Three dimensional finite element analysis of anatomic distal radius Nitinol memory connector treating distal radius fracture

To study the memory biomechanical character of anatomic distal radius Nitinol memory connec-tor ( DRMC ) in treating distal radius fracture. Methods: Establishing three dimensional model and finite element anal-ysis, we calculated the stress in and around the fracture faces when distal radius fracture was fixated with DRMC. Re-suits: Axial holding stress produced by holding part of DRMC on distal radius was 14.66 MPa. The maximum stress of holding part was 40 - 70 MPa, the minimum stress was 3 - 7 MPa, and the stress of compression part was 20 - 40 MPa.Conclusion: The distribution of stress produced by DRMC around the fracture line is reasonable, and axial holding stress can help stabilize fracture during earlier period. The existence of longitudal compression and memory effect can transfer fixated disused section into developed section and enhance fracture healing.     

Stress analysis of three-dimensional finite element model of malunion calcanens during gait

Objective: To analyze the stress distribution of calcaneus with posterior articular facet compressed after fracture and talus during gait. Methods: A wedge under the posterior articular was transected from a normal finite element model of calcaneus and talus to simulate malformation of compression of the posterior facet after fracture of calcaneus. The model was used to simulate for three subphases of the stance during the gait( heel-strike, midstance, push-off) and calculate the finite element.The results were compared with normal situation. Results: The stress distribution within the bone in situation of malformation was obtained and regions of elevated stresses for three subphases were located. The results were significantly different from that of normal situation. Conclusion: The simulation of calcaneus and talus in malformation has important clinic implication and can provide an insight into the factors contributing to many clinic pathogenic changes after fracture of calcaneus.     

Comparative study of various internal fixation methods for treating patellar fractures by three-dimensional photoelasticity

Objective: To compare the biomechanical basis of 3 different internal fixation methods: nitinol patellar concentrator (NT-PC),tension band and wire circle in treating patellar fractures. Methods:The epoxy resin three dimensional photoelasticity patellar models were made by precise moulding, and were fixated by nitinol patellar concentrator (NT-PC) , tension band and wire circle respectively. The patellar models with frozen stress stripes were put into the polarized light field and the stress distributions were compared. As for the model fixated by NT-PC, by dividing layer, photographing and tracing, we used the iterative method to calculate the stress value of every internal node of the epoxy resin patellar model, and the character of stress was analyzed. Results:An overall stress field was yielded when the patellar model was fixated by NT-PC, and the stripes were more than that of tension band model and wire circle model, which have only few stress stripes in the fixated layers. Further analysis indicated that there were continuous fixated stresses in the facies articularis and distal pole of patella, and the character of stresses produced by NT-PC were mainly in longitudinal direction, then in transverse direction. The shearing stresses were small. Conclusion: The initiative and continuous memorial stress of NT-PC and its overall stress distribution character are the essence of NT-PC distinguished with tension band and wire circle in treating patellar fractures. The stress character produced by NT-PC is good for the stability of fracture site and prompts fracture healing.     

The finite element analysis of cemented long and short stem prosthetic replacement in aged patients with comminuted intertrochanteric fracture

<正>Objective To investigate the stress distribution of the femur after cemented prosthetic replacement in aged patients with comminuted intertrochanteric fracture and to analyze the difference of stress distribution between cemented long and     

Three dimensional finite element analysis of acetabulum loaded by static stress and its biomechanical significance

Objective：To explore the mechanical behavior of acetabulum loaded by static stress and provide the mechanical basis for clinical analysis and judgement on acetabular mechanical distribution and effect of static stress. Methods：By means of computer simulation, acetabular three dimensional model was input into three dimensional finite element analysis software ANSYS7.0. The acetabular mechanical behavior was calculated and the main stress value, stress distribution and acetabular unit displacement in the direction of main stress were analyzed when anterior wall of acetabulum and acetabular crest were loaded by 1 000 N static stress. Results ：When acetabular anterior wall loaded by X direction and Z direction composition force, the stress passed along 4 directions： （1）from acetabular anterior wall to pubic symphysis along superior branch of pubis firstly, （2）from acetabular anterior wall to cacroiliac joint along pelvic ring, （3）in the acetabulum, （4）from the suffered point to ischium. When acetabular crest loaded by X direction and Y direction composition force, the stress transmitted to 4 directions： （1）from acetabular crest to ilium firstly, （2）from suffered point to cacroiliac joint along pelvic ring, （3） in the acetabulum , （4）along the pubic branch, but no stress transmitted to the ischium branch. Conclusion：Analyzing the stress distribution of acetabulum and units displacement when static stress loaded can provide internal fixation point for acetabular fracture treatment and help understand the stress distribution of acetabulum.     

