锁定钢板现状：优点、缺点、失败之处.doc

The Current Status of Locked Plating: The Good,the Bad, and the Ugly锁定钢板现状：优点、缺点、失败之处Abstract: Locked plate technology has evolved in an effort to overcome the limitations associated with conventional plating methods, primarily for improving xation in osteopenic bone. The development of screw torque and plate-bone interface friction is unnecessary with locked plate designs, signicantly decreasing the amount of soft tissue dissection required for implantation, preserving the periosteal blood supply, and facilitating the useof minimally invasive percutaneous bridging xation techniques. The locked plate is a xed-angle device because angular motion does not occur at the plate screw interface. The use of locked plate technology allows the orthopaedic surgeon to manage fractures with indirect reduction techniques while providing stable fracture xation. The securefeel of locked plates, ease of application, and the low incidence of complications noted in early clinical reports have contributed to the proliferation of this technology. Along with reports of clinical successes, as the use of xed angle/locked plates has increased, clinical failures are being noticed. This review will focus on the biomechanics of locked plate technology, appropriate indications for its use, laboratory and clinical comparisons to conventional plating techniques, and potential mechanisms of locked plate failure that have been observed.摘要：锁定钢板技术致力于克服传统钢板固定方法的局限性，并主要用于提高骨质减少的骨头的固定效果。锁定钢板的设计无需顾及螺钉扭矩和钢板与骨接触面的摩擦力，显著减少为了内固定植入所需的软组织剥离，保护了骨膜的血运，而且更有利于微创经皮桥接固定技术的使用。由于螺钉与钢板的接触面无法发生角度运动，锁定钢板是一种固定角度装置。锁定钢板技术的运用使得骨科医生可以对骨折进行间接复位并达到稳定的固定。由于早期临床报道认为锁定钢板安全、容易使用、并发症低，此项技术得以迅速推广。当固定角度（锁定）钢板使用的不断增加，伴随着临床成功报道的是临床失败逐渐被重视。本篇综述将着重于锁定钢板技术的生物力学、使用的恰当指征、与传统钢板固定技术的实验室和临床比较、以及已被发现的失败潜在机制。/colorKey Words: locked plate, failure, complications(J Orthop Trauma 2008;22:479关键词：锁定钢板，失败，并发症(创伤骨科杂志 2008;22:479486)/colorINTRODUCTION前言：For the past 50 years, the general principles of fracture xation have been developed, tested, and promoted by the AO group. 1,2The original principles included direct fracture exposure, precise reduction, and rigid internal xation through compression in an effort to achieve an anatomic fracture union.3,4This conventional fracture management technique often required a signicant surgical exposure, altering the biologic environment at and around the fracture site through soft tissue stripping and devascularization.4,5Consequences of iatrogenic soft tissue trauma, however, often resulted in the development of delayed fracture union, nonunion, and infection.在过去的50年里，AO组织提出、检验、推广了骨折固定的一般原则。最初的原则包括骨折端直接暴露、精确复位、通过加压达到坚强的内固定以期取得解剖性骨折愈合。这种传统的骨折治疗技术通常需要显著的外科暴露，并且因软组织剥离和血供的破坏造成了骨折端及其周围生物环境的改变。然而，这种医源性的软组织创伤经常造成骨折的延迟愈合、不愈合以及感染。A rened understanding of bone biology and the roles tissue vascularity and gap strain play in fracture healing, contributed to the development of the concept of bridging plateosteosynthesis and the use of locked plate technology.3,5The success of bridging xation spurred an interest in creation of an internal xator. The Schuhli-Nut, Pc-Fix, and Zespol plates were early attempts at creating an internal xator. 6,7By rmly xing the screw to the plate, the plate screw construct could act as a xed-angle device, with the screws functioning as threaded locked bolts. 4,8,9 Similar to the bars of an external xator, plates were not applied directly to the bone, thereby providing elastic xation, which facilitated fracture union through secondary bone healing with callus formation. 