基于nmsBuilder和OpenSim建立个性化 骨肌模型及其验证

目的 利用nmsBuilder和OpenSim两款软件构建个性化全膝关节置换（total knee replacement, TKR）术后骨骼肌肉多体动力学模型,并用弹跳式和内推式两种步态对构建模型进行验证分析。方法 利用患者骨骼数据,通过nmsBuilder建立骨骼实体、骨标点和肌肉标点,从而自动生成对应参考系统和肌肉,将nmsBuilder生成的骨肌模型导入OpenSim先后执行逆向运动学、静态优化和膝关节接触力分析,最后通过弹跳式和内推式两种步态对模型进行模拟分析,并与实验测量值进行对比验证。结果 除了外侧关节接触力,模型预测的胫股关节接触力幅值和趋势与实验获得数据对比有很好的一致性,构建的骨骼肌肉多体动力学模型可以被用于膝关节研究。结论 利用患者骨骼信息建立的骨肌模型通过输入标记点位置和地面反作用力,可以同时预测出内侧、外侧以及总胫股关节接触力。研究思路可为TKR患者设计个性化膝关节假体提供参考。     

UKA 关节线安装误差对膝关节接触力学和运动学影响

目的 针对单髁膝关节置换(unicompartmental knee arthroplasty, UKA)内侧假体松动和外侧关节软骨退化问题,通过骨肌多体动力学方法研究不同生理活动中UKA关节线安装误差对膝关节接触力学和运动学的影响。方法 以内侧自然关节线为0 mm误差,分别考虑±2 mm、±4 mm、±6 mm共6种关节线安装误差情况,建立7个内侧UKA置换的骨肌多体动力学模型,对比研究步行和下蹲运动中膝关节接触力学和运动学的变化。结果 在步行步态周期70%时,相比于0 mm误差UKA假体关节线升高2 mm时内侧假体接触力增大127.3%,外侧软骨接触力减少12.0%;在UKA假体关节线降低4 mm时内侧假体接触力接近0 N,外侧软骨接触力增大10.1%;胫股关节总接触力在关节线升高和降低2 mm时分别增大19.7%和减小14.2%。在下蹲屈膝100°时,相比于0 mm误差膝关节内侧假体接触力和胫股骨关节总接触力在UKA假体关节线升高2 mm时分别增大31.6%和11.1%,在UKA假体关节线降低2 mm时分别减小24.5%和8.5%,而膝关节外侧软骨接触力变化不大。同时,在步行步态...     

基于CT和MRI膝关节有限元模型建立与不同载荷下生物力学特性分析

基于CT和MRI图像数据建立膝关节有限元模型,采用六面体网格对不同载荷系统下人体膝关节生物力学特性进行研究,并进行有效性验证。建立膝关节有限元模型包括:股骨、胫骨、髌骨、腓骨、股骨软骨、胫骨软骨、腓骨软骨、半月板、前后交叉韧带、内外侧副韧带、髌韧带和股四头肌腱等。对膝关节施加1 kN轴向压缩载荷、134 N后向抽屉力和5、10、15 N[?m内翻力矩和外翻力矩,分析膝关节内软骨和半月板的接触应力和接触面积,股骨内外翻倾角以及位移变化情况。在1 kN压缩载荷和134 N抽屉力作用下,股骨软骨、内外侧半月板和内外侧胫骨软骨的接触应力峰值分别为4.47、3.25、2.83、2.70、2.53 MPa,Von Mises应力峰值分别为2.22、2.44、2.25、2.07、1.64 MPa。股骨相对胫骨前向位移为4.19 mm。施加5、10、15 N[?m内翻和外翻力矩时,股骨内翻和外翻倾角分别为3.49°、4.48°、4.91°和3.22°、3.62°、4.01°。随着力矩的线性增大,膝关节各组成部分的应力呈非线性变化趋势。膝关节软骨、半月板和韧带的研究结果符合其生物力学特性,与前人数值分析和实验研究结果相一致,可为临床膝关节生理病理分析和治疗提供一定的理论依据。     

人体膝关节韧带生物力学研究进展

韧带是稳定膝关节的主要组成部分。如何在生物力学模型中模拟韧带将会影响膝关节动力学特性以及韧带力．韧带应变和接触力分布的计算。本文就韧带在生物力学模型中的简化方法及其力学参数的选择以作一综述．并提出建模的具体方法。     

后稳定型全膝关节假体的骨肌多体动力学研究EI北大核心CSCD

后稳定型全膝关节假体已经被广泛应用于骨科临床治疗膝骨关节炎,但是胫骨衬垫立柱的磨损、断裂以及假体松动等失效问题依然困扰着患者和医生。了解患者体内膝关节假体的生物力学特性有利于降低术后的假体翻修率和患者不满意度。本文针对6种不同后稳定型全膝关节假体分别建立了全膝关节置换的骨肌多体动力学模型,在模拟走路、右转和下蹲3种生理活动下,对比研究了6种后稳定型全膝关节假体的生物力学差异。结果表明,在走路、右转和下蹲活动中PFC Sigma和Scorpio NGR两种假体的立柱所受接触力较大,增加了立柱断裂和磨损破坏以及假体早期松动的风险。Gemini SL的螺旋型立柱设计更有利于膝关节的内外旋转运动,同时避免了立柱边沿接触磨损。后稳定型全膝关节假体矢状面较低的关节面匹配度设计和较晚的立柱-凸轮相遇接触设计将导致较大的前后平移运动。本文为临床指导医生选择、改进假体设计和降低假体失效提供了理论支撑。     