Fracture resistance and pattern of the upper premolars with obturated canals and restored endodontic occlusal access cavities

We studied whether obturing canals and restoring endodontic occlusal access cavities on upper premolars could provide acceptable resistance and pattern to fracture.Eighteen upper premolars were divided equally into 3 groups.Group 1 consisted of intact controls;group 2 had access cavities and root canal preparations;group 3 as in group 2 but obturated with gutta-percha and AH26,and the access cavity restored with glass ionomer and composite.Specimens were submitted to compressive strength testing using the Hounsfield Universal H50KM testing machine with a load cell of 2000 Newtons and a crosshead speed set at 1.0 mm/min until fracture.The results from the compressive strength tests showed that intact controls （1105.83±90.93 MPa） and restored premolars （936.67±44.67 MPa） were significantly different from premolars with unrestored access cavities 568.33±105.49 MPa.There was no significant difference between intact controls and restored premolars.The predominant fracture pattern for intact teeth was an oblique fracture.For premolars that had endodontic access cavities,restored or unrestored,the most common fracture pattern was a vertical fracture.The restoration of occlusal access cavities with glass ionomer and composite provided fracture resistance close to that of intact controls,but when restored teeth fractured,they were predominantly non-restorable.     

Comparisons in finite element analysis of minimally invasive,locking,and non-locking plates systems used in treating calcaneal fractures of Sanders type Ⅱ and type Ⅲ

Background Calcaneal fractures are relatively common but complex,while the treatment of these fractures is still controversial.The objective of this study was to compare the biomechanical stability of minimally invasive,locking,and non-locking plating systems used for fixing Sanders type Ⅱ and type Ⅲ calcaneal fractures.Finite element analysis was used for comparing the three types of plating systems.This study helped in guiding the clinical management of calcaneal fractures.Methods The CT data acquired from a volunteer was used to construct a finite element model of calcaneus.The fracture lines were made according to Sanders type Ⅱ （A,B,C） and type Ⅲ （AB,AC,BC） and six calcaneal fractures models were constructed accordingly.Three fixation methods used in clinical treatment were simulated by design tools （minimally invasive plating with percutaneous screws,Y-size non-locking plating,and locking plating） and then fixed to these fracture models with the help of clinical principles.The single minimally invasive plating fixation was also tested to compare the function of percutaneous screws.Then,the neutral force was applied on established methods.The displacement and presses distribution condition in various plating models were analyzed and compared.Results The levels of displacement and compressive press on the bone around fixation or strains on plating were within the physiological limit,indicating that the three methods were suitable for application.Compared with the locked and unlocked plates,the minimally invasive plating caused a relatively lower displacement without the high stress in bone or fixation.The minimum stress in fixation was observed in locking plate as the distribution of stress was concentrated in the anterior part of locking plate.Conclusions The minimally invasive plating method could be a better alternative method in treating Sanders type Ⅱ and type Ⅲ calcaneal fractures.The observed stiffness of locking plate was not obviously stronger than unlocked plate.     

Biomechanical comparison of gourd-shaped LCP versus LCP for fixation of comminuted tibial shaft fracture