3,5,9Free of the need to apply the plates directly to the bony surface,the locked plate created a more biologic approach to the management of fractures, allowing for indirect reduction using minimally invasive percutaneous plating techniques.对骨骼生物学、组织血供的作用以及骨折愈合的间隙应变的加深理解，导致了桥接钢板接骨术观念的发展和锁定钢板技术的应用。桥接固定的成功助长了研制新内固定的兴趣。Schuhli锁定螺母、点接触钢板、Zespol钢板在早期都被尝试当作一个新的内固定。将螺钉牢靠地固定于钢板，并且通过锁定螺纹锁住，那么钢板螺钉构造就成了固定角度装置。与外固定架的管棒类似，锁定钢板没有直接置于骨头之上，而是提够一种弹性固定，使得骨折通过骨痂的形成达到二期愈合。不需要直接安置于骨表面，让锁定钢板成为骨折治疗的生物学固定的途径，允许使用微创经皮钢板技术进行间接复位。The secure feel of locked plates, the relative ease of application, and the low incidence of complications reported in early clinical studies contributed to the proliferation of this technology for fracture xation. Laboratory and clinical studies demonstrated that locked plate xation for certain fracture types provided superior construct stability and improved outcomes.4,1017As the use of xed-angle/locked plates increased, reports of clinical failures came along with reports of clinical successes. As a result, the current paper reviews the biomechanics of locked plate technology, appropriate indications for its use, laboratory and clinical comparisons with conventional xation techniques, and identies the potential mechanisms of locked plate failure that have been observed.由于早期临床报道认为锁定钢板安全、相对容易使用、并发症低，此项技术得以在骨折固定中迅速推广。实验室和临床研究表明，对于特定类型骨折，锁定钢板固定达到了更好的构造稳定性和更佳的效果。当固定角度（锁定）钢板使用的不断增加，临床成功与失败的报道相伴出现。因此，本篇综述将着重于锁定钢板技术的生物力学、使用的恰当指征、与传统钢板固定技术的实验室和临床比较、以及区分已被发现的失败潜在机制。Biomechanics of Locked Plate Technology锁定钢板技术的生物力学：Fracture xation with traditional compression plating techniques uses the frictional force created between the plate and bone to counteract the external forces experienced at the fracture site.18Stability with these traditional plate and screw constructs is primarily achieved via screw torque. Variables such as bone quality and fracture comminution affect the quality of screw thread purchase and the resultant xation stability achieved with compression plating. By a variety of mechanisms, the screws in a locked plating system are designed to lock into the plate, eliminating screw toggle and creating a xed-angle, single-beam construct. 3,8When using locked plates in a bridging manner, the edges of the fracture are not compressed together at the fracture site as is commonplace with conventional plating techniques.4Instead, the locked plate acts as an internal-external xator to bridge the fracture, providing relative stability while allowing enough strain at the fracture site to promote secondary healing with callus formation.3,5,8,9传统加压钢板技术进行骨折固定是利用钢板与骨之间的摩擦力来对抗骨折端的外来应力。这种传统钢板螺钉构造主要通过螺钉扭矩来获得稳定性。许多因素诸如骨骼质量和粉碎性骨折都会影响螺钉的抓持力和加压钢板的固定效果。而锁定钢板系统通过一系列机制将螺钉设计成与钢板相锁定，避免螺钉的滑动，从而形成一种固定角度的单横梁构造。传统钢板技术通常需要进行骨折端加压，采用锁定钢板进行桥接固定时则不需这样。相反，锁定钢板如同一种内置的外固定架对骨折进行桥接，在骨折端达到相对稳定固定的同时创造足够的应变来刺激骨痂形成以提高二期骨愈合。Biomechanically, the locked plate system is designed to convert the shear forces experienced at the implant with the application of load into compressive forces at the screw -bone interface.3,19 This force conversion is benecial in fracture xation because cortical bone is stronger against compressive loads than shear loads. Additionally, the angular stability of locked screws allows the applied load to be more evenly distributed amongst the component screws, avoiding signicant load concentration at a single screw-bone interface.3,4,20This leads to the overall xation strength of thelocked plate system, equaling the sum of xation strengths of all screw-bone interfaces instead of that of a single component screw as in conventional plating.3,8,19,20在生物力学上，锁定钢板系统设计成能将负荷下内固定的剪切力转换为螺钉与骨之间的压力。