人体膝关节平地行走时的动力学模拟

基于美国BRG公司的运动及动力学仿真分析软件LifeMOD,建立包括股骨、胫骨、腓骨、4条主要韧带及肌肉在内的较完整的膝关节动力学模型,并用该模型模拟了人体下肢在平地行走时膝关节的动力学行为以及前交叉韧带缺损对膝关节接触力大小的影响。通过动力学分析,得到人体在平地行走时,胫股关节之间最大的接触力值为2645N,最大韧带张力为590N,发生在内侧副韧带上;当胫股关节之间的滑动受到限制时,最大的韧带张力发生在前交叉韧带上,为560N,研究结果与文献较接近。通过动力学模拟,可以得出结论：胫股关节之间的滑动对韧带张力有较大影响;前交叉韧带缺损使得胫股关节之间的接触力变小。     

膝骨性关节炎合并内翻畸形患者运动特征研究

为研究膝骨性关节炎合并内翻畸形患者术前生物力学群体特征,用于比较患者术前术后步态延续性及进行术后康复指导,本文采集9例患者水平行走和坐立-起身过程的步态,并进行骨肌多体动力学分析。本文研究结果显示,水平行走时试验组下肢运动功能减弱,试验组非手术侧膝关节平均活动范围为22.5°~71.5°,拟置换侧膝关节平均活动范围为24.4°~57.6°,而对照组膝关节平均活动范围为7.2°~62.4°。单侧膝内翻患者完成坐立-起身过程时的下肢地面反作用力对称度介于0.72~0.85,非手术侧下肢起主要支撑作用。双侧膝内翻患者坐立-起身时地面反作用力之和最小。尽管单侧膝内翻患者采用非手术侧下肢过量负载的代偿方式能完成术后日常活动,但长期过量负载容易增加非手术侧下肢膝关节罹患膝骨性关节炎风险。对膝骨性关节炎合并内翻畸形患者完成日常活动的运动学和生物力学特征进行研究,有助于从生物力学角度理解内翻膝的发病机制,对患者的术前评估、预防和术后恢复具有较强的临床指导意义。     

有限元法预测运动护膝在不同运动状态下对膝关节韧带的影响

背景：膝关节韧带是维持膝关节运动稳定性的重要组成部分,在人体运动过程中极易受到损伤,运动护膝常用于预防膝关节运动损伤,但其防护性能未能明确。目的：建立健康成年人的膝关节有限元模型及运动护膝模型,运用有限元法预测运动护膝在不同运动状态下对膝关节韧带的影响,以Von Mises等效应力为观察指标,探讨不同材料运动护膝的防护性能。方法：以1名男性健康志愿者的CT影像为数据来源,利用Mimics、Solidworks、Abaqus等软件获得膝关节有限元模型及运动护膝模型;以股骨内外髁中点为参考点施加后向134 N集中力,模拟临床前抽屉实验,获取股骨相对位移及主要韧带的生物力学响应,验证膝关节模型的有效性;给运动护膝施加位移载荷,模拟膝关节直立位穿着护膝的状态,并与服装压力测试结果进行对比,验证膝关节-护膝模型的有效性;分别在无护膝和两种不同材料护膝作用下模拟膝关节屈曲0°,30°,60°运动,分析不同载荷下前交叉韧带、后交叉韧带、内侧副韧带及外侧副韧带的应力应变情况。结果与结论：(1)在0°,30°,60°屈曲角度下,并且施加320 N垂直压缩力及134 N股骨后向推力后,相较于裸膝,穿着两种...     

一种液体弹簧式自身力源膝关节助力矫形器的设计思路与生物力学分析EI北大核心CSCD

本文设计并制造了一款微型硅油液体弹簧,并通过仿真分析与力学实验对微型硅油液体弹簧的性能进行了研究。基于此微型硅油液体弹簧设计了一款自身力源膝关节助力矫形器,能够将膝关节屈曲的动能转换为膝关节助力矫形器中微型硅油液体弹簧的弹性势能进行存储,在膝关节伸展时弹性势能释放转换为驱动膝关节的辅助力矩。结果显示,本文所制造微型硅油液体弹簧平均最大复位力为1240 N,产生的膝关节平均最大辅助力矩为29.8 N·m。然后,本文通过使用人体骨骼肌肉多体动力学模型,分析了人体下蹲过程中(膝关节屈曲90°),膝关节助力矫形器对膝关节生物力学所产生的影响。结果显示,对于体重为80 kg的使用者而言,膝关节助力矫形器可以有效降低膝关节的生物力学负荷,其中股骨-胫骨的膝关节力、髌骨-股骨髁的作用力以及股四头肌-韧带力的最大值分别降低了24.5%、23.8%与21.2%。本文所设计的膝关节助力矫形器不仅可以为膝关节提供充足的辅助力矩,同时具备体积小、重量轻的优势,可为后续的商业化应用奠定基础。     

