胫骨平台后外侧骨折3种内固定方式的有限元分析

背景：如今胫骨平台骨折的研究已由起初的内外侧＂双轨道结构＂逐步转型为＂360°全方位立体结构＂,国内外学者们更关注平台后侧结构的稳定性、复位情况以及对复位后功能恢复的影响。后侧平台的内固定材料的选择仍无明确定论,存在较大争议。目的：探讨胫骨平台后外侧骨折3种内固定方式的生物力学特性。方法：通过计算机三维有限元技术,模拟胫骨平台后外侧1/2和后外侧1/4骨折。分别使用前侧2枚6.5 mm拉力螺钉、外侧4.5 mm L型钢板以及后侧3.5 mm T型钢板置入内固定骨折块。在胫骨平台中心处加载500 N纵向应力,比较3种内固定方式的生物力学状态。结果与结论：在1/2骨块模型中,前侧拉力螺钉与后侧钢板在各个方向上的位移较小,外侧钢板的位移较其他两种固定方式大。而在1/4骨块模型中,前侧拉力螺钉在各方向的位移优势更明显,后侧钢板的位移居次,外侧钢板的位移最大。1/2骨块上,前侧拉力螺钉的最大应力为36.523 MPa,外侧钢板为153.372 MPa,后侧钢板为115.922 MPa;而在骨块上的最大应力前侧拉力螺钉模型为4.309 MPa,外侧钢板为4.37 MPa,后侧钢板为3.124 MPa。1/4骨块上前侧拉力螺钉的最大应力为36.803 MPa,外侧钢板为153.336 MPa,后侧钢板为104.234 MPa;而在骨块上的最大应力前侧拉力螺钉模型为1.195 MPa,外侧钢板为0.827 MPa,后侧钢板为1.196 MPa。提示前侧拉力螺钉能够承担更大的应力,并在受到应力后位移变化较小,可提供较稳定的支持。而后侧钢板在骨块较大（1/2骨块）时,能够提供较强的稳定性,与拉力螺钉相仿;而在骨块较小（1/4骨块）时,稳定性不如前侧拉力螺钉。外侧钢板在固定胫骨平台后外侧骨折时,稳定性较差,不如前侧拉力螺钉和后侧钢板。     

Optimal configuration of a dual locking plate for femoral allograft or recycled autograft bone fixation: A finite element and biomechanical analysis

BackgroundAllografts and recycled bone autograft are commonly used for biological reconstruction. The dual locking plates fixation method has been advocated for increasing allograft stability and preventing fixation failure; however, the biomechanical properties of the various configurations of dual locking plates have not been extensively studied.MethodsIn a finite element (FE) analysis, we developed 6 patterns of different dual locking plate configurations for fixation of the mid shaft of the femur. The maximum strains were recorded for each of the 6 models then axial, bending and torsion stiffness were calculated. The FE analysis was validated the results with mechanical testing (axial compression, bending, and torsional stiffness) on a cadaveric femur.FindingsThe highest axial compression (715.41 N/mm) and lateral bending (2981.24 N/mm) was found in Model 4 (with two 10-hole locking plates placed at the medial and lateral side), while the highest torsional stiffness (193.59 N·mm /mm) was found in Model 3 (with 8- and 10-hole locking plates placed at the posterior and lateral side). Excellent agreement was found between the finite element analysis and biomechanical testing (r² = 0.98).InterpretationThe dual locking plate configuration with medial and lateral, 10-hole locking plates provided the most rigid and strongest fixation of the femur; both in terms of axial compression and lateral bending stiffness.     

Utility of cement injection to stabilize split-depression tibial plateau fracture by minimally invasive methods: A finite element analysis

BackgroundTreatment for fractures of the tibial plateau is in most cases carried out by stable fixation in order to allow early mobilization. Minimally invasive technologies such as tibioplasty or stabilization by locking plate, bone augmentation and cement filling (CF) have recently been used to treat this type of fracture. The aim of this paper was to determine the mechanical behavior of the tibial plateau by numerically modeling and by quantifying the mechanical effects on the tibia mechanical properties from injury healing.MethodsA personalized Finite Element (FE) model of the tibial plateau from a clinical case has been developed to analyze stress distribution in the tibial plateau stabilized by balloon osteoplasty and to determine the influence of the cement injected. Stress analysis was performed for different stages after surgery.FindingsJust after surgery, the maximum von Mises stresses obtained for the fractured tibia treated with and without CF were 134.9 MPa and 289.9 MPa respectively on the plate. Stress distribution showed an increase of values in the trabecular bone in the treated model with locking plate and CF and stress reduction in the cortical bone in the model treated with locking plate only.InterpretationThe computed results of stresses or displacements of the fractured models show that the cement filling of the tibial depression fracture may increase implant stability, and decrease the loss of depression reduction, while the presence of the cement in the healed model renders the load distribution uniform.     