这种力学转换有利于骨折的固定，因为皮质骨对抗压缩负荷强于剪切负荷。而且，锁定螺钉的角度稳定性能将承受应力更有效地分散于各个组件，避免了单个骨螺钉界面的应力集中。这些方面使得锁定钢板系统的总体固定力度等于所有单个骨螺钉接触面固定力度的总和，而不是如同传统钢板固定那样由单个螺钉组件来承担。Acting as an internal-external xator, the xation rigidity of the locked plate system benets from the proximity of the plate to the bone and fracture site, with locked screw lengths being signicantly shorter than conventional external xator pins.3The overall stability provided by the locked plate system across the fracture site becomes dependent on the amount of load applied and the mechanical properties of the plate itself.3,4The extent of the elastic motion that occurs is dictated by the length of the plate, the cross-sectional area of the plate, the material properties of the plate, the density and diameter of the inserted screws, and the use of unicortical versus bicortical screws. 3,4,21 The choice of locked plate length is a key element in the fracture xation stability provided by the construct and varies according to fracture pattern.22Recommendations regarding the length of the locked plate typically include using an implant that is 8 to 10 times the length of the fracture in simple patterns and 3 times the length in comminuted fracture patterns. 4,21,23,24At least 2 screws per main fragment should be inserted, with 3 cortices of purchase for simple fractures and at least 2 screws and 4 cortices for comminuted fractures. 3,21,24,25 Additionally, a screw-to-hole ratio less than 0.5 limits the bending moments experienced at the most proximal and distal screws, and a span of 2 to 3 open screw holes should be left over the fracture site to help limit the concentration of stress at the adjacent screw-bone interfaces.4,23,26,27锁定钢板系统充当了一种内置的外固定架角色，但由于钢板与骨骼和骨折端的近距离接触提高了固定的强度，使得锁定螺钉的长度大大短于通常的外固定针。它所达到的总体稳定性取决于施加的负荷总量和钢板自身的力学特性。而其弹性活动范围取决于钢板长度、钢板横断面积、植入螺钉的密度和直径，使用单层皮质骨螺钉则优于双皮质骨螺钉。锁定钢板长度的选择对于骨折固定的稳定性至关重要，并且因骨折类型而异。通常来讲，对于简单类型骨折，锁定钢板的长度建议为骨折端长度的8-10倍，而在粉碎性骨折则为3倍。简单类型的骨折每个主要骨折块至少需要2枚螺钉固定3层皮质，而粉碎性骨折至少需要2枚螺钉固定4层皮质。并且，螺钉-钉孔比例小于0.5则限制了最近端和最远端螺钉的弯曲力矩；为了减少螺钉与骨交界面附近的应力集中，需要闲置2-3个钉孔的跨度越过骨折端。Newer locked plate designs, including those using combination-hole technology, allow surgeons to incorporate aspects of locked plating and compression plating into 1implant. In combining the two xation methods, the surgeon potentially negates the theoretical advantages of each, creating an environment at the fracture site, where excessive gap strains lead to the development of nonunion. 3,5An example of this(Figure 1) occurs when the ends of a simple fracture are brought within close proximity but are not compressed. In this situation, the stiffness of the plate and rigidity of the construct prevent bone contact, while the strains at the persistent fracture gap prohibit the formation of bone. This is complicated by the fact that the only way for the locked plate to dynamize is to undergo plastic deformation or break. Combination plates may be useful in certain fracture patterns in which one aspect of the fracture would benet from anatomic reduction and compression (ie, intraarticular component or simple fracture patterns in pathological bone), whereas another fracture component would benet from bridging xation (ie, comminuted metadiaphyseal portion).3,4However, when these criteria are met, it is important to complete maximal fracture compression with lag screws before locked screws are inserted, and the plate should be placed on the tension side of the fracture to neutralize the forces acting on the interfragmentary compression screws.3更新设计的锁定钢板，采用了复合孔技术，允许外科医生在一种内固定上同时使用锁定技术和加压技术。