有限元法分析下颈椎侧屈-轴向旋转的运动耦合关系

[目的]探讨下颈椎旋转-侧屈的耦合运动相互关系.[方法]获取CT扫描图像数据,应用Mimics 10.01、Geomagic studio10.0、HyperMesh10.0、Abaqus 6.9.1等软件建立和验证下颈椎三维有限元模型,并对其测定在侧屈模拟状态下的节间旋转角度.[结果]建成后模型具有较好的几何相似性.实验共生成177 944个单元,35 668个节点.加载后以其颈椎各种模拟状态下的节间运动范围(角度)为指标,与实验实测结果相比较,表明该有限元模型的有效性.在侧屈模拟状态下,对其模型进行节间旋转角度的测定,结果表明颈椎具有明显的耦合特征,即侧屈时伴有明显的轴向旋转运动.[结论]利用数字图像技术、逆向工程、三维有限元的方法相结合,建立下颈椎(C3～7)三维有限元模型,为后续的下颈椎运动学研究提供了新思路.     

高原颈椎前路椎间融合后不同固定方式的生物力学特性的研究

[目的]分析比较颈椎前路椎间融合后不同固定方式的生物力学特性.[方法]建立正常高原人C5/6的三维有限元模型.利用有限元软件ANSA13.0.2对模型进行有限元网格划分,最后加入韧带和关节囊,通过模拟前路手术摘除椎间盘建立椎间植骨融合的有限元模型,加入前路内固定器及后路椎弓根系统三种三维有限元模型.各模型施加前屈/后伸,左/右侧弯,左/右旋转6种生理载荷,模拟颈椎6个方向的生理活动.[结果]前路和后路2种固定方式均明显减少了前路椎体融合植骨块的应力,后路固定较前路固定更减少了植骨块的应力.主要的应力集中在椎体和螺钉交界处,不同方向运动上下螺钉承受的应力没明显差异.[结论]前路椎体间融合后通过前路和后路固定均可以降低植骨块的应力,达到手术后的初始稳定性,后路椎弓根固定在前路融合后其生物力学的稳定性强于前路钢板固定.     

上颈椎三维非线性有限元模型的建立及其有效性验证

目的建立具有详细解剖结构的上颈椎三维非线性有限元模型并验证其有效性。方法对健康成年男性志愿者进行CT扫描,获得枕骨底(C0)到C3的体层图像,将数据导入Mimics软件进行上颈椎骨质的三维模型重建,用Freeform软件进行模型修改,导入有限元软件Ansys9.0进行分析计算。模型中韧带以非线性的弹性元素建模,分为弹性区和中性区,分别定义元素性质,韧带的起止点及横截面积根据文献确定,寰椎横韧带坚韧、弹性低,定义为固体元素性质,同时便于对齿状突横韧带关节进行受力分析。寰枕关节、寰枢关节、C2,3关节突关节、寰椎齿状突关节、齿状突横韧带关节均定为有摩擦系数的表面滑动接触关节。使模型C3椎体下缘固定,在枕骨底施加40N的预载荷和1.5N·m的力矩作用下使其产生前屈、后伸、旋转、侧屈运动,将模型的活动度(ROM)与Panjabi测得正常上颈椎的实验数据对比进行验证。结果建立了具有详细解剖结构的上颈椎三维非线性有限元模型,整个模型有229047个节点和152475个单元,模型运动范围与Panjabi的数据相符合。结论建立的上颈椎模型具有较高的真实性,可以用于生物力学分析实验。     

齿状突Ⅱ型骨折三维有限元模型的建立

目的 建立具有详细解剖结构的上颈椎齿状突Ⅱ型骨折(C0-3)三维非线性有限元模型.方法 将CT体层扫描图像导入Mimics软件进行上颈椎三维模型重建,横行去除齿状突基底部骨质,模拟齿状突Ⅱ型骨折.导入有限元软件Ansys 9.0进行分析计算.模型中韧带以非线性的弹性元素建模,分为弹性区和中性区,分别定义元素性质,韧带的起止点及横截面积根据文献确定.在枕骨底施加40N的预载荷和1.5 Nm的力矩使其产生前屈、后伸、旋转、侧屈运动,将模型的活动度(ROM)与齿状突Ⅱ型骨折的体外实验结果对比进行验证.结果 模型有229 047个节点和152 475个单元,寰枢节段运动范围:屈伸38.3度,侧屈20.4度,旋转74.2度,与体外实验结果相符合.结论 建立的上颈椎齿状突Ⅱ型模型具有较高的真实性,可以用于生物力学分析实验.     

