Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, 14424 Potsdam, Germany; Berlin-Brandenburg School for Regenerative Therapies (BSRT), Charité - Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany.
Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, 14424 Potsdam, Germany.
Acta Biomater. 2014 Sep;10(9):4009-19. doi: 10.1016/j.actbio.2014.06.003. Epub 2014 Jun 12.
A fracture in bone results in a dramatic change of mechanical loading conditions at the site of injury. Usually, bone injuries heal normally but with increasing fracture gaps, healing is retarded, eventually leading to non-unions. The clinical situation of these two processes with different outcomes is well described. However, the exact relation between the mechanical environment and characteristics of the tissues at all levels of structural hierarchy remains unclear. Here we studied the differences in material formation of non-critical (1mm) and critical (5mm gap) healing. We employed a rat osteotomy model to explore bone material structure depending upon the different mechanical conditions. In both cases, primary bone formation was followed by secondary bone deposition with mineral particle sizes changing from on average short and thick to long and thin particles. Bony bridging occurred at first in the endosteal callus and the nanostructure and microstructure developed towards cortical ordered material organization. In contrast, in critical healing, instead of bridging, a marrow cavity closure was formed endosteal, exhibiting tissue structure oriented along the curvature and a periosteal callus with less mature material structure. The two healing processes separated between 4 and 6 weeks post-osteotomy. The outcome of healing was determined by the varied geometrical conditions in critical and non-critical healing, inducing completely different mechanical situations.
骨裂会导致受伤部位的机械加载条件发生剧烈变化。通常情况下，骨折会正常愈合，但随着骨折间隙的增加，愈合会受到阻碍，最终导致愈合不良。这两种过程的临床情况已有详细描述，但在结构层次的各个层面上，机械环境与组织特性之间的确切关系仍不清楚。在这里，我们研究了非关键性（1mm）和关键性（5mm 间隙）愈合在材料形成方面的差异。我们采用大鼠骨切开模型来研究不同机械条件下的骨材料结构。在两种情况下，初级骨形成后都会进行次级骨沉积，矿物质颗粒大小从短而粗变为长而细。首先在内骨痂中发生骨桥形成，纳米结构和微观结构朝着皮质有序材料组织发展。相比之下，在关键性愈合中，不是形成骨桥，而是在骨内膜形成骨髓腔闭合，表现出沿曲率排列的组织结构和具有较不成熟材料结构的骨外膜骨痂。两种愈合过程在骨切开术后 4 至 6 周之间分离。愈合的结果取决于关键性和非关键性愈合中不同的几何条件，这会导致完全不同的力学情况。