而联合使用两种技术时，外科医生容易忽略了彼此理论上的优点，造成骨折端存在着过大的间隙应变而导致骨折不愈合。其中一个例子（图1）就是因简单类型的骨折端只有靠近没有加压造成的。在这种情况下，钢板的硬度和整个构件的强度妨碍了骨折端的接触，持续的折端间隙应变阻止了骨愈合。如是还可并发形成钢板动力化引起塑性变形或者断裂。复合钢板对于特定类型骨折有着特定作用，解剖复合和加压有利于某些骨折固定（如关节内骨折或者简单类型的病理性骨折），而桥接固定有利于另外类型骨折（如粉碎性干骺端区域）。然而，这些标准要成立的前提是使用拉力螺钉达到骨折端的最大加压并且钢板需置于张力侧以中和折块间加压螺钉承受的应力。Indications for Locked Plate Fixation锁定钢板固定指征：The current indications for locked plate xation include complex periarticular fractures, comminuted metaphyseal or diaphyseal fractures, periprosthetic fractures, and fractures occurring in poor quality bone.4,8,19,24Locked plates may also be used as an alternative to dual conventional plating techniques for bicondylar tibial plateau fractures.8,28Additional indications for locked plate systems include metaphyseal fractures of long bones in which intramedullary (IM) nail xation may have a high likelihood of malalignment and for xation after corrective osteotomy procedures.8锁定钢板现行使用指征包括：复杂关节周围骨折、粉碎性干骺端或骨干骨折，假体周围骨折、较差骨质量的骨折。锁定钢板还可以代替传统双钢板技术用于双侧胫骨平台骨折。此外，使用髓内钉固定极易造成对位不良的长骨的干骺端骨折和矫正性截骨术也可使用锁定钢板。Laboratory Evaluation of Locked Plate Systems锁定钢板系统的实验室评价：Since the advent of locked plating systems, these constructs have been evaluated with varying results in a number of cadaveric models for a variety of fracture locations and patterns. In a comparison of locked plating with xed angle blade plate xation of surgical neck fractures of the proximal humerus, Siffri et al demonstrated that the locked plate provided signicantly greater stability to torsional loads and a trend toward greater stability in response to bending loads(P = 0.079).13During cyclic loading of their cadaveric specimens, the locked plate construct resulted in signicantly less loosening than their blade plate counterparts. Weinstein et al found a similar improved resistance to torsional loading with locked plating compared to angled blade plate xation of simulated 3-part proximal humerus fractures. 16 Overall, the locked plate provided almost twice the torsional resistance of the angled blade plate with the most pronounced difference noted in the specimens with the lowest bone mineral density.On the basis of their data, the authors concluded that locked plate xation of proximal humerus fractures is advantageous in the elderly, osteoporotic patients who typically sustain these fractures, potentially allowing for earlier postoperative rotational mobilization. Seide et al compared locked and unlocked plate xation for simulated proximal humerus fractures and found that locked plate xation was signicantly stiffer and provided a 64% increase in ultimate failure strength.12Cyclic loading led to xation failure in each of the specimens treated with unlocked constructs (range, 97,000 to 500,000 cycles),whereas none of the locked plate constructs failed at 1 million cycles. A similar improved xation strength of locked plate constructs compared to conventional plating techniques was demonstrated by Walsh et al in a cadaveric 2-part proximal humerus fracture model.15The authors found a 23% increase in failure strength associated with locked plate xation. Edwards et al compared the biomechanical properties of locked plate constructs and IM nails for the xation of 2-part surgical neck fractures of the proximal humerus.29The authors found that in response to varus cantilever bending, the specimens treated with locked plating had signicantly less fracture fragment displacement than those treated with IM xation. Additionally, the locked plate provided signicantly better resistance to torsional loads and was found to be overall a stiffer construct. On the basis of their data, they concluded that locked plate constructs for surgical neck fractures demonstrated superior biomechanical characteristics com pared to IM nail xation。