寰枢椎脱位三维非线性有限元模型的建立和分析

目的:探索寰枢椎脱位有限元模型的建模方法及其在寰枢椎脱位临床治疗中的作用.方法:在正常上颈椎三维非线性有限元模型的基础上结合临床实际寰枢惟脱位病例,应用有限元软件,建立横韧带断裂而不伴有齿状突骨折的寰枢椎前脱位有限元模型,进行有限元分析,测量并比较正常上颈椎模型和寰枢椎脱位模型在屈、伸、侧屈、旋转等工况下的活动度(ROM).结果:在正常上颈椎三维非线性有限元模型的基础上结合临床实际寰枢椎脱位病例建立的横韧带断裂不伴齿状突骨折的寰枢椎前脱位有限元模型外观逼真,几何相似性好,各个工况下的活动度较正常上颈椎模型明显增大,尤其是前屈增加了17.8°,后伸增加了13.7°.结论:寰枢椎脱位非线性三维有限元模型能够较好地模拟临床实际脱位病例,可用于临床对寰枢椎脱位患者的生物力学分析,从而指导制定寰枢椎脱位的治疗策略.     

利用Mimics和Freeform建立下颈椎三维非线性有限元模型

目的建立具有详细解剖结构的下颈椎三维非线性有限元模型并验证其有效性。方法对健康成年男性志愿者进行CT扫描,获得C4-7,节段的断层图片,将数据保存为Dicom格式,导入Mimics9．1软件进行三维几何模型重建,形成三维图像,利用Freeform软件进行模型修改和表面划分,以IGES格式转入有限元软件Ansys9．0完成有限元模型建模。下颈椎韧带以非线性的弹性元素建模,韧带的起止点及横截面积根据文献确定,关节突关节定义为有摩擦系数、表面滑动接触关系。在C4施加40N的预载荷,在1．8N·m的力矩作用下使模型产生前屈、后伸、侧屈、旋转运动,将实验结果与Moroney等实验结果对比进行验证。结果建立了具有详细解剖结构的下颈椎三维非线性有限元模型。整个模型共有145570个节点,96645个单元,模型在各种工况下的平均刚度与Moroney等的结果基本吻合。结论利用Mimics和Freeform建立的下颈椎模型在一定条件下是有效的,可以进行临床和实验研究。     

带肌肉组织全颈椎三维有限元模型的建立及分析

目的 :建立带肌肉组织的全颈椎三维有限元模型并验证该模型的有效性,为进一步分析颈椎疾患的生物力学作用机制建立良好的工作平台。方法:选取一名34岁健康男性志愿者进行颈椎薄层CT扫描,将CT原始数据以Dicom格式存贮。用Mimics 17软件将CT图像逆向重建出颈椎三维点云模型,利用Geomagic Studio 2012软件把点云模型拟合成NURBS曲面模型,然后导入Hypermesh12软件中进行网格划分、赋予材料属性、定义接触及边界条件等操作,最后提交至ABAQUS 6.12软件进行有限元分析,将各个工况(前屈、后伸、侧弯和轴向旋转)下各节段活动度与文献数据进行比较,验证该模型有效性。结果:建立的带有肌肉组织的全颈椎三维有限元模型共包含789024单元,285045节点,外观与人体颈椎具有非常好的几何相似性。该模型在屈伸、侧弯及旋转工况下的活动度与文献数据进行了80次对比,共计24次(占30%)超出部分参考范围,其中,仅C5-6左右侧弯活动度8.4°、C0-C1左右旋转活动度24.2°超出所有参考范围(P0.05)。结论:本研究建立的带有肌肉组织的全颈椎三维有限元模型符合有限元分析几何相似性和力学相似性要求,可用于颈椎生物力学分析。     