Mechanical behavior of fixation components for periprosthetic fracture surgery

BackgroundReliable periprosthetic fracture treatment needs detailed knowledge on the mechanical behavior of the fixation components used. The holding capacity of three conventional fixation components for periprosthetic fracture treatment was systematically investigated under different loading directions.MethodsLocking compression plates were fixed to a 7 cm long part of diaphyseal fresh frozen human femur with either a single 1.7 mm cerclage cable, a 5.0 mm monocortical or a bicortical locking screw (n = 5 per group). Constructs were loaded in lateral, torsional and axial direction with respect to the bone axis in a load-to-failure test. Corresponding stress distribution around the screw holes was analyzed by finite element modeling.FindingsBoth screw fixations revealed significantly higher stiffness and ultimate strength in axial compression and torsion compared to the cerclage (all P < 0.01). Ultimate strength in lateral loading and torsion was significantly higher for bicortical screws (mean 3968 N SD 657; mean 28.8 Nm SD 5.9) compared to monocortical screws (mean 2748 N SD 585; mean 14.4 Nm SD 5.7 Nm) and cerclages (mean 3001 N SD 252; mean 3.2 Nm SD 2.0) (P ≤ 0.04). Stress distribution around the screw hole varied according to the screw type and load direction.InterpretationFixation components may be combined according to their individual advantages to achieve an optimal periprosthetic fracture fixation.     

Locking plate constructs benefit from interfragmentary lag screw fixation with decreased shear movements and more predictable fracture gap motion in simple fracture patterns

BackgroundA mechanical characterisation of lag screw fixation plus locking plate – although clinically widely used as either “mixed fixation concept” or absolutely stable fixation – is so far missing. This study aimed to evaluate the influence of an interfragmentary lag screw on the resulting motion at the fracture site of locking plate constructs using a simple fracture at the distal femur.MethodsHuman cadaver femora were in vitro loaded in torsion and axial bending-compression with and without lag screw fixation next to a locking plate fixation. In addition, two plate working lengths were tested. Interfragmentary movement was measured optically.FindingsAxial interfragmentary movement is reduced with lag screw (102 mm plate working length, 1000 N, mean): 0.28 mm versus 0.82 mm. With lag screw, the fracture gap stays closed with mean normal interfragmentary movement ≤0.03 mm. Fracture gap tends to open without lag screw: normal interfragmentary movement up to −0.29 mm. Reduction of shear interfragmentary movement was observed throughout all tested loads and groups. Mean true shear remains generally low with lag screw (≤0.42 mm) compared to without lag screw (≤1.46 mm). We also found that interfragmentary movement variance decreases with lag screw, especially for longer plate working length.InterpretationAn interfragmentary lag screw next to locking bridge plating reduces fragment motion in vitro for a simple fracture pattern and provides a sufficient tool to decrease detrimental shear movements. Prospective clinical trials with interfragmentary lag screw fixation should prove these findings in wide clinical use to treat simple fracture patterns.     

Biomechanical evaluation of different types of lateral hinge fractures in medial opening wedge high tibial osteotomy

