移植隧道对股骨力学性能的影响

该文应用Mimics 8.1软件由膝关节螺旋CT数据重构3D股骨模型。基于该模型依据单束、双束韧带重建手术的要求,建立了膝关节正常股骨、含单移植、双移植隧道股骨的三种近似三维有限元模型。根据股骨在关节屈伸中承受载荷的性质提取压缩、弯曲和扭转三种作用力,分别加载到上述三种有限元股骨模型上,进行有限元仿真。该文提出截面应力比较法,从股骨截面应力云图中提取最大有效应力值与最大第一主应力值为指标来评定隧道对股骨承载性能的影响,通过对比分析表明:无论采用前交叉韧带重建的哪种方法,在正常压缩、弯曲和扭转的三种负载下,隧道对ACL重建后的截面应力分布状态影响不明显,对股骨最大有效应力值的影响较弱(应力变化量≤5.06%),对股骨第一主应力值的影响也较小(变化量≤6.85%)。总之,ACL重建移植隧道对股骨承载应力的影响较小。在临床手术中医生对股骨隧道的视点只需放在起止点的准确选取上。该文提出的截面应力比较法丰富了ACL重建术后的股骨力学性能评定的技术与方法。     

ACL单束／双束重建对胫股关节应力分布影响

该文基于正常膝关节的MRI图像数据,构建正常／单束／双束韧带重建胫股关节整体模型,通过对这3个关节整体模型分别加载单一负荷（轴向力）及组合负荷（轴向力和扭矩）进行有限元仿真,得到3个整体模型在两类负荷作用下的应力分布;通过从整体模型的应力云图中提取股骨、胫骨、关节软骨、半月板及后交叉／内侧／外侧韧带的表面应力等进行对比...     

前交叉韧带单束移植隧道对胫/股骨承载影响的正交实验

利用膝关节处的密质骨和松质骨在CT成像中灰度值不同的特点,通过选取合适的阈值建立了含密质骨和松质骨的股骨和胫骨三维模型。同时,在视觉导航确定前交叉韧带(ACL)单束移植隧道起止点位置的条件下,按正交实验变换ACL移植隧道参数(孔径D、冠/矢状面上的倾角α/β),构建了含隧道股骨/胫骨模型。正交实验分为5个水平,依据在直立位胫/股骨处于静平衡时以等力传递载荷的原则,分别对含隧道的股骨及胫骨施加等值压缩和弯曲载荷进行有限元分析,得到隧道参数对股骨和胫骨应力影响特性。正交实验表明,三个参数对含隧道股骨的应力影响不明显(应力增量≤7.93%),但对含隧道的胫骨应力影响显著:受压缩载荷时冠/矢状面倾角α/β产生的应力增量分别达到39.10%和36.88%,而受弯曲载荷时矢状面倾角β引起应力增量最大可达24.66%。     

磁共振成像在诊断前交叉韧带损伤中的应用研究

目的:对磁共振成像在诊断前交叉韧带损伤中的应用效果研究。方法:按照本次研究排纳标准选取2015年1月-2016年1月于我院进行诊断治疗的交叉韧带损伤患者共80例,先对患者使用磁共振成像检测,再用关节镜进行诊断,统计比较并分析两种方法的诊断结果。结果:磁共振诊断结果为:完全断裂16例,部分断裂为24例,胫骨端撕脱14例,ACL正常36例;关节镜诊断结果为:完全断裂15例,部分断裂为27例,胫骨端撕脱12例,ACL正常36例,两种方法的诊断结果无显著差异(P0.05)。结论:磁共振成像作为一种无创的检测方法可以被用于交叉韧带损伤的临床诊断。     

