【作者】 叶伟雄；

【导师】 梁伟国；

【作者基本信息】 暨南大学 ， 外科学， 2010， 硕士

【摘要】 目的胫骨远端骨折在全身骨折占比例较大。胫骨下段表面形态不规则,周围软组织覆盖少及其生物力学的复杂性使临床治疗难度较大。近年来,应用外侧解剖型锁定钢板治疗胫骨远端骨折已被广泛采用,使间接复位和桥式固定等微创钢板技术(MIPO)得以实施。第一代锁定钢板的锁定螺钉方向在生产时是预先设定的,不能在安装时按需调节,严重影响固定效果,甚至出现固定失效。为了解决上述问题,我们自行设计了种胫骨下段可调角度自锁式解剖型钢板。本研究的目的是测试这种胫骨下段可调角度自锁式解剖型钢板的生物力学性能,为临床应用提供科学依据。方法根据国人胫骨下段的解剖特征,自行研制胫骨下段可调角度自锁式解剖型钢板。钢板为汤匙状,远端宽大,近段呈长干状。钢板的远段向前扭转,钢板的最大扭转角度为80°,扭转段为12cm。远端膨大处为2.4×2.4cm2,近段干部宽度为1.7cm。可调锁定螺孔位于钢板的临近关节端,有三个,呈品字形排列。于钢板的骨干段,可调锁定螺孔与普通锁定螺孔呈间隔分布。螺孔俯视呈圆形,切面剖视螺孔区呈鼓形中空,上开口和下开口直径均为8mm,中间膨大处直径为9.2mm。角度锁定环位于钢板的可调锁定螺孔内。俯视为圆环形,圆环有一“C”形缺口,于圆环体正面有三个呈“品”字位分布的小凹,各小凹及“C”形缺口互相相隔90°。锁定环的剖视切面呈无底的桶状,外壁为无特殊处理光面,内壁为螺纹状,螺纹轴心与桶环外壁轴心有10°偏角。锁定环在钢板螺孔内被螺孔上、下小开口扣住,锁定环外径与螺孔的鼓形内径精确匹配。锁定环上的缺口和环体上的三个小凹可与角度调节套筒远端的四个齿突精确匹配,角度调节套筒带动锁定环在钢板螺孔内旋转,使锁定环的锁定方向发生改变。当锁定螺钉上紧时,锁定环小缺口设计可以允许锁定环膨大,与钢板螺孔鼓形中空部分紧密接触,产生巨大摩擦力,使螺钉角度被锁定。锁定环可以在钢板的锁定螺孔内最大侧旋5°,锁定环的螺纹轴心10°偏心角度设计可以允许螺钉调节角度加大,使得锁定螺钉的可选角度达30°。选用配对尸体胫骨标本制作骨折内固定模型。设计胫骨截骨平面分别位于骨干与远端干骺部交界处(A042与43段交界),以及其上方10mm水平,造成宽10mm的骨缺损区。全部配对的尸体胫骨标本分A、B两组,每组6例。左右侧随机分入两组中。在A组安装普通解剖型锁定钢板,在B组安装可调角度自锁式解剖型钢板。安装钢板后,分别于预先设计的截骨线上截骨,制作成一极度不稳定的A型骨折,使两骨折块之间的应力仅通过内固定物传递。测试在858 MiniBionix试验机上进行。先对两组内固定模型分别进行轴向压缩、四点弯曲和扭转载荷下的非破坏性试验。轴向压缩：以5N/S的速度加载至500N；四点弯曲：跨距为12cm,加载间距为4cm,以5N/S的速度加载至300N；扭转：以0.1°/S的速度加载至5Nm。每次测试前均进行3次最大载荷10%的预加载。每组各抽两个配对的内固定模型分别进行压缩、四点弯曲和扭转破坏强度试验,加载速度同上。选用SPSS 13.0统计软件,行同具尸体左右侧胫骨内固定模型测量数据的配对t检验,以P<0.05为有统计学意义。结果压缩刚度：A组557.53±20.72 N/mm,B组562.80±28.26 N/mm；四点弯曲刚度：A组268.02±36.77 N/mm,B组265.76±27.21 N/mm;扭转刚度：A组0.28±0.01 Nm/deg,B组0.29±0.02 Nm/deg。A、B两组三项测试指标均无统计学差异(P>0.05)。结论自行研制的胫骨下段自锁式解剖型钢板与国人胫骨下段形态更匹配。其可调锁定螺孔及角度锁定环的设计使锁定螺钉的锁定方向可根据骨折的形态作调整,确保固定的稳定性,弥补了普通锁定钢板的在临床应用的局限性。生物力学测试证实胫骨下段可调角度自锁式解剖型钢板与普通胫骨下段解剖型锁定钢板的生物力学性能相当。更多还原