BackgroundLateral hinge fractures are common complications in the medial opening wedge high tibial osteotomy for treatment of knee osteoarthritis. The rehabilitation protocols are decided depending on the remaining stability following these fractures. This study aimed to evaluate the biomechanical properties of different types of lateral hinge fractures in medial opening wedge high tibial osteotomy.MethodsTwenty synthetic tibia models were used as test samples. A 10-mm bone wedge was removed from the medial side of the proximal tibias to create the bone defect. The samples were then divided into 4 groups: (1) intact lateral hinge; (2) Takeuchi type I fractures; (3) type II fractures; and (4) type III fractures. After fixation with a locking plate, the stability parameters including construct stiffness, wedge displacement, and construct strength were tested under compressive forces and compared among the 4 groups.FindingsNo statistical difference was found in the construct stiffness among the 4 groups (P = 0.78). The type III fractures had the largest wedge displacement compared with the other 3 groups. The failure loads on average were significantly reduced in the type III fractures compared with those with intact hinge (P < 0.01) and in type I fractures (P = 0.04). No statistical difference was observed between the type I fractures and the intact hinge in terms of wedge displacement or failure loads.InterpretationThe type III fractures were the most unstable and patients with these fractures should be managed cautiously. Delayed weightbearing and/or additional fixation should be considered.     

锁定加压钢板与解剖钢板置入内固定治疗复杂胫骨平台骨折

背景:对于治疗复杂胫骨平台骨折,锁定钢板与普通钢板均可应用。目的:比较锁定钢板与普通解剖型钢板置入内固定治疗复杂胫骨平台骨折疗效的差异。方法:2007年6月至2010年6月应用胫骨近端钢板治疗复杂胫骨平台骨折118例,其中锁定加压钢板46例,解剖钢板72例。比较两种钢板置入内固定治疗复杂胫骨平台骨折的愈合时间及膝关节功能恢复情况。结果与结论:所有胫骨平台骨折均愈合,骨折愈合时间为10-25周,锁定钢板组平均14周,解剖钢板组平均16周;两组差异有显著性意义(P<0.01)。两组内固定后各有2例因开放性骨折切口感染,运用抗生素及伤口换药后愈合,1例出现筋膜间室综合征(解剖钢板组,内固定后),经切开减压后渐愈。解剖钢板组出现轻度膝内翻2例,锁定钢板组出现轻度膝内翻1例。按Karlstrom评估标准,锁定钢板组优良率为93%,解剖钢板组优良率为79%,锁定钢板组疗效优良率明显优于解剖钢板组(P<0.05)。可见对于治疗复杂胫骨平台骨折,锁定钢板比普通钢板有更多优势。     

三种固定方式修复胫骨平台后外侧骨折的生物力学比较

背景：胫骨平台后外侧骨折修复方案包括后侧钢板螺钉、外侧钢板螺钉和前后拉力螺钉内固定;选择何种内固定方法主要是靠医师的临床经验,研究结果也大多是临床报道,缺乏力学实验的依据。目的：从生物力学角度比较外侧钢板螺钉组、后侧钢板螺钉组、前后拉力螺钉组3种固定方式修复胫骨平台后外侧骨折的生物力学变化。方法：采用6具成年男性防腐尸体胫骨标本共12个进行干骺端骨密度测定。电动摆锯建立胫骨平台后外侧1/2骨折模型,模型随机分3组进行前后拉力螺钉固定、外侧钢板螺钉固定、后侧钢板螺钉固定。利用有限元法和生物力学方法在250,500,1000 N的轴向载荷下测试骨折块的轴向位移值及最大位移值分布区。结果与结论：3组标本干骺端平均骨密度差异无显著性意义（P〉0.05）。在轴向载荷为250 N时,有限元实验中骨折块的位移值,前后拉力螺钉组最小,为0.013521 mm;后侧钢板螺钉组居中,为0.016991 mm;外侧钢板螺钉组最大,为0.138200 mm,在500,1000 N时情况类似。实验生物力学结果显示,前后拉力螺钉组的位移值明显小于外侧钢板螺钉组和后侧拉力螺钉组（P〈0.05）;后侧钢板螺钉组与外侧钢板螺钉组比较差异无显著性意义（P〉0.05）,两种测试方法最大位移值分布区域都在近侧胫腓关节交界区。提示在生物力学稳定性方面,前后拉力螺钉组最具优势,外侧钢板螺钉组较差。临床可以考虑将前后拉力螺钉固定作为修复胫骨平台后外侧骨折的首选方案。     

Comparison of forces generated using compression plating versus a magnetic lengthening nail in a sawbones femur model