半月板移植的固定法对胫股关节屈曲中韧带及骨骼的力学特性影响

基于正常膝关节4个屈曲角度(0°/25°/60°/80°)下的MRI图像数据,构建了正常以及内侧半月板移植术中双隧道固定和三隧道固定的胫股关节有限元模型,对屈曲角系列下的4种模型分别施加10N?m的内外旋扭矩进行有限元仿真,得到各模型在两种载荷作用下的应力及位移分布,通过从仿真结果中提取各韧带表面的最大拉应力、韧带内的张力及韧带的最大变形量以及股骨、胫骨最大等效应力进行对比分析,获得了内侧半月板移植的双隧道/三隧道固定方法对胫股关节屈曲中韧带及骨骼力学特性的影响。结果表明:同类异体半月板移植的两种固定方法均在一定程度上改善了半月板切除引起的韧带力学行为的异常情况,尤其以采用三隧道固定后的改善更为明显。与双隧道固定相比,三隧道固定使各屈曲角度下韧带表面最大拉应力的变化更为小些,且对各韧带内张力的大小的改变也更微小;虽然三隧道固定使两种载荷作用下韧带的平均变形量的变化更大一些,但4个屈曲角度下的平均变化百分比不超过10%。同类异体半月板移植的两种固定方法均在一定程度上影响股骨和胫骨应力分布,但采用三隧道固定后的影响相对于双隧道固定的小。综合而言,三隧道固定比双隧道固定更利于移植膝韧带力学性能的恢复和胫骨/股骨接近正常的骨骼应力分布。该文的研究结果能为同类异体半月板移植手术的临床实施和术后分析提供参考数据。     

一种基于SPIHT和匹配追踪的图像编码方法——SPMP算法

为了更好地利用图像的结构特征,提高图像重建的质量,提出了一种基于多级树集合划分(SPIHT)和匹配追踪(MP)的分层图像编码方法--(SPMP)算法.该方法首先采用拉普拉斯金字塔(Laplacian Pyramid)算法将原始图像分解成低频平滑层和高频细节层,然后使用离散小波变换和SPIHT算法编码图像的低频成分,使用...     

基于监督式等距映射的人脸和表情识别

提出了一种基于监督式等距映射的人脸和表情识别方法,该方法能同时完成身份和表情的识别.首先,运用监督式等距映射,将训练集中的人脸表情图像投影到低维流形空间,在这个流形空间里,图像的投影不仅实现了按其身份的分离,同时在同身份图像的内部,又实现了按其表情的聚类.然后,用非线性投影,将待测图像嵌入到流形空间.最后,采用加权knn分类器,识别出它的身份和表情.在Coln-Kanade和JAFFE人脸库上的实验表明,该方法对人脸和表情的识别的准确率比较高.     

CCD高分辨成像的梯度解析法

基于序列图像重建的高分辨成像技术需要获取互有位移的序列图像,并需利用图像重建算法进行高分辨率图像重建。为此,设计了一种利用压电陶瓷体控制CCD位移来获取互有微小位移的序列图像的装置,在此基础上提出了一种基于梯度理论从序列图像重建高分辨率图像的算法——梯度解析法。该解析法根据图像灰度场梯度理论,同时考虑了图像的更高频成分,提高了重建图像分辨率。仿真实验显示,该算法与已有算法相比,重建图像的失真度降低40％以上。     

基于欧拉角变换的脑外科机器人系统手术规划方法

在分析脑外科定向手术机器人系统对手术刀进刀路径要求的基础上,研究了二维和三维手术规划,提出了基于欧拉角变换的脑外科机器人定向手术的规划办法;在详细分析手术进刀路径的确定方法后,给出了基于DICOM医疗图像的脑外科机器人系统手术规划的具体实现过程.该规划方法避免了手术路径确定过程的盲目随机性,可使医生高效、快速、准确地确定手术进刀路径.     

一种基于模型的光学层析图像重建方法

光学层析图像重建是个病态问题,测量误差会在重建过程中被放大,对此,提出一种以广义高斯马尔可夫随机场模型为先验信息的光学层析图像重建方法.重建过程是对目标函数的优化过程,目标函数关于光学参数的梯度计算是算法中的难点,因此,提出一种基于梯度树的梯度计算方法.文中分别给出了吸收系数和散射系数的重建结果,并引入三个指标因子衡量重建图像的质量,进而列出不同重建算法下,重建图像的指标值.最后通过对重建结果和指标因子取值的比较,分析基于模型的重建算法的有效性.     

Development of a silk and collagen fiber scaffold for anterior cruciate ligament reconstruction

The objective of this study was to determine a silk-collagen fiber ratio for an anterior cruciate ligament (ACL) reconstruction composite scaffold device. Composite fiber scaffolds with silk volumes ≥14 % and collagen volume <86 % demonstrated comparable or greater initial ultimate tensile stress relative to the human ACL. Silk scaffolds implanted subcutaneously and intraarticularly in rabbits demonstrated an 84 and 92 % reduction in strength with a 26 and 22 % reduction in volume after 8 weeks, respectively. The mechanical degradation findings of this preliminary study suggest that a composite scaffold with an initial UTS value of at least 129 MPa, or roughly a 48:52 silk to collagen volume ratio meets the minimal mechanical requirements necessary to proceed to a functional ACL reconstruction study in vivo.     