锁定钢板系统面世以来，在尸体模型上经受了许多骨折部位和类型的评价。评价结果各式各样。在一项肱骨近端骨折锁定钢板与固定角度接骨板的对比研究中，Siffri等证明锁定钢板在扭转负荷下具有更高的稳定性，并且在弯曲负荷下趋向于更稳固。而在同样尸体标本的循环负荷下，锁定钢板较之于普通接骨板更少发生松动。Weinstein等人在类似的肱骨近端3部分骨折中，发现锁定钢板比固定角度接骨板具有类似的较强抗扭转负荷效果。总体上来讲，在最低骨矿物质密度的标本实验中，锁定钢板具有固定角度接骨板接近2倍的抗旋转负荷作用，这是二者最显著的区别。基于这些研究数据，作者推断锁定钢板对于经常遭受肱骨近端骨折的老年病人、骨质疏松病人有利，可允许术后更早的旋转运动。Seide等在模拟的肱骨近端骨折对比锁定与非锁定钢板时发现，锁定钢板刚度显著增加，并且临界衰竭强度高出64%。在循环负荷下，所有非锁定钢板治疗的试验皆以固定失败而告终（97,000-500,000循环）。而锁定钢板经受了1,000,000循环的负荷仍无一失败。Walsh 等人在尸体标本的肱骨近端2部分骨折模型试验中，证实了锁定钢板比传统钢板具有类似的更强固定能力；锁定钢板的衰竭强度高出23%。Edwards等则在肱骨近端2部分外科颈骨折中对比锁定钢板系统与髓内钉二者的固定效果。他们发现在内翻的悬吊弯曲下，采用锁定钢板治疗的标本骨折端移位更少。并且，锁定钢板能更强地对抗旋转负荷，整体构件有着更高的强度。基于这些数据，他们推断对于肱骨外科颈骨折，锁定钢板固定在生物力学上优于髓内钉固定。Recent studies have compared locked plate constructs with conventional treatment modalities for the management of distal femur fractures. Zlowodzki et al evaluated the biomechanical characteristics of the Less Invasive Stabilization System (LISS; Synthes, Paoli, PA), angled blade plate, and retrograde IM nail, in distal femur fracture xation. 17 In their cadaveric model, the locked LISS construct demonstrated greater xation strength in response to axial loading compared to both the angle blade plate and IM nail. Lower resistance to torsional loads was noted with the LISS plate xation;however, torsional load to failure for all of the tested treatment methods in this study occurred at loads much higher than those seen clinically. The same authors compared the locked LISS plating construct with a 95-degree angled blade plate for xation of distal femur fractures in specimens selected for high bone mineral density.30In this specic subset, no difference was noted in the loads to failure between the 2 xation techniques (mean load to failure: LISS 977 N; angled-blade plate,901 N). In a similar cadaveric distal femur fracture model, Higgins et al found that, compared to xation with an angled blade plate, locked plate xation resulted in signicantly less fracture fragment subsidence with cyclic loading and signicantly greater ultimate load to failure.31最近研究还在股骨远端骨折治疗中将锁定钢板与传统治疗方法进行了对比。Zlowodzki等在股骨远端骨折固定中，对微创固定系统(LISS; Synthes, Paoli, PA)、角度接骨板、逆行髓内钉三者的生物力学特性进行了评价。在他们的尸体模型中，对于轴向负荷锁定LISS系统较另外二者具有更强的固定效果；而抵抗扭转负荷能力则较弱。然而，在这项研究中所有导致固定失败的旋转负荷远远超出了临床实际所见。同样的作者在较高骨密度的股骨远端骨折固定中将锁定LISS系统与95角钢板进行了对比，结果发现在这一特定的组别中，二者的失败负荷没有差异（平均失败负荷LISS977N;角钢板901N）。在类似的股骨远端骨折尸体模型研究中Higgins等发现，与角度接骨板相比，锁定钢板固定能显著减少骨折块塌陷并且有着更高的衰竭强度。Ratcliff et al compared the mechanical stability of a laterally placed locked plate construct with a medially applied buttress plate for the xation of a simulated medial tibial plateau fracture.32Although no signicant difference was noted between xation constructs with respect to displacement secondary to cyclic loading, the medial buttress plate resulted in signicantly higher failure strength (4136 N compared to 2895 N; P , 0.05).Single lateral locked plating was compared to dual plating in the management of bicondylar tibial plateau fractures in a cadaveric model by Higgins et al.33The authors found that dual plate xation permitted less medial fragment subsidence than the isolated lateral locked plate construct. Based on their data, the authors concluded that isolated laterally placed locked plates may not be the best xation method for bicondylar tibial plateau fractures. Different results were reported by Gosling et al, in their evaluation of dual plating versus unilateral locked plating for bicond