BackgroundThe purpose of this study is to compare compression generated by a Precice magnetic lengthening intramedullary nail and a 5.0 mm limited contact dynamic compression plate.MethodsTransverse osteotomy sites were created in the femoral shaft of ten Sawbones fourth generation composite femurs. Antegrade 10-degree trochanteric Precice nails and 8-hole, 5.0 mm plates were used for fixation. The plates were compressed by placing a neutral screw and three eccentrically drilled compression screws on alternating sides of the osteotomy. Average compression and distribution of compression were compared, and P-values <0.05 were considered statistically significant.FindingsThe Precice nail generated an average of 2.38 megapascal across the osteotomy sites. The plate generated an average of 0.70 megapascal (P < 0.001) with the initial compression screw, 0.93 megapascal (P < 0.001) after the second screw, and 1.04 megapascal (p < 0.001) after the final screw. The distribution of compression was assessed utilizing a polar transformation to compare pressure values. We found that the distribution of compression was more circumferentially uniform in the Precice nail group (P = 0.046).InterpretationThis study demonstrates that an electromagnetic intramedullary device is capable of generating significantly higher compression, in a more uniform distribution, than a 5.0 mm limited contact dynamic compression plate in a Sawbones model. The results indicate that electromagnetic intramedullary nail systems may be an ideal alternative to compression plating for treatment of at-risk fractures, nonunions, delayed unions, and intercalary allograft reconstruction.     

不同内固定物治疗胫骨平台后内侧骨折的生物力学分析

背景：胫骨平台后内侧骨折的治疗较困难,容易出现因骨折固定方式选择不当导致骨折再次移位、骨不连、内固定失效及关节功能活动障碍等并发症。目的：分析3种胫骨平台后内侧骨折不同固定方法的生物力学效果。方法：27具新鲜骨标本,制成胫骨平台后内侧骨折模型,分别制成正常组,双钢板固定组,T形钢板固定组,拉力螺钉固定组。对以上3组进行压力、载荷一位移、应力强度、刚度和旋转性能测试。结果与结论：双钢板固定组载荷一位移显著小于T型钢板固定组和拉力螺钉固定组,双钢板固定组轴向刚度、水平剪切刚度及转矩扭角变化,均显著大于T型钢板固定组和拉力螺钉固定组。提示胫骨平台后内侧骨折双钢板固定较其他2种方法更具有生物力学上的稳定性。     

Selection of internal fixation method for femoral intertrochanteric fractures using a finite element method

BACKGROUNDFailure to fix unstable intertrochanteric fractures impairs return to daily activities.AIMTo simulate five different internal fixation methods for unstable proximal femoral fractures.METHODSA three-dimensional model of the femur was established from sectional computed tomography images, and an internal fixation model was established. Finite element analysis of the femur model was established, and three intertrochanteric fracture models, medial defect, lateral defect, and medial-lateral defects, were simulated. Displacement and stress distribution after fixation with a proximal femoral anti-rotation intramedullary nail (PFNA), integrated dual-screw fixation (ITN), PFNA + wire, PFNA + plate, and PFNA + wire + plate were compared during daily activities.RESULTSThe maximum displacement and stress of PFNA and ITN were 3.51 mm/473 MPa and 2.80 mm/588 MPa for medial defects; 2.55 mm/288 MPa and 2.10 mm/307 MPa for lateral defects; and 3.84 mm/653 MPa and 3.44 mm/641 MPa for medial-lateral defects, respectively. For medial-lateral defects, reconstructing the medial side alone changed the maximum displacement and stress to 2.79 mm/515 MPa; reconstructing the lateral side changed them to 3.72 mm/608 MPa, when both sides were reconstructed, they changed to 2.42 mm/309 MPa.CONCLUSIONFor medial defects, intramedullary fixation would allow early low-intensity rehabilitation exercise, and ITN rather than PFNA reduces the risk of varus and cut-out; for lateral wall defects or weakness, intramedullary fixation allows higher-intensity rehabilitation exercise, and ITN reduces the risk of varus. For both medial and lateral defects, intramedullary fixation alone will not allow early functional exercise, but locating lateral or medial reconstruction will. For defects in both the inner and outer sides, if reconstruction cannot be completed, ITN is more stable.     

