基于断裂力学探讨骨密度影响老年股骨颈骨折的有限元分析

发布时间：2018-09-17 14:12

【摘要】：目的1.通过临床前瞻性分析不同骨密度与老年股骨颈骨折类型及骨折程度的关系,找出骨密度对股骨颈骨折影响的规律,是否可有效预测骨折类型和骨折程度,为预治骨折提供临床依据和方法。2.为了更好的验证骨密度对老年股骨颈骨折类型和破裂程度的影响,建立具有不同骨密度属性且更加贴近真实人体生物力学结构的股骨近端三维有限元模型,利用有限元软件进行断裂力学实验,验证对比两个模型之间的断裂类型、破坏程度等断裂力学结果,得出不同材料属性影响骨折力学变化的规律,为老年疏松性股骨颈骨折的生物力学机制研究打下实验基础。方法1.临床研究选取自2016年7月至2017年2月期间入住广州中医药大学第一附属医院创伤骨科老年股骨颈骨折病人50例,入院后经DXA骨密度测定仪行腰椎骨密度测定,分别设立 A 组(T-Score≤-2.5g/cm2)和 B 组(T-Score-2.5g/cm2),每组 25 人(25髋),男24例,女26例,年龄60-91岁,平均年龄(76.38±9.57)岁。均为闭合性骨折,左髋20例,右髋30例。经髋部X线、CT检查确诊骨折分型(Garden分型),记录患者年龄、性别、受伤侧、骨折分型和骨密度等,利用SPSS17.0软件进行统计学分析,分析骨密度与年龄、性别、受伤侧之间的关系,以及骨密度对骨折类型影响的关系。2.实验研究临床收集1例符合条件老年股骨颈骨折病人的双侧髋关节CT影像数据,用DICOM格式数据保存,利用有限元Mimics15.0软件进行区域增长、腔隙填充等步骤创建健侧股骨近端有限元模型,然后导入Hyermeshl3.0软件四面体网格划分,分别用两种不同骨密度材料属性对模型赋值(C1模型:整体赋值密质骨材料属性;C2模型:赋值松质骨、密质骨材料属性,即骨质疏松模型),生成两个贴近真实人体生理特性和力学结构的股骨近端有限元模型。设置失效参数、界面属性、分析步、边界约束与载荷后,再导入有限元后处理软件LS-DYNA计算,得到基于应力-应变曲线关系的股骨颈骨折断裂模型,并跟临床真实骨折线验证比对,观察对比两种模型断裂时的应力应变、裂纹扩展走向和骨折分型情况。结果1.A、B组平均年龄分别为:(81.7±8.12)岁、(71.2±8.09)岁,根据组间t检验分析,t=-4.520,P0.05,具有统计学意义;A、B组平均骨密度分别为:(-3.7±0.54)g/cm2、(-1.58士 1.18)g/cm2,根据组间 t 检验分析,t=8.399,P0.05,具有统计学意义。表明两组骨密度阈值设定合理,具有可比性,且骨密度与年龄呈正相关。2.A组:股骨颈骨折Garden Ⅰ、11型8例,Garden Ⅲ、Ⅳ型17例;B组:Garden Ⅰ、11型15例,Garden Ⅲ、Ⅳ型10例。不同骨密度组间骨折分型比例有一定差异,经X2检验,X2=3.945,P=0.0470.05,具有统计学意义。表明骨密度可影响骨折类型,一定程度上预测骨折类型和严重程度,且A组骨折线总体上比B组更平整规则。3.根据有限元软件建立了两种不同骨密度材料属性的股骨近端三维有限元模型和股骨颈骨折断裂模型,并得到有效验证。4.C1、C2模型骨折时裂纹扩展、裂纹走向不完全一致,且C1模型裂纹扩展、裂纹走向比C2模型更平整规则,这与临床研究结果非常相似。5.在同样边界、方向、载荷和单位时间下,C2模型所受等效应力明显比C1模型大,并且C2模型破裂严重。说明低密度骨骼更容易骨折或破裂,且破裂程度严重。结论1.通过有限元断裂力学分析,基于临床数据的股骨颈骨折的三维有限元模型建立真实可靠,可以很好的模拟股骨颈骨折断裂情况,动态下直观还原股骨颈骨折全过程,并可行断裂力学分析,为不同外力下致股骨颈骨折分型的力学机制研究提供实验基础。2.骨密度可有效影响骨质应力应变力学特性,一定程度上可影响老年股骨颈骨折类型,预判股骨颈骨折类型和破裂程度,为防治临床髋部骨折提供依据和方法。
[Abstract]:Objective 1. To analyze the relationship between different bone mineral density (BMD) and the type and degree of femoral neck fracture in the elderly, find out the regularity of BMD's influence on femoral neck fracture, and whether it can effectively predict the type and degree of fracture, so as to provide clinical evidence and methods for the treatment of fractures. 2. To better verify the effect of BMD on femoral neck fracture in the elderly. The three-dimensional finite element model of proximal femur with different bone mineral density attributes and more close to the biomechanical structure of real human body is established. Fracture mechanics experiments are carried out by using finite element software to verify and compare the fracture mechanics results of the two models, such as fracture types and degree of failure. Methods 1. 50 elderly patients with femoral neck fracture admitted to the Department of Traumatic Orthopedics, First Affiliated Hospital of Guangzhou University of Traditional Chinese Medicine from July 2016 to February 2017 were selected for clinical study. After admission, they were performed with DXA bone mineral density analyzer. Bone mineral density (BMD) of lumbar spine was measured in group A (T-Score < 2.5g/cm 2) and group B (T-Score-2.5g/cm 2). Each group consisted of 25 patients (25 hips), 24 males and 26 females, aged 60-91, with an average age of 76.38 [9.57] years. All of them were closed fractures, 20 left hips and 30 right hips. SPSS17.0 software was used