The purpose of this study was to compare monotonic biomechanical properties of gourd-shaped LCP fixation with LCP fixation of human tibial shaft in gap fracture mode. Twenty paired fresh cadaveric human tibias were randomly divided into 4 groups (5 pairs each): (1) axial loading single cycle to failure testing, (2) torsion single cycle to failure testing, (3) 4-point bending single cycle to failure testing, and (4) dynamic 4-point bending testing. A 7-hole 4.5 mm gourd-shaped LCP was secured on the anteromedial surface of 1 randomly selected bone from each pair, respectively, using 6 locking screws in the 1st, 2nd, 3rd, 5th, 6th and 7th hole with the middle hole unfilled and just located at the mid-diaphysis of the tibia. A 7-hole 4.5 mm LCP was secured on the other bone with the same method. Standard AO/ASIF techniques were used. After fixation finished, a 10 mm gap in the mid-diaphysis of tibia was created, centrally located at the unfilled hole. The axial, torsional, and bending stiffness and failure strengths were calculated from the collected data in static testings and statistically compared using paired Student’s t-test. The 4-point bending fatigue lives of the two constructs were calculated from the dynamic testing data and also statistically compared using paired Student’s t-test. Failure modes were recorded and visually analyzed. P<0.05 was considered significant. Results showed that the axial, torsional and bending stiffness of gourd-shaped LCP construct was greater (4%, 19%, 12%, respectively, P<0.05) than that of the LCP construct, and the axial, torsional and bending failure strengths of gourd-shaped LCP construct were stronger (10%, 46%, 29%, respectively, P<0.05) than those of the LCP construct. Both constructs failed as a result of plate plastic torsional deformation. After axial loading and 4-point bending testings, LCP failed in term of an obvious deformation of bent apex just at the unfilled plate hole, while the gourd-shaped LCP failed in term of a deformation of bent arc between the 3rd and 5th holes, which indicated a more consistent stress distribution on gourd-shaped LCP. Fatigue life of gourd-shaped LCP construct was significantly greater than LCP construct (153 836±2 228 vs. 132 471±6 460 cycles, P<0.01). All constructs failed as a result of fracture of the plate through the compression hole of the unfilled combination screw hole. The biomechanical testing showed that gourd-shaped LCP can provide greater stiffness and strength, and longer fatigue life than LCP. The gourd-shaped LCP may be more advantageous mechanically and may reduce the plate breakage rate clinically.     

Duck hepatitis B virus infection and duck hepatocellular carcinoma.

To study the relationship between duck hepatitis B virus (DHBV) infection and duck hepatocellular carcinoma (DHCC), histological examination and DHBV DNA hybridization were performed in 875 ducks from three flocks in Qidong County. Among them, 34 suffered from hepatoma, including 23 hepatocellular carcinoma, 8 cholangiocarcinoma and 3 hepatocellular-cholangiocarcinoma. Of the 34 ducks with hepatoma 27 were positive for DHBV DNA in the liver and/or serum. DHBV DNA was demonstrated in neoplastic nodules of 22 ducks. Southern blot analysis showed that 13 cases were of the integrated pattern of DHBV DNA in neoplastic nodules. The paratumor tissues of 14 ducks with massive tumor were analysed at the same time. Five cases showed integrated pattern, 4 cases free pattern and the other 4 cases both integration and free pattern of DHBV DNA. The hybridization pattern of DHBV DNA in tumor nodule was different from that in paratumor regions in 11 cases and identical in 3 cases. DHBV antigen was positive in 13 tumor nodules and 21 paratumor tissues in the 34 ducks with hepatic tumor by both victoria blue and orcein stain methods. Advanced liver diseases were found in 30 out of the 34 ducks with hepatoma, including 12 cirrhosis and 18 chronic active hepatitis. In southern blot analysis of 122 DHBV DNA positive Qidong ducks without hepatoma, only free pattern of DHBV was seen, while 44 control ducks from Changchun were negative for DHBV DNA. Neither hepatic tumor nor liver diseases were seen in the control ducks. The results suggest that hepatocellular carcinoma in ducks is similar to that in human HCC. They have a high frequency of viral DNA integrated into the host genome and a liver disease background.

     

肘关节有限元模型模拟碰撞损伤的生物力学特性分析

目的 利用有限元法建立肘关节的三维有限元模型,动态模拟肘关节以不同角度撞击地面,分析肘关节的生物力学特性.方法 选取1名健康青年男性志愿者,肘关节屈曲90°行CT扫描,应用Mimics、Geomagic、UG、Hypermesh等软件对所得数据进行三维重建,建立肘关节的三维有限元模型;在Abaqus软件中模拟肘关节以不同角度(前臂与地面呈30°、60°、90°)撞击地面时,计算骨皮质破裂的临界速度及显著破裂时的速度,分析应力传导及其大小、分布等的变化规律.结果 肘关节屈曲90°状态发生正面碰撞时应力传导主要集中在肱骨髁、肱骨滑车及尺骨鹰嘴等部位,而桡骨头应力传导较小;当肘关节与地面撞击(前臂与地面分别呈30°、60°、90°)时,骨皮质破裂临界速度分别为11.4、9.3、13.8 m/s;前臂与地面分别呈30°、60°撞击,撞击速度分别达15.0、13.0 m/s时,尺骨鹰嘴呈粉碎性骨折;前臂与地面呈90°撞击,撞击速度达18.0 m/s时,肱骨远端呈明显横行骨折.结论 应用有限元建模分析软件构建的人体肘关节有限元模型可用于外力作用下肘关节损伤机制的研究,也可用于肘关节损伤时暴力的大小、速度、方向的推断.     