锁定加压钢板置入内固定治疗胫骨骨折的力学分析

背景：锁定加压钢板结合了传统钢板和支架原理,即头部有锁定螺纹的螺钉和钢板锁钉孔构成的内固定支架锁定单元,又有传统螺钉和动力加压孔构成的内固定支架加压单元,在骨折的内固定治疗方面具有很多优势。目的：分析锁定加压钢板置入内固定治疗胫骨骨折的生物力学特点,以及在胫骨骨折治疗中的疗效。方法：锁定加压钢板是依靠钢板与螺钉的成角稳定性和螺钉与骨之间的把持力来实现骨折内固定的。骨髓腔细小时应避免螺钉尖端损伤近端皮质的骨螺纹,应更换为双皮质自攻螺钉至少在对侧骨皮质获得把持力。骨质疏松植入螺钉,由于单皮质骨螺钉产生的工作长度减少,在所有骨折块均使用双皮质自攻螺钉,以提高螺钉工作长度。当长骨轴线与钢板对线不良时,要么打入长自攻螺钉,要么改变角度打入标准螺钉。锁定加压钢板应选择适宜的长度,钢板的长度取决钢板跨越比和钢板螺钉密度,钢板与螺钉间的应力还受螺钉数量和位置的影响。结果与结论：锁定加压钢板置入内固定可应用于骨干或干骺端的简单骨折、粉碎性骨折、关节内及关节周围骨折、骨折延迟愈合、闭合或开放截骨术和不适合髓内钉固定的骨干骨折,对于骨质疏松骨折和假体周围骨折的内固定有很好的成角稳定性和把持力。锁定加压钢板置入内固定治疗胫骨骨干骨折均取得满意的疗效,符合生物力学固定原理。需要术者熟练掌握锁定加压钢板的内固定技术,避免由于失误导致内固定的失败。     

Increased stability by a novel femoral neck interlocking plate compared to conventional fixation methods. A biomechanical study in synthetic bone

BackgroundStable fixation promotes union in the common femoral neck fractures, but high non-union rates due to fixation failure remain with traditional fixations. To enhance stability, a plate interlocking pins, but without further fixation to femur has been developed. To our knowledge, no comparison to other conventional fixation methods has been performed. We tested the hypothesis that the novel implant biomechanically leads to a more stable femoral neck fixation.MethodsFifty synthetic femurs with a cervical wedge osteotomy were allocated to intervention with three hook-pins interlocked in a plate (Hansson Pinloc® System) or standard fixations with a two-hole Dynamic Hip Screw® plate with an anti-rotational screw, three cannulated screws (ASNIS® III) or two screws (Olmed® or Cannulated Hip Screws®). Quasi-static non-destructive torsion around the neck, anteroposterior bending and vertical compression were tested to detect stiffness. The specimen's deformation was evaluated after cyclic compression simulating weight-bearing. Local deformation of implant channels was measured. Fixation failure was defined by fissure formation.FindingsCompared to the conventional implants all together, the interlocked pins enhanced mean stiffness 130% in torsion and 33% in bending (P < 0.001), while compressive stability was increased by a reduced deformation of 62% in average of the global test specimen and 95% decreased local implant channel deformation after cycling (P < 0.001). In comparisons with each of the standard fixations the interlocking pins revealed no signs of adverse effects.InterpretationThe novel femoral neck interlocking plate allowed dynamic compression and improved multi-directional stability compared to the traditional fixations.     

A novel internal fixation method for open book injuries of the pubic symphysis— A biomechanical analysis

BackgroundPelvic fractures in adults are common injuries and account for up to 3.64% of all fractures. Usually, the treatment of open book injuries (Types B1.1 and B1.2 AO-Classification) is open reduction and plate stabilization using dynamic compression plates, with or without interlocking screws. These implants seem to enhance the outcome of such injuries, but also variety of complications occurs. To reduce complications and achieve appropriate reduction and stabilization, this study compared established stabilization techniques to a novel minimally invasive internal fixation method using an internal fixator system that is already being utilized for spinal fractures.MethodsThis study was performed on 32 composite pelvises in a bilateral stance biomechanical model. The pelvises were variously stabilized with an internal fixator, a 4.5 mm dynamic compression plate and a 3.5 mm symphyseal locking dynamic compression plate. The contact area and loading forces were assessed by a sensor film inside the symphyseal gap.FindingsThis study showed significantly greater reduction and loading capabilities of the internal fixator compared to the other implants (p < 0.05). There was also significantly greater contact area with the use of an internal fixator compared to the other implants (p < 0.05). The 3.5 mm interlocking plate showed significantly greater contact area compared to the 4.5 mm plate (p < 0.05).InterpretationThe internal fixator that is already proven in spinal surgery is biomechanically superior to conventional implants used in pelvic surgery. The contact area analysis furthermore showed a more physiological loading pattern, which can improve ligamentous healing in a clinical context.     