下颈椎全椎板切除后生物力学特性改变机制的有限元分析

目的:探讨下颈椎全椎板切除后生物力学特性改变的机制。方法:采集1例成年健康男性志愿者下颈椎(C3～C7)的CT数据集,应用Mimics 10.01、Geomagic studio 10.0、HyperMesh 10.0、Abaqus 6.9.1等软件建立下颈椎(C3～C7)完整有限元模型、完整保留双侧关节突关节三节段(C4～C6)全椎板切除后有限元模型。模拟施加74N头颅预载荷和1.8Nm运动附加力矩,使模型产生前屈、后伸、侧屈和旋转运动,测试颈椎全椎板切除前后的运动范围和关节囊韧带、后纵韧带在各种加载方式下的拉力。结果:C4～C6全椎板切除后即刻颈椎屈伸、侧弯和旋转的运动范围与完整状态下比较均没有增加,但C4～C6节段之间的关节囊韧带和后纵韧带在各种加载方式下受到的拉力均增大。结论:完整保留双侧关节突关节的全椎板切除术不会对下颈椎即时稳定性造成影响,但关节囊韧带和后纵韧带承受着超正常生理负荷。     

颈椎后纵韧带骨化椎间盘及后纵韧带应力的有限元分析

[目的]探讨颈椎后纵韧带骨化(OPLL)椎间盘及后纵韧带应力的变化。[方法]选择C4/5节段孤立型、混合型和节段型OPLL患者和正常人各1例行CT扫描,采用Mimics 14.0、Geomagic Studio 10.0和Hypermesh11.0软件对数据进行处理,建立有限元模型。采用Abaqus 6.12软件计算在前屈、后伸、旋转位载荷下椎间盘及后纵韧带的Von Mises应力。[结果]前屈和旋转载荷下,正常组C4/5、C5/6椎间盘应力显著小OPLL 3组(P0.05)。孤立型、连续混合型的C4/5、C5/6椎间盘应力显著小于节段型(P0.05)。前屈及旋转载荷下,正常组后纵韧带应力显著小于OPLL 3组(P0.05)。孤立型和混合型C4/5、C5/6节段后纵韧带应力显著大于节段模型(P0.05)。单开门成形术前与术后比较,C4/5、C5/6椎间盘及后纵韧带应力无显著改变(P0.05)。[结论]孤立型和混合型后纵韧带骨化的后纵韧带应力显著大于节段型,颈椎后路单开门不改变椎间盘与后纵韧带的受力状态。     

双节段颈前路椎间盘切除融合术应用零切迹系统或钢板联合融合器固定后颈椎生物力学变化的三维有限元研究

目的：通过三维有限元分析法比较双节段颈椎前路椎间盘切除融合术（anterior cervical discectomy and fusion,ACDF）应用零切迹（zero-profile,ZP）系统与钢板联合融合器（cage-and-plate,CP）固定后颈椎的生物力学变化。方法：采集1例正常成年女性志愿者颈椎C3～C7节段CT扫描数据,建立C3～C7颈椎有限元模型并通过对比前期研究验证模型有效性。ZP固定模型与CP固定模型的手术节段均设定为C4/5与C5/6节段。在C3椎体上方施加轴向压缩负荷73.6N的模拟重力,并逐步施加1.8N·m的转矩,进而模拟屈伸、侧屈及轴向旋转等颈椎运动。测定并比较手术模型融合节段活动度（range of motion,ROM）、邻近节段椎间盘内应力、C5椎体及融合器装置应力。结果：CP固定模型融合节段的ROM在屈伸、侧屈、旋转位均明显小于ZP固定模型;CP固定模型相邻节段（C3/4、C6/7）的椎间盘内应力均远远高于ZP固定模型,两种模型融合节段上方的椎间盘内应力均高于融合节段下方;各工况下,ZP固定模型的C5椎体应力均明显高于CP固定模型,在前屈位...     