儿童肱骨远端有限元模型的建立及力学分析

目的建立儿童肱骨远端有限元模型,并模拟肱骨轴向受力状态下应力分布,为肱骨的生物力学研究提供数值分析模型。方法通过CT扫描正常儿童右侧肱骨,获得连续断层图片,导入mimics13.1医学建模软件进行网格划分、材料属性赋值,生成有限元模型,应用有限元分析软件ANSYS10.0,约束边界条件,模拟肱骨轴向受力状态进行加载,得出肱骨远端有限元模型上的应力分布。结果建立的肱骨远端有限元模型节点共50364个、四面体单元29951个。肱骨在轴向载荷状态下应力集中主要位于髁上区,且尺侧应力集中现象较桡侧明显。结论应力分析结果解释了肱骨骨折好发于髁上区的原因,髁上区尺侧骨质的高应力是肱骨髁上骨折致肘内翻的基本生物力学因素。     

天鹅型记忆接骨器治疗肱骨骨折和骨不连的三维有限元分析

目的：研究天鹅型记忆接骨器（SMC）治疗骨折和骨不连及其产生的动态记忆应力促进骨愈合的生物学基础。方法：利用计算机仿真三维有限元技术,对SMC固定肱骨的生物力学行为进行模拟,接骨器有限元模型共划分了3487个单元,节点数为5397,单元采用20节点四面体三维砖块单元;肱骨有限元模型共划分5783个单元,节点数9863,单元采用10节点四面体三维单元,结果：接骨器固定肱骨后其内表面受拉力,外表面受压力,变形最大的加压部第一结构主应力最大值分别为224．5MPa和－34MPa,远小于其极限应力与疲劳极;其维持轴向的动态记忆持骨力为125．05N,纵向动态记忆加压力196N,被固定肱骨应力分布均匀,各节点所受应力主要为正应力。结论：SMC有良好的耐疲劳与重复使用性,其固定后产的动态记忆加压应力场,有利于固定肱骨的稳定并促进骨愈合。     

超关节外固定架有限内固定治疗肱骨远端粉碎骨折疗效观察

目的探讨治疗肱骨远端粉碎性骨折的手术及疗效。方法自2009年2月至2011年8月对22例肱骨远端粉碎性骨折患者进行绞链式超关节外固定支架结合有限内固定治疗。其中男16例,女6例;年龄26～55岁,平均36岁。根据AO分型,C1型2例,C2型10例,C3型10例。结果所有病例均随访6个月,平均骨折愈合时间为2.8个月,前臂旋转活动度超过100°,肘关节屈伸活动度超过90°,且无神经损伤及术后感染。根据改良Glssebaum评分系统评定疗效,治疗的总优良率为81.8%。结论使用绞链式超关节外固定支架结合有限内固定治疗肱骨远端粉碎性骨折疗效较好,值得临床推广。     

锁骨三维有限元模型的建立及生物力学分析

目的:建立正常锁骨有限元模型,并模拟锁骨轴向受力状态下应力分布及应变特征,为锁骨的生物力学研究提供数值分析模型.方法:通过CT扫面正常成年男性右侧锁骨,获得连续断层图片,导入Simpleware医学建模软件生成实体模型后,应用通用有限元分析软件ANSYS 10.0,进行网格划分、材料属性赋值生成有限元模型.约束边界条件,模拟锁骨轴向受力状态进行加载,得出锁骨有限元模型上的应力分布与应变结果.结果:建立的锁骨有限元模型节点共62 182个、四面体单元40 878个.锁骨在轴向载荷状态下应力集中主要位干锁骨干中1/3区域,且下表面应力集中现象较上表面明显.结论:应力分析结果解释了锁骨骨折好发于中1/3的原因,并且发现主要应力集中于下表面,锁骨产生断裂的弯矩位于冠状面,提示临床内固定治疗锁骨中段骨折时,钢板放置于上表面能有效抵抗产生的弯矩,避免内固定失败.有限元分析法可较好分析锁骨的生物力学特点.     