微创锁定钢板治疗胫骨平台Ⅴ、Ⅵ型骨折

【目的】总结微创锁定钢板治疗复杂胫骨平台骨折的临床疗效。【方法】本院从2006年3月至2008年11月对11例胫骨平台Ⅴ、Ⅵ型骨折行切开复位,外侧锁定板内固定术,必要时配合内侧钢板固定,其中Ⅴ型5例,Ⅵ型6例,骨缺损较多者给予植骨,术后早期功能锻炼。【结果】所有患者术后骨折一期愈合,骨折对位对线良好,膝关节屈曲110°～130°,膝关节功能用HSS平分法80～96分,平均90．4。【结论】微创锁定钢板治疗胫骨平台Ⅴ、Ⅵ型骨折,具有手术创伤小,骨折愈合快,功能恢复好的优点。     

外侧锁定联合内侧支持钢板与双支持钢板内固定修复胫骨平台骨折的比较

背景：胫骨平台骨折采用单侧支持钢板容易形成偏心支撑,易导致成角畸形,而若仅用外侧支持钢板又容易出现膝关节内翻畸形。目的：比较双切口外侧锁定钢板联合内侧支持钢板与双支持钢板内固定修复复杂胫骨平台骨折的临床及影像学效果。方法：回顾性分析2009年3月至2013年11月收治86例复杂胫骨平台骨折患者的临床资料。根据其内固定方式分为2组,外锁定内支持组采用外侧锁定钢板固定骨折情况相对较复杂及粉碎程度较重的外侧,内侧采用支撑钢板;内外支持组则内外侧均采用支撑钢板固定。术后随访2年,对比两种内固定方式的临床及影像学效果。结果与结论：所有随访患者创口均Ⅰ期愈合,骨折均获得骨性愈合。两组患者的手术时间、上止血带时间及术中出血量比较差异均无显著性意义（P〉0.05）。术后随访发现,除完全负重时间外锁定内支持组明显早于双支持钢板组外（P〈0.05）,两组骨折愈合时间、膝关节功能评分、膝关节活动度、术后胫骨平台内翻角、胫骨平台后倾及术后1年胫骨平台内翻角、胫骨平台后倾差异均无显著性意义（P〉0.05）。提示双切口双钢板置入内固定修复胫骨平台骨折具有良好的临床及影像学效果,与双支持钢板相比,外侧锁定钢板联合内侧支持钢板在完全负重时间上更具优势。     

Biomechanical study of Proximal humeral fracture fixation: Locking plate with medial support screw vs. locking plate with intramedullary fibular graft

BackgroundThe purpose of this study was to evaluate the biomechanical properties of two different fixation constructs in varus collapse proximal humerus fracture, locking plate with medial support screw and locking plate with intramedullary fibular graft.MethodsWe used 8 pairs of undamaged fresh-frozen humen cadaveric humeri and fibula from patients ranging in age from 62 to 81 years. We simulated a proximal humerus fracture with medial comminution using wedge shaped osteotomy. One group was fixed with locking plate with medial support screws, the other group with locking plate with intramedullary fibular graft. Biomechanical test was carried out using servohydraulic material testing system. We measured displacement of specimens under cyclic load test, maximum failure load, initial stiffness, and mode of failure under increasing load test.FindingsUnder cyclic loading, the displacement of the specimen was significantly less in the locking plate with fibular strut graft group than in the locking plate with medial support screws group. (p = 0.012) Under increasing load test, the Locking plate with fibular strut graft group showed higher values in both maximum failure load and initial stiffness than the Locking plate with medial support screws group, and this was statistically significant. (p = 0.012, p = 0.001).InterpretationIn biomechanical study, the locking plate with fibular strut graft showed significantly better results in all of the maximum failure load, initial stiffness, and gap depletion compared to the locking plate with medial support screws.Level of evidenceLevel IV.     

