应变理论在骨折愈合中的临床应用

1、应变理论在骨折愈合中的临床应用一点粗浅的了解2011-03-30n骨折愈合的分型n应变的概念n基于Perren应变理论的一些AO理念n附：微动促进骨折愈合的一项研究要点nFracture healing can be divided into two types:nprimary or direct healing by internal remodeling; nsecondary or indirect healing by callus formation n骨折愈合分为2种类型n通过内塑形的一期或直一期或直接愈合接愈合n通过骨痂形成的二期或二期或间接愈合间接愈合直接愈合noccurs

2、only with absolute stability and is a biological process of osteonal bone remodeling n仅发生在绝对稳定绝对稳定固定时，它是骨单位重建的生物过程n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n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noccurs with relative stability (flexible fixation methods). It is very similar to the process of embryological b

3、one development and includes both intramembraneous and endochondral bone formation. In diaphyseal fractures, it is characterized by the formation of callus. n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n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。n其特点是骨痂形成骨痂形成nBone healing can be divided into four stages:ninflammation; nsoft

4、 callus formation; nhard callus formation; nremodeling. n骨折间接愈合的四个阶段n炎性期n软骨痂形成期n硬骨痂形成期n重塑形期nInterfragmentary movement stimulates the formation of a callus and accelerates healing n骨痂形成需要一定程度的力学刺激n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 theorynThe manner in which mechanical factors influence fractur

5、e healing is explained by Perrens strain theory.nPerren SM, Cordey J (1980) The concept of interfragmentary strain. Berlin Heidelberg New York: Springer-Verlag.nPerren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nMotion at the fracture results in deformation producing strain in the granulat

6、ion tissue at the fracture site.n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nStrain is the deformation of a material when a given force is applied. nNormal 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 a

7、s a percentage. n在应力作用下，材料在单位长度内发生的形变n对材料施加应力后其长度发生的变化n没有单位，通常用百分比表示n=（L-L。）/L。n= L/Ln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n完整骨骼的正常应变程度为2%（骨折发生前）n肉芽组织的应变能力为100%n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nThe amount of deformation that a tissue can tolerate and still function varies greatly. Intact bone has a n

8、ormal strain tolerance of 2% (before it fractures), whereas granulation tissue has a strain tolerance of 100%. nBony bridging between the distal and proximal callus can only occur when local strain (ie, deformation) is less than the forming woven bone can tolerate. nThus, hard callus will not bridge

9、 a fracture gap when the movement between the fracture ends is too great nThus, overloading of the fracture with too much interfragmentary movement later in the healing process is not well toleratedn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n因此，当骨折端的活动过大时，硬骨痂无法桥接骨折端n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nCallus

10、 formation will not take place when the strain is too low nA 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 resultn但是，当应变过小时骨痂无法形成n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 theorynt

11、he strain is the higher the smaller the gap is.nThe same deforming force produces more strain at the site of a simple fracture than at that of a multifragmentary fracture.n骨折间隙越小，应变越大n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nMultifragmentary fractures tolerate more motion between the two main fragments becau

12、se the overall movement is shared by several fracture planes, which reduces the tissue strain or deformation at the fracture gap. n粉碎骨折可耐受两个主要骨折块之间有更大范围的活动n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nA perfectly reduced simple fracture (small gap) stabilized under compression (absolute stability and low stra

13、in) heals without external callus (direct healing). n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）nA 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 n简单骨折（间隙小）用桥接钢板（相对稳定）固定后，骨折端的活

14、动导致高应变，骨折愈合延迟甚至不愈合nToday there is clinical experience and experimental proof that flexible fixation can stimulate callus formation, thereby accelerating fracture healing . nThis can be observed in diaphyseal fractures splinted by intramedullary nails, external fixators, or bridging plates n已有临床和实验室证

15、据表明弹性固定可刺激骨痂的形成，从而促进骨折的愈合n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nIn 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). n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

16、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BackgroundnIt is generally accepted that small interfragmentary movements (IFMs) yield better bone healing results than larger IFMs ( 1 mm). nHowever, the optimal size of IFM within the l-mm range remains undetermined.ObjectivenThe purpose of this s

17、tudy was to investigate the effect of an externally applied mechanical stimulus on fracture healing under flexible fixation.DesignnStimulation of fracture healing under various conditions of interfragmentary movement in an in vivo fracture model on 41 sheepMethodsnStandardized transverse osteotomy o

18、f 3 mm gap size in the left ovine tibia was fixed with an unilateral external fixator. nTo 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 .MethodsnThe sheep were divided into four IFM groups of 0.0, 0.2, 0.4 and 0.8 mmn and stimulated with this amplitude（振幅） for 1200 cycles per day at 1 Hz. nEx