Presenteeism and Absenteeism Before and After Total Hip and Knee Arthroplasty

BackgroundAbsenteeism is costly, yet evidence suggests that presenteeism—illness-related reduced productivity at work—is costlier. We quantified employed patients’ presenteeism and absenteeism before and after total joint arthroplasty (TJA).MethodsWe measured presenteeism (0-100 scale, 100 full performance) and absenteeism using the World Health Organization’s Health and Work Performance Questionnaire before and after TJA among a convenience sample of employed patients. We captured detailed information about employment and job characteristics and evaluated how and among whom presenteeism and absenteeism improved.ResultsIn total, 636 primary, unilateral TJA patients responded to an enrollment email, confirmed employment, and completed a preoperative survey (mean age: 62.1 years, 55.3% women). Full at-work performance was reported by 19.7%. Among 520 (81.8%) who responded to a 1-year follow-up, 473 (91.0%) were still employed, and 461 (88.7%) had resumed working. Among patients reporting at baseline and 1 year, average at-work performance improved from 80.7 to 89.4. A Wilcoxon signed-rank test indicated that postoperative performance was significantly higher than preoperative performance (P < .0001). The percentage of patients who reported full at-work performance increased from 20.9% to 36.8% (delta = 15.9%, 95% confidence interval = [10.0%, 21.9%], P < .0001). Presenteeism gains were concentrated among patients who reported declining work performance leading up to surgery. Average changes in absences were relatively small. Combined, the average monthly value lost by employers to presenteeism declined from 15.3% to 8.3% and to absenteeism from 16.9% to 15.5% (ie, mitigated loss of 8.4% of monthly value).ConclusionAmong employed patients before TJA, presenteeism and absenteeism were similarly costly. After, employed patients reported increased performance, concentrated among those with declining performance leading up to surgery.     

The German emergency and disaster medicine and management systemdhistory and present

As well for optimized emergency management in individual cases as for optimized mass medicine in disaster management, the principle of the medical doctors approaching the patient directly and timely, even close to the site of the incident, is a long-standing marker for quality of care and patient survival in Germany. Professional rescue and emergency forces, including medical services, are the “Golden Standard” of emergency management systems. Regulative laws, proper organization of resources, equipment, training and adequate delivery of medical measures are key factors in systematic approaches to manage emergencies and disasters alike and thus save lives. During disasters command, communication, coordination and cooperation are essential to cope with extreme situations, even more so in a globalized world. In this article, we describe the major historical milestones, the current state of the German system in emergency and disaster management and its integration into the broader European approach.     

Differences in Osteocyte Density and Bone Histomorphometry Between Men and Women and Between Healthy and Osteoporotic Subjects

Bone defects related to osteoporosis develop with increasing age and differ between males and females. It is currently thought that the bone remodeling process is supervised by osteocytes in a strain-dependent manner. We have shown an altered response of osteocytes from osteoporotic patients to mechanical loading, and osteocyte density is reduced in osteoporotic patients, which might relate to imperfect bone remodeling, leading to lack of bone mass and strength. Hence, information on osteocyte density will contribute to a better understanding of bone biology in males and females and to the assessment of osteoporosis. Osteocyte density as well as conventional histomorphometric parameters of trabecular bone were determined in cancellous iliac crest bone of healthy postmenopausal women and men and of osteoporotic women and men. Osteocyte density was higher in healthy females than in healthy males and lower in osteoporotic females than in healthy females. Bone mass was reduced in osteoporotic patients, both male and female. In females, trabecular number was reduced, whereas in males, trabecular thickness was reduced and eroded surface was increased. There were no correlations between the parameter groups bone architecture, bone formation, bone resorption, and osteocyte density. These results are consistent with impaired osteoblast function in osteoporotic patients and with a different mechanism of bone loss between men and women, in which osteocyte density might play a role. The reduced osteocyte numbers in female osteoporotic patients might relate to imperfect bone remodeling leading to lack of bone mass and strength. M. G. Mullender and S. D. Tan contributed equally to this work.     

Tendon and Ligament Healing and Current Approaches to Tendon and Ligament Regeneration

Ligament and tendon injuries are common problems in orthopedics. There is a need for treatments that can expedite nonoperative healing or improve the efficacy of surgical repair or reconstruction of ligaments and tendons. Successful biologically-based attempts at repair and reconstruction would require a thorough understanding of normal tendon and ligament healing. The inflammatory, proliferative, and remodeling phases, and the cells involved in tendon and ligament healing will be reviewed. Then, current research efforts focusing on biologically-based treatments of ligament and tendon injuries will be summarized, with a focus on stem cells endogenous to tendons and ligaments. Statement of clinical significance: This paper details mechanisms of ligament and tendon healing, as well as attempts to apply stem cells to ligament and tendon healing. Understanding of these topics could lead to more efficacious therapies to treat ligament and tendon injuries. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:7–12, 2020