to analyze the relationship between bone mineral density and age, sex, injured side, and the effect of bone mineral density on fracture type. 2. The data of bilateral hip CT images of a eligible elderly patient with femoral neck fracture were collected and analyzed in DICOM format. The data were saved and the finite element model of the proximal femur was created by using the finite element software Mimics 15.0. Then the tetrahedron mesh of Hyermeshl 3.0 was imported to divide the data. Two different properties of BMD materials were used to assign values to the model (C1 model: whole assigned dense bone material properties; C2 model: assigned cancellous material properties; C2 model: assigned cancellous material properties). Two finite element models of proximal femur, which are close to the physical and mechanical properties of human body, are generated. Failure parameters, interface properties, analysis steps, boundary constraints and loads are set up, and then the finite element post-processing software LS-DYNA is imported to calculate the femur based on the stress-strain curve. Results The average age of group A and B were (81.7 +8.12) and (71.2 +8.09) respectively. According to the t test analysis, t = - 4.520, P 0.05, there was significant difference between the two models. According to the t-test analysis, t = 8.399, P 0.05, there was statistical significance. The results showed that the thresholds of bone mineral density of the two groups were reasonable and comparable, and bone mineral density was positively correlated with age. 2. Group A: Femoral neck fracture Garden I, 11 in 8 cases, Garden III, IV in 17 cases. There were some differences in the fracture classification ratio among different BMD groups. The results showed that BMD could influence the fracture type and predict the fracture type and severity to some extent. The fracture line of group A was more smooth and regular than that of group B. 3. According to the finite element software, the fracture line of group A was established. Two kinds of three-dimensional finite element model of proximal femur and fracture model of femoral neck fracture with different BMD attributes were established and validated effectively.4.C1 and C2 models showed inconsistent crack propagation and crack orientation when they were fractured. The equivalent stress of C2 model is obviously larger than that of C1 model under the condition of sample boundary, direction, load and unit time, and the fracture of C2 model is more serious. It can simulate the fracture of femoral neck well, visualize the whole process of femoral neck fracture dynamically, and provide experimental basis for the study of mechanical mechanism of femoral neck fracture classification under different external forces. 2. Bone mineral density can effectively affect the mechanical characteristics of bone stress and strain, and to a certain extent, it can affect the elderly. The type of femoral neck fracture and the degree of fracture can be predicted to provide basis and method for prevention and treatment of hip fracture.
【学位授予单位】：广州中医药大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R683

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