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【讨论】请教骨折固定的问题,万分火急,在线等候

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发表于 2003-4-30 11:36:27 | 显示全部楼层 |阅读模式 来自 西安交通大学
现在导师要我分析股骨颈骨折的问题,就是股骨颈骨折后用螺钉紧固,在坐手术时拧紧螺钉,所以在断面有预紧力,然后分析在股骨受力时的情况,骨的皮质骨(分左右两个断面)是从proe中建好分别导入的,
然后在ansys中用皮质骨内腔的面生成松质骨,这样保证他们共面
然后建钉子的模型,钉子和相邻的骨头用glue命令粘结起来,保证受力时钉子和骨骼一起变形,不分离。骨骼断面如何定义呀
因为松质骨和密质骨的材料不同,我要得出的结果是看看断面见的压应力和剪力
 楼主| 发表于 2003-4-30 15:14:35 | 显示全部楼层 来自 西安交通大学

回复: 【讨论】请教骨折固定的问题,万分火急,在线等候

Simdroid开发平台
怎么大家没人回呀
发表于 2003-5-1 10:43:42 | 显示全部楼层 来自 美国

回复: 【讨论】请教骨折固定的问题,万分火急,在线等候

既然材料性质不同,可以通过定义两种材料来实行吗
  
没看懂你的问题
 楼主| 发表于 2003-5-1 10:49:05 | 显示全部楼层 来自 西安交通大学

回复: 【讨论】请教骨折固定的问题,万分火急,在线等候

定义接触时定义两个接触对
 楼主| 发表于 2003-5-1 14:50:04 | 显示全部楼层 来自 西安交通大学

回复: 【讨论】请教骨折固定的问题,万分火急,在线等候

三楼的大侠
不知那里不明白
发表于 2003-5-1 17:04:38 | 显示全部楼层 来自 北京

回复: 【讨论】请教骨折固定的问题,万分火急,在线等候

你用实体元建立模型,不存在骨断面的问题。
预紧力用PRETS179单元,很简单。
还可以用降温法或接触初始正间隙法,用CNOF值来调整。
 楼主| 发表于 2003-5-3 15:48:29 | 显示全部楼层 来自 西安交通大学

回复: 【讨论】请教骨折固定的问题,万分火急,在线等候

谢谢斑竹
发表于 2004-7-4 23:47:54 | 显示全部楼层 来自 Reserved

回复: 【讨论】请教骨折固定的问题,万分火急,在线等候

http://www.algor.com.cn/
University of Georgia Study Uses FEA to Examine the Healing of Animal Bones
  
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This photo shows a dog with an ESF on the left, front leg. This device stabilizes the bone while it heals and allows the dog to maintain the use of its limb.  
  
   
   
     
These X-ray images show fractured dog legs being stabilized by different ESF configurations.  
  
   
   
     
Dr. Aron抯 research included laboratory testing on cadaver dog bones to study the bone/pin interference. The inset shows an IM pin within a dog bone. The irregularity of the medullary canal and the thinness of the cortex make an ESF necessary.  
  
   
   
     
A linear static stress analysis was performed on a model that represents a fractured dog bone, IM pin and KE ESF. Von Mises stresses at the bone/pin interface are especially important.  
  
   
   
     
Aric Applewhite, DVM, helped to develop the finite element model of the dog bone with an IM pin and ESF.  
  
   
   
According to the 2003/2004 National Pet Owners Survey conducted by the American Pet Products Manufacturing Association, 65 million dogs and 77.7 million cats are found in at least one-out-of-three U.S. households. When pets break a bone in an accident, such as being hit by a car, veterinarians often mend the fracture with a combination of stabilization devices called intra-medullary (IM) pins and external skeletal fixators (ESFs), a technique that is employed daily across the United States. Research conducted at the University of Georgia under the direction of Dennis Aron, Doctor of Veterinary Medicine (DVM), using ALGOR finite element analysis (FEA) software is helping to establish better guidelines for how these stabilization devices can best be used to promote healing of animal fractures.  
  
Stabilization Devices Help Fractures Heal
Physical trauma often results in the fracture of one or more of the long bones of the limbs. This type of bone consists of a dense cortex layer with a central cavity termed the medullary canal, which contains softer tissue. One technique for mending a fractured bone involves inserting an IM pin into the bone. When this technique is used on humans, the medullary canal is first hollowed out, or reamed, to achieve a perfectly cylindrical shape matching the diameter of the IM nail, as it is called when used on humans. The inserted nail achieves a tight press-fit within the bone, preventing bending, rotation and translation.  
  
Dog and cat bones cannot be reamed, however, because the cortex of their bones is not as thick as human bones. Reaming is also made more difficult in dogs and cats because the long bones tend to not be as straight as human bones. This is not just a matter of pets being smaller; but rather is a species variation. While IM pins can effectively prevent bending when used on dogs and cats, they frequently are not effective as the only method of stabilizing a fracture because the pins do not achieve a tight fit within the bone.  
  
