应变理论在骨折愈合中的临床应用

,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,应变理论在骨折愈合中的临床应用,骨折愈合的分型,应变的概念,基于Perren应变理论的一些AO理念,附：微动促进骨折愈合的一项研究要点,Fracture healing can be divided into two types:,primary or direct healing by internal remodeling;,secondary or indirect healing by callus formation,骨折愈合分为2种类型,通过内塑形的,一期或直接愈合,通过骨痂形成的,二期或间接愈合,直接愈合,occurs only with absolute stability and is a biological process of osteonal bone remodeling,仅发生在,绝对稳定,固定时，它是骨单位重建的生物过程,绝对稳定使骨折部位的修复组织在生理负荷下的应变完全消除,将应变减少到临界值以下可以减少骨痂形成的刺激，使骨折的愈合没有出现肉眼可见的骨痂,间接愈合,occurs with relative stability (flexible fixation methods). It is very similar to the process of embryological bone development and includes both intramembraneous and endochondral bone formation. In diaphyseal fractures, it is characterized by the formation of callus.,发生于相对稳定固定时（弹性固定方法），包括膜内成骨和软骨成骨,除了加压技术外，所有的固定方法均可视为弹性固定，提供相对稳定性。,其特点是,骨痂形成,Bone healing can be divided into four stages:,inflammation;,soft callus formation;,hard callus formation;,remodeling.,骨折间接愈合的四个阶段,炎性期,软骨痂形成期,硬骨痂形成期,重塑形期,Interfragmentary movement stimulates the formation of a callus and accelerates healing,骨痂形成需要一定程度的力学刺激,骨折块之间的相对活动可刺激骨痂的形成，加速骨折的愈合,Perrens strain theory,The manner in which mechanical factors influence fracture healing is explained by Perrens strain theory.,Perren SM, Cordey J (1980) The concept of interfragmentary strain. Berlin Heidelberg New York: Springer-Verlag.,Perren应变理论解释了机械力学因素对于骨折愈合的影响,Perrens strain theory,Perren应变理论,Motion at the fracture results in deformation producing strain in the granulation tissue at the fracture site.,骨折端的活动引起的形变会在骨折端肉芽组织中产生应变,Strain-应变,Strain is the deformation of a material when a given force is applied.,Normal strain is the change in length ( l) in comparison to original length (l)when a given load is applied. Thus, it has no dimensions and is often expressed as a percentage.,在应力作用下，材料在单位长度内发生的形变,对材料施加应力后其长度发生的变化,没有单位，通常用百分比表示,=（L-L。）/L。,= L/L,组织在功能正常状态下可耐受的变形程度有很大的变化范围,完整骨骼的正常应变程度为2%（骨折发生前）,肉芽组织的应变能力为100%,在早期，当骨痂主要成分为软组织时，骨折端耐受畸形或组织应变的强度要大于后期的骨性骨痂,The amount of deformation that a tissue can tolerate and still function varies greatly. Intact bone has a normal strain tolerance of 2% (before it fractures), whereas granulation tissue has a strain tolerance of 100%.,Bony bridging between the distal and proximal callus can only occur when local strain (ie, deformation) is less than the forming woven bone can tolerate.,Thus, hard callus will not bridge a fracture gap when the movement between the fracture ends is too great,Thus, overloading of the fracture with too much interfragmentary movement later in the healing process is not well tolerated,只有当局部的应变小于编织骨所能耐受的程度，远近端的骨痂才能发生骨性连接,因此，当骨折端的活动过大时，硬骨痂无法桥接骨折端,在骨折愈合的后期，过度的负荷使骨折块发生过多的活动不利于骨折的愈合,Callus formation will not take place when the strain is too low,A low-strain environment will be produced if the fixation device is too stiff, or if the fracture gap is too wide . Delayed healing and nonunion will result,但是，当应变过小时骨痂无法形成,当固定装置过于坚硬或骨折间隙过宽时，会产生低应变的环境，此时可发生骨折不愈合或延迟愈合,根据Perrens strain theory,the strain is the higher the smaller the gap is.,The same deforming force produces more strain at the site of a simple fracture than at that of a multifragmentary fracture.,骨折间隙越小，应变越大,相同的应力作用于简单骨折和粉碎骨折，其中简单骨折产生的应变较大,Multifragmentary fractures tolerate more motion between the two main fragments because the overall movement is shared by several fracture planes, which reduces the tissue strain or deformation at the fracture gap.,粉碎骨折可耐受两个主要骨折块之间有更大范围的活动,因为其总的活动被不同的骨折平面所分担，因此减少了骨折间隙中组织的应变,A perfectly reduced simple fracture (small gap) stabilized under compression (absolute stability and low strain) heals without external callus (direct healing).,简单骨折（间隙小）解剖复位加压固定（绝对稳定，低应变）后，骨折发生无外骨痂的愈合（直接愈合）,A simple fracture (small gap) fixed with a bridging plate (relative stability) is exposed to movement (high strain). Fracture healing is delayed or will not occur at all,简单骨折（间隙小）用桥接钢板（相对稳定）固定后，骨折端的活动导致高应变，骨折愈合延迟甚至不愈合,Today there is clinical experience and experimental proof that flexible fixation can stimulate callus formation, thereby accelerating fracture healing .,This can be observed in diaphyseal fractures splinted by intramedullary nails, external fixators, or bridging plates,已有临床和实验室证据表明弹性固定可刺激骨痂的形成，从而促进骨折的愈合,骨干骨折后，使用随内钉、外固定架、桥接钢板固定可观察到这一现象,In a complex fracture (large gap) fixed with a bridging plate (relative stability) the strain will be low in spite of movement, and fracture healing will occur with callus formation (indirect bone healing).,复杂骨折（间隙大）用桥接钢板（相对稳定）固定后，骨折端虽有活动，但应变低，骨折发生有骨痂形成的愈合（间接愈合）,外部机械刺激对应用弹性外固定固定的骨干截骨模型愈合作用的研究,Background,It is generally accepted that small interfragmentary movements (IFMs) yield better bone healing results than larger IFMs ( 1 mm).,However, the optimal size of IFM within the l-mm range remains undetermined.,Objective,The purpose of this study was to investigate the effect of an externally applied mechanical stimulus on fracture healing under flexible fixation.,Design,Stimulation of fracture healing under various conditions of interfragmentary movement in an in vivo fracture model on 41 sheep,Methods,Standardized transverse osteotomy of 3 mm gap size in the left ovine tibia was fixed with an unilateral external fixator.,To perform controlled axial micromovement, a custom-designed stimulation module was applied to the fixator rods (Fig. 1). The module was electromechanically driven and controlled by a microprocessor .,Methods,The sheep were divided into four IFM groups of 0.0, 0.2, 0.4 and 0.8 mm,and stimulated with this litude（振幅） for 1200 cycles per day at 1 Hz.,External dynamization began 12 days post-op.,Methods,After a healing period of 6 weeks,bone mineral density,and biomechanical stability,were evaluated to determine the quality of healing.,Results,The amount of callus formation increased significantly with increasing IFM (PO.O5).,Results,However, highest biomechanical stability of the healed bone and mineral density of the gap tissue was achieved with an IFMs of 0.4 mm. although the differences were not significant.,Conclusions,These results suggest that the optimal interfragmentary movement for acceleration of delayed fracture healing is in the range of 0.5 mm,