Studies of polyurethane urea bands for ACL reconstruction

The present report describes the mechanical tests, in vitro and in vivo studies of a poly(urethane urea) (PUUR) intended for clinical use in anterior cruciate ligament (ACL) reconstruction. In the mechanical tests, no evidence of severe fatigue was observed after repeated cyclic loading. Testings for mutagenicity and delayed contact hypersensitivity were found negative. Three in vivo studies were performed in rabbits and minipigs. Altogether 35 rabbits were operated upon in (1) an intraarticular implantation study, performed to evaluate the soft tissue response to woven bands and fiber bundles of PUUR and (2) a rabbit ACL study, examining the function of the PUUR ACL replacement and the tissue response to the material. In a third study, PUUR ACL replacement in minipigs was evaluated. Taken together, ingrowth of connective tissue in close contact with the PUUR fibers was detected both in rabbits and minipigs. The first clear histological signs of degradation of the polymer was detected after 24 months. In conclusion, the evaluated mechanical properties of the PUUR band correspond to those of the mature, human ACL. Furthermore, both from a histological and functional point of view, the PUUR woven band show interesting properties for future clinical ACL reconstructions.     

ACL移植物初始力对胫股关节接触性能影响

为深入研究ACL重建中移植物初始力对术后膝关节性能的影响,该文从MRI数据中提取膝关节各组织来构造出正常膝关节三维模型,通过对正常膝关节添加隧道与植入ACL移植物构建出ACL单束/双束重建膝关节模型。随后在压扭、压弯及压扭弯载荷作用下通过对ACL移植物施加10N~100N范围内的初始力进行有限元仿真,以此来分析初始力对关节软骨、半月板、移植物的应力分布影响以及对关节间接触力和关节位移的影响,所得结论如下:首先,单束/双束重建胫股关节的软骨、半月板的应力分布受初始力影响较小,其最大等效应力随初始力的变化分别不超过25%和20%,但移植物上的最大应力却随初始力的增加明显增大;其次,单束重建关节中半月板传递的轴向载荷随初始力增大而增加,双束重建关节中半月板传递载荷则随着初始力的增大反而减小;最后,在初始力10N~100N范围内,胫骨前移与所承受的前向力载荷之间基本成线性关系,前移量随初始力增大而减小。根据重建关节特性曲线表明,初始力对双束重建的影响稍微小于单束重建。     

Electron microscopic evaluation of the effects of stress-shielding on maturation of the mid-substance and ligament-bone junction of the reconstructed anterior cruciate ligament in rabbits

To analyze the effects of stress-shielding on graft maturation after the anterior cruciate ligament (ACL) reconstruction, autogenous ACL reconstruction using Achilles tendon was performed in rabbits. Two-end fixation with a ligament augmentation device (LAD), as a stress-shielding model (SS group), and pull-out fixation with Leeds-Keio artificial ligaments (L-K ligament), as a non-stress-shielding model (non-SS group), were investigated. Intact ACL was used as the control. Specimens were harvested 6 mon postoperatively, and the analysis was focused on collagen fibril maturation in the mid-substance and bone-anchoring pattern in the bone tunnel, under light and transmission electron microscopy. The density of collagen fibrils in the control was lower than that in both experimental groups (p<0.01). The per cent collagen area in the control was higher than that in the SS (p<0.01) and the non-SS group (p<0.01). The per cent collagen area in the non-SS group was higher than that in the SS group (p<0.05). At the ligament-bone interface, intracellular calcification of the degenerated chondrocytes occurred in the non-SS group, while in the SS group hydroxyapatite deposits were observed only in the extracellular matrix. These results show unfavorable influence of stress-shielding on graft maturation not only in the mid-substance but also at the ligament-bone junction. © 1999 Kluwer Academic Publishers     

Tissue response to a braided poly-L-lactide implant in an experimental reconstruction of anterior cruciate ligament