肱骨外侧髁骨折的伸肌腱作用机制探讨

目的 采用光学弹性实验及三维有限元计算分析法，研究伸肌腱在不同体位加载下对肱骨外侧髁的应力作用规律，探讨肱骨外侧踝骨折的发生机制及治疗方案。方法 分别制造儿童肱骨三维光学弹性及有限元模型，模拟伸屈肘及前臂旋前、中立、旋后和内外翻等多种体位加载，观察和计算分析相应部位的应力分布状况。结果 各种体位肱骨外侧髁区平均应力值均最大；半屈肘时应力值远大于相应伸肘时，而伸肘时的伸肌腱作用节点应力值却大于外侧髁区；伸肘内翻位有伸肌腱作用力的加载下，肱骨外髁上部为拉应力条纹，内髁上部为压应力条纹。结论 儿童半屈肘位时易发生肱骨外侧髁骨折，而在伸肘内翻位时，以伸肌腱牵拉为主的弯力偶矩可拉脱外侧髁形成骨折；肱骨外侧髁骨折的复位可利用伸肌腱的牵拉作用，而固定则尽量避免伸肌腱的牵拉。     

肱骨髁上部的二维光弹性实验研究

采用二维光弹生实验研究肱骨髁上部的力学性能。结果显示：旋后位使髁上内侧产生压应力，髁上外侧产生拉应力；中立位和旋前位使髁上内侧产生拉应力，髁上外侧产生压应力。表明实验与临床相符，为临床合理固定肱骨髁上骨折提供了理论依据。     

天鹅型记忆接骨器治疗肱骨骨折和骨不连的生物力学研究

目的：研究天鹅型记忆接骨器（SMC）治疗骨折骨不连的生物力学特征。方法：利用电测、二维（2D）、三维（3D）光弹性技术,通过贴片,标定电测得到SMC的载荷－应变曲线,并通过固定新鲜人体肱骨,计算SMC的动态记忆持骨力值;通过2D光弹性技术计算SMC鹅颈加压部动态记忆加压力值,用精密浇铸法得到肱骨环氧树脂3D光弹性模型,模仿临床使用,得到SMC固定下的肱骨模型3D应力场分布,同时利用Leize偏光显微镜结合三维光弹法,计算肱骨模型考察点3D应力场中的6个应力分量。结果：电测SMC动态记忆持骨的生物学力值为110．35N。2D光弹测得纵向动态记忆加压力为163．88N。3D光弹测得SMC的鹅颈－加压部、鹅体－接骨板部、鹅翼－持骨部三部相互协调,记忆持骨,形成动态3D立体固定,产生全场应力分布。3D应力分离表明SMC固定后骨折端的应力基本为正应力。结论：SMC空间立体记忆固定的应力场,有利于骨折、骨不连的治疗、允许早期功能锻炼并促进骨愈合。     

肱骨近端骨折合并肩袖损伤的年龄分布和Neer分型分析

目的 肱骨近端骨折易造成不同程度的肩袖损伤。严重的肩袖损伤是肱骨近端骨折术后肩关节活动受限的常见原因。本文旨在探讨肱骨近端骨折合并肩袖损伤与骨折Neer分型和年龄分布的相关性。 方法 采用自行设计的调查问卷，回顾性分析海口市某三甲医院2012年1月—2016年12月126例肱骨近端骨折行手术治疗患者的临床资料。比较不同肱骨近端骨折Neer分型、不同年龄分层肱骨近端骨折合并肩袖损伤的发生率。 结果 不同性别肱骨近端骨折病人年龄、骨折类型的差异无统计学意义(χ2=0.030,P=0.985)。126例肱骨近端骨折病人中，49例(38.9%，49/126)术中确认存在肩袖损伤，其中41例在术前通过MRI得到确认。合并肩袖损伤的肱骨近端骨折病人的平均年龄为(76.9±9.8)岁，与不合并肩袖损伤的病人的平均年龄(53.4±8.3)岁比较，差异有统计学意义(t=3.178,P=0.034)。肱骨近端骨折Neer分型三部分骨折合并肩袖损伤的发生率最高，为49.3%(37/67)。 结论 肱骨近端骨折合并肩袖损伤病人的比例随着年龄的增加而增加；肱骨近端骨折Neer分型三部分骨折常常合并肩袖损伤，这对临床肱骨近端骨折的处理有指导意义。