不同股骨止点对内侧髌股韧带重建后髌股关节应力影响的三维有限元分析

背景：髌股韧带重建有多种手术方式,其中股骨止点选取对手术实施影响较大,目前针对股骨止点的选取有多种方式,但无定论。目的：通过三维有限元软件分析膝关节不同屈曲状态下内侧髌股韧带（MPFL）股骨重建止点位置改变对髌股关节应力的影响,从而选择出合理准确的股骨重建止点。方法：获取成年人正常膝关节CT数据,导入Mimics、Geomagic及Soildworks软件进行提取模具、添加韧带,其中韧带的股骨止点选择分别为股骨内上髁与内收肌结节连线的中点、股骨内上髁、内收肌结节、股骨髁间窝顶部向内髁投射点和内收肌结节下10 mm,再将添加韧带后的模具导入机械软件Ansys,对不同股骨止点重建后髌股关节应力进行生物力学的有限元分析。结果与结论：（1）在膝关节屈曲0°和30°时,选取任一股骨止点产生的髌股关节应力大于其他屈曲角度（60°,90°,120°）;无论采取哪种位点作为股骨端止点,当膝关节屈曲超过30°时,髌股关节间的接触应力大小基本无差别;（2）在膝关节屈曲0°和30°时,以内收肌结节为止点的髌股接触压力最大,以股骨内上髁与内收肌结节连线的中点为止点的接触力最小;在膝关节屈曲30°时,股骨内上髁...     

Differences in impact on adjacent compartments in medial unicompartmental knee arthroplasty versus high tibial osteotomy with identical valgus alignment

BackgroundIt is unclear why medial unicompartmental knee arthroplasty (UKA) with postoperative valgus alignment causes adjacent compartment osteoarthritis more often than high tibial osteotomy (HTO) for moderate medial osteoarthritis of the knee with varus deformity. This study used a computer simulation to evaluate differences in knee conditions between UKA and HTO with identical valgus alignment.MethodsDynamic musculoskeletal computer analyses of gait were performed. The hip–knee–ankle angle in fixed-bearing UKA was changed from neutral to 7° valgus by changing the tibial insert thickness. The hip–knee–ankle angle in open-wedge HTO was also changed from neutral to 7° valgus by opening the osteotomy gap.ResultsThe lateral tibiofemoral contact forces in HTO were larger than those in UKA until moderate valgus alignments. However, the impact of valgus alignment on increasing lateral forces was more pronounced in UKA, which ultimately demonstrated a larger lateral force than HTO. Valgus alignment in UKA caused progressive ligamentous tightness, including that of the anterior cruciate ligament, resulting in compression of the lateral tibiofemoral compartment. Simultaneously, patellofemoral shear forces were slightly increased and excessive external femoral rotation against the tibia occurred due to the flat medial tibial insert surface and decreased lateral compartment congruency. By contrast, only lateral femoral slide against the tibia occurred in excessively valgus-aligned HTO.ConclusionsIn contrast to extra-articular correction in HTO, which results from opening the osteotomy gap, intra-articular valgus correction in UKA with thicker tibial inserts caused progressive ligamentous tightness and kinematic abnormalities, resulting in early osteoarthritis progression into adjacent compartments.     

Consistency Among Musculoskeletal Models: Caveat Utilitor

Musculoskeletal simulation software and model repositories have broadened the user base able to perform musculoskeletal analysis and have facilitated in the sharing of models. As the recognition of musculoskeletal modeling continues to grow as an engineering discipline, the consistency in results derived from different models and software is becoming more critical. The purpose of this study was to compare eight models from three software packages and evaluate differences in quadriceps moment arms, predicted muscle forces, and predicted tibiofemoral contact forces for an idealized knee-extension task spanning ?125 to +10° of knee extension. Substantial variation among models was observed for the majority of aspects evaluated. Differences among models were influenced by knee angle, with better agreement of moment arms and tibiofemoral joint contact force occurring at low to moderate knee flexion angles. The results suggest a lack of consistency among models and that output differences are not simply an artifact of naturally occurring inter-individual differences. Although generic musculoskeletal models can easily be scaled to consistent limb lengths and use the same muscle recruitment algorithm, the results suggest those are not sufficient conditions to produce consistent muscle or joint contact forces, even for simplified models with no potential of co-contraction.     

A non-invasive measurement of the knee contact force using a subject-specific musculoskeletal model to investigate osteotomy

The varus knee has been defined as a Hip-Knee-Ankle alignment of less than 180 