潜在的应用价值。