【Abstract】 ObjectiveDistal tibial fractures account for certain proportion of overall fractures. Treatment for distal tibial fractures is difficult due to its irregular anatomical morphology, poor soft tissue envelope and complicated biomechanics. In resent years, application of lateral anatomical locking plate for the treatment of this kind of fractures is becoming more popular, which benefits minimally invasive plating osteosynthesis (MIPO). But the screw paths of first generation locking plate are predetermined by the manufacturers, and are not able to be regulated during assembly, which severely influents stability of fixation and even lead to failure of fixation. For this reason we have designed a polyaxial self-locking anatomical plate of distal tibia. The purpose of this study is to evaluate biomechanical properties of this polyaxial self-locking anatomical plate and offer scientific evidence for clinical application.MethodAccording to morphologic characteristics of distal tibiae of domestic people, a polyaxial self-locking anatomical plate for distal tibia was designed. The plate is spoon-liked with a flare distal part and a long- stem proximal part. The distal part of the plate twists anteriorly with the largest twisting angle of 80°and 12cm twisting segment. Distal part of the plate is 2.4x2.4cm2 in dimension. The proximal part of the plate is 1.7cm wide. Three polyaxial holes are located at distal part of the plate which are distributed triangularly. In proximal stem part of the plate polyaxial holes are distributed separately each other with common locking holes. Top view of the polyaxial hole is round shape. Cross section of the polyaxial hole is concave tympaniform with upper and lower diameter of 8mm and the largest middle diameter of 9.2mm. The polyaxial self-locking bushing is within the polyaxial hole, which is round shape in top view with a C-shaped defect. On the obverse surface of the bushing there are three triangularly distributed small concaves which are separated every 90°ach other together with the C-shaped defect. Cross section of the polyaxial self-locking bushing is bucket-shape with polish outer surface and threaded inner surface, which the inner axis is intersected with the outer axis at 10°. The polyaxial bushing is clasped by the upper and lower outlets of the polyaxial hole of the plate and is precisely fit with the inner concave surface of the polyaxial hole. The C-shaped defect of the polyaxial bushing and the three concaves on its obverse surface are precisely fit with the four dental processes on the tip of the polyaxial regulating sleeve which drives the polyaxial bushing rotating in the polyaxial hole to regulate the locking angle of the locking screw. Once the locking screw is tightened, the polyaxial self-locking bushing is expanded and snugly engaged with the concave surface of the polyaxial hole, so that strong friction is produced to fix locking angle of the screw. The polyaxial bushing can be maximally laterally rotated for 5°and the 10°eccentric angle of its inner thread axis can increase angular regulation amplitude for locking screw up to 30°. Paired cadaver tibiae were used to make fracture fixation models. The osteotomy levels were designed at the transition of segment 42 and 43 according to AO classification and 10mm above it, so that 10mm bone defect was made. All paired cadaver tibiae were divided into group A and B with 6 in each group. Left and right tibiae were randomly distributed into two groups. In group A common anatomical locking plates were assembled and in group B polyaxial self-locking anatomical plates were assembled. After assembly osteotomies were performed and a highly unstable type-A fracture was produced, with the implant alone transferring all loads. The biomechanical tests were performed using 858 Mini Bionix testing machine. In the first stage non-destructive tests were performed in both groups, including axial loading,4-point bending and torsional loading. In axial loading maximum 500N was loaded at a rate of 5N/S. In 4-point bending maximum 300N was loaded at a rate of 5N/S. In torsional loading maximum 5Nm was loaded at a rate of 0.1°/S. The constructs were preloaded to 10% of the maximum load before every test. In the second stage two pairs of constructs from two groups were selected for destructive test of axial loading,4-point bending, or torsional loading with the same loading rates. SPSS 13.0 software was used for statistical analysis, in which paired t test was performed to compare data from left and right tibial models of the same cadaver. All differences in comparisons were considered statistically significantly different at P<0.05.ResultsCompression stiffness of group A was 557.53±20.72 N/mm, and group B was 562.80±28.26 N/mm.4-point bending stiffness of group A was 268.02±36.77 N/mm, and group B was 265.76±27.21 N/mm. Torsional stiffness of group A was 0.28±0.01 Nm/deg, and group B was 0.29±0.02 Nm/deg. All differences of two groups in three tests had no statistical significance. ConclusionsSelf-designed polyaxial self-locking anatomical plate of distal tibia is better fit for the tibial morphology of domestic people. The design of polyaxial hole and polyaxial self-locking bushing can make it possible for locking screw to regulate its locking angle according to the fracture morphology, which can guarantee stability of internal fixation and make up for clinical limitations of common anatomical locking plate. Biomechanical tests have confirmed that biomechanical properties of polyaxial self-locking anatomical plate is equivalent to those of common anatomical locking plate.更多还原