During follow-up periods of 6, 12, 24 and 48 weeks, the tissue response to a braided poly-L-lactide (PLLA) implant, 3.2 mm in diameter, was investigated in the reconstruction of experimental anterior cruciate ligament (ACL) ruptures in 32 sheep. In 16 sheep the cut ACL was removed and reconstructed with the fascia lata augmented with a PLLA implant. In 16 sheep the ACL was cut from its midportion, sutured, and thereafter augmented with a PLLA implant. The tissue reactions were typical of a scant non-specific-foreign-body reaction. The number of inflammatory and giant cells was greatest at six weeks, decreasing thereafter. Degradation of the PLLA was incomplete at 48 weeks. No signs of synovitis or changes in the cartilaginous surfaces were observed. The reconstructions in both groups were anchored to the bone by fibroconnective tissue, and remodelling of the bone was seen along the drill channels. After 48 weeks the maturation of the fibroconnective tissue and the orientation of the collagen fibres were higher (p<0.01) in the fascia-lata-PLLA group than in the primarysuture-PLLA group. Histologically, the braided PLLA implants proved to be suitable for ACL repair in sheep. The augmentation of the fascia lata with the PLLA implant seemed to be preferable to that of the primary suture of the ACL.     

超声衍射CT及其在不完全投影条件下的实验研究

超声衍射层析成像术是一种利用声波散射数据所携带的信息来反演物体内部结构的技术，具有广泛的应用前景。本文对这一领域的研究现状进行综述，慨述一些典型的超声衍射层析成像重构方法，同时探讨在残缺投影数据下的重构问题，对于不完全投影数据下的图像重构进行了实验研究。最后对实验结果进行讨论。     

用空间光调制器实现全息再现像的实时重构

针对目前实现大视角数字全息图实时动态再现的难点,提出了一种基于液晶空间光调制器用分时再现原理实现大视角数字全息图实时动态显示的新方法.分析了大视角全息图的计算原理和利用空间光调制器进行分时再现的技术原理,并提出了空间多屏拼接的方法.利用经改造的液晶背投影光学引擎系统设计了实验系统,对计算得到的全息图阵列进行了相应的处理以符合原投影系统RGB信号的传榆,处理后的全息图阵列由计算机控制以60Hz的频率输出到光学引擎.实验结果表明,可以观察到大视角全息图的动态再现像.     

声相关计程仪检测技术

声相关计程仪(Acoustic Correlation Log,ACL)检测技术用于对ACL在陆上进行功能检测。阐述了检测技术原理、检测方案以及检测平台的设计与实现。采用声呐阵对接检测的方案,可以连续对ACL完成一系列的检测。为了对70k Hz ACL进行功能检测,使用快速多通道并行的A/D、D/A模块,基于运行在PXI控制器的WINDOWS平台,开发了微软基础类库(Microsoft Foundation Classes,MFC)框架下的检测软件,搭建了完整有效的可视化检测平台。该检测平台可以完成对70 k Hz ACL的在载体功能检测,包括发射通道检测、接收通道检测以及串口输出检测等主要功能检测。检测平台使用便捷,性能稳健。经实验室测试证明,检测方案具备可行性,检测平台具有实用性。     

A non-linear stochastic approach of ligaments and tendons fractional-order hereditariness

In this study the non-linear hereditariness of knee tendons and ligaments is framed in the context of stochastic mechanics. Without losing the possibility of generalization, this work was focused on knee Anterior Cruciate Ligament (ACL) and the tendons used in its surgical reconstruction. The proposed constitutive equations of fibrous tissues involves three material parameters for the creep tests and three material parameters for relaxation tests. One-to-one relations among material parameters estimated in creep and relaxations were established and reported in the paper. Data scattering, observed with a novel experimental protocol used to characterize the mechanics of the tissue, was modelled as the outcome of the random mechanical parameters. The numerical example proposed in the paper shows that for an assigned probability density function of the material random parameters, the parameters of the probability density function (pdf) may be obtained by a statistical analysis of the experimental data.     

Collagen structure in human anterior cruciate ligament and patellar tendon

Human anterior cruciate ligaments (ACL) and patellar tendons (PT) were examined using scanning and transmission electron microscope to determine collagen architecture and morphology. Morphometric measurements were performed using an image analyser. Similarities and differences were found between the ACL and the PT. In both tissues, the anterior band is more collagenous than the posterior band giving rise to a material heterogeneity. In addition, a considerable variation in the collagen fascicle cross-sectional area was found. There was no significant difference between the ACL and PT fibre diameters, except for the elderly subjects.The collagen wave pattern was found to be helical in the PT while in the ACL it may be helical as well as planar. In addition, the waviness period was significantly larger in the PT than in the ACL. Finally, transverse fibrils, the nature of which is unknown, were found only in the ACL.