Veterinarians, therefore, often combine the use of IM pins with ESFs. An ESF consists of a number of pins that penetrate the bone and exit through the skin to attach to rigid bars on the outside of the body. This device stabilizes the bone as it is healing while still allowing the animal to maintain the use of its limb.  
  
Several different brands of ESFs are used in veterinary medicine, such as Kirschner-Ehmer (KE) and the IMEX SK?(SK). The variation in the brands of ESF devices involves different types of clamps that affix the pins to the bar, different types of pins that engage the bone and different material(s) that comprise the components (i.e., connecting bar and clamps). Additionally, veterinarians must select the number, type and configuration of ESF pins to provide adequate stabilization of the fracture.  
  
Current guidelines for ESFs are based on small clinical studies that have looked at the effectiveness of different ESFs, both with and without an IM pin in various fracture scenarios. 揢sing software technology, such as finite element analysis, allows us to look at a greater number of ESF variations than is practical with clinical or laboratory testing,?said one of Aron抯 team members, Aric Applewhite, DVM. 揟he project underway at the University of Georgia will help us to compare different types of ESF devices, a variable number of ESF pins and the added stability provided by an IM pin in different fracture scenarios. Our goal is to determine if IM pins are necessary and which ESF configurations are best at stabilizing a fracture.?h4> Modeling a Fractured Bone  
  
揂s non-engineers, we needed an FEA package that was easy to use and understand,?said Applewhite. 揥e chose ALGOR because of its reputation for being user-friendly and providing quality technical support. ALGOR抯 technical support staff was always available. They provided us with invaluable assistance throughout our project.?p> The finite element model created in ALGOR抯 Superdraw III consists of solid and beam elements. Solid brick elements comprise the IM pin, two pieces of bone and sections of the spongy material of the medullary canal, while the ESF frame is represented by beam elements.  
  
揗odeling the IM pin in the medullary canal was the most challenging part of the whole modeling process,?said Applewhite抯 teammate, Heidi Radke, DVM. 揟hrough trial and error, we learned that actually modeling sections of the spongy material of the medullary canal provided more accurate results than approximating this region with contact elements.?p> The bone geometry was simplified to a hollow cylinder, the diameter of which was based on measurements of a large-sized (about 30 kg or 66 lbs) dog. The geometry was simplified to remove the variables of differences in breeds and different sizes of animals and, therefore, enabled the researchers to concentrate on the ESF and how it behaves in relation to an idealized bone/IM pin structure.  
  
Published material properties for bovine bones, which are similar in strength to dog bones, were applied to the bone parts in the model. The properties of 316L stainless steel were used for the pins. Stainless steel was used to model the KE ESF and a carbon fiber composite was used for the SK ESF.  
  
A force was applied at the femoral head to represent the weight of the dog. The model was fully constrained at the bottom of the bone and stabilizing elastic constraints were added to maintain spatial alignment while the model displaced vertically. Linear static stress analyses were performed on all of the models in the study.  
  
In reviewing the analysis results, von Mises stresses at the bone/pin interface and deflections at the gap between the pin and bone were especially important. The first study that compares KE and SK unilateral ESFs with IM pins has been completed. The results were validated with mathematical methods, including convergence and patch testing, and against data from laboratory testing. The results of this first study were presented in January 2003 at the Annual Meeting of Bioengineering in Athens, Georgia. Comparing other variations in the IM pin/ESF configuration is an ongoing project that will provide veterinarians with improved solutions for treating pet fractures in the future.  
  
Veterinary surgeon Dennis Aron oversees this research at the University of Georgia, where he is a professor. Veterinarians Aric Applewhite and Heidi Radke developed the finite element models for this project, assisted by engineers Mark Evans, Ph.D. and Guigen Zang, Ph.D.

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发表于 2004-7-4 23:50:26 | 显示全部楼层 来自 Reserved

回复: 【讨论】请教骨折固定的问题,万分火急,在线等候

当宠物在事故——例如车祸——中发生骨折时,兽医通常会使用称为intra-medullary(IM)的加固针和外部的骨骼固定装置的组合来治疗骨折,这项技术目前在全美国范围内得到了广泛使用。由University of Georgia的兽医药学博士Dennis Aron主导的研究使用了ALGOR的有限元分析软件,该项研究有助于在动物骨折治疗方面指导对这些装置的最佳使用方法。

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发表于 2005-6-1 00:08:50 | 显示全部楼层 来自 韩国

Re:【讨论】请教骨折固定的问题,万分火急,在线等候

股骨颈骨折所用的是Compression Hip Screw System!
这方面的FEA多得很!
“预紧力”发生在断裂面=你可以使用一定摩擦系数的Contact pair(ansys中)
“glue命令粘结起来”=ansys 中可以把两种不同材料粘起来“glue”,分析是可以作为一个实体分析的
jumpman 该用户已被删除
发表于 2005-9-6 13:39:59 | 显示全部楼层 来自 台湾
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