Two reconstruction plates provide superior stability of displaced midshaft clavicle fractures in comparison to single plating – A biomechanical study

BackgroundDisplaced midshaft fractures are the most common surgically treated clavicle fractures. However, they are associated with high complication rates following plating due to fixation failure in terms of plate breakage, screw breakage and/or screw loosening. The aim of this study was to compare the biomechanical competence of three different plating techniques for fixation of displaced midshaft clavicle fractures.MethodsDisplaced midshaft fractures type 2B according to the Robinson classification were simulated by standardized osteotomy gap in 18 synthetic clavicles, assigned to three groups (n = 6) for plating with either superiorly placed Dynamic Compression Plate (width/thickness 11.0/4.0 mm), locked Superior Anterior Clavicle Locking Compression Plate (width/thickness 10.2/2.0 mm), or two non-locked Reconstruction Plates placed superiorly and anteriorly (width/thickness 10.0/2.8 mm). Each specimen was cyclically tested at 3 Hz under craniocaudal cantilever bending, superimposed with torsion around the shaft axis over 720′000 cycles or until failure occurred. The latter was defined by plate breakage, screw breakage or screw loosening.FindingsInitial construct stiffness (N/mm) and cycles to failure in group Reconstruction Plates (22.30 ± 4.07; 712′778 ± 17′691) were significantly higher compared with both groups Compression Plate (12.53 ± 2.09; 348′541 ± 212′941) and Locking Plate (4.19 ± 0.46; 19′536 ± 3′586), p ≤ 0.019. In addition, these two outcomes were significantly higher in group Compression Plate versus Locking Plate, p ≤ 0.029.InterpretationDouble plating of unstable midshaft clavicle fractures with reconstruction plates seems to provide superior fixation stability under dynamic loading, when compared to single compression or locked plating, whereas the latter is associated with inferior performance.     

胫骨近端锁定加压钢板治疗胫骨平台骨折32例疗效分析

[目的]探讨胫骨近端锁定钢板治疗胫骨平台骨折的临床疗效分析。[方法]分析2006年12月至2008年8月32例采用胫骨近端锁定钢板固定胫骨平台骨折病例,评价胫骨近端锁定钢板对胫骨平台骨折治疗效果。本组32例,男20例,女12例,平均年龄42岁。其中车祸28例,摔伤4例;B2型骨折6例,B3型12例,C1型10例,C2型4例。[结果]本组32例患者均获随访,随访时间3～18个月,平均10．5个月。所有患者均骨性愈合。Sanders膝关节评分结果：优26例,良5例,可1例。优良率96．87％。[结论]胫骨近端锁定钢板治疗胫骨平台骨折临床疗效满意,固定效果好,手术损伤小,患者术后功能恢复好。     

Screws with larger core diameter and lower thread pitch increase the stability of locked plating in osteoporotic proximal humeral fractures

BackgroundLittle is known about the screw design as a factor for stability of the bone-implant interface in locking plate fixation of proximal humeral fractures. Aim of the present study was to analyze if locking screws with a large core diameter and a low thread pitch provide increased stability when compared to conventional locking screws.Methods3-Part proximal humeral fractures were created in ten pairs of osteoporotic human cadaveric humeri and fixed with a locking plate. Head fixation was performed with screws with a large core diameter (soft bone screws) in one humerus and with conventional cancellous locking screws in the other humerus of each donor. Specimens were loaded in the varus bending position. Stiffness, failure loads, plate bending and motion at the bone-implant interface were evaluated using mechanical sensors and an optical motion capture system.FindingsThe stiffness of the construct for the soft bone screws was 299.8 N/mm (IR, 72.1 N/mm) and 203.9 N/mm (IR, 37.3 N/mm) for the conventional locking screws (p = 0.005). Plate bending did not differ between the two groups. Motion at the bone-implant interface was significantly reduced in the soft bone screw group (p < 0.05). The median load-to-failure was significantly higher in the soft bone screw group (358 N vs. 313 N; p = 0.012).InterpretationThe use of soft bone screws is associated with less motion at the bone-implant interface and therefore greater fixation strength when compared to fixation with conventional locking screws. Clinical studies are needed to prove these biomechanical findings in the in vivo situation.Level of evidence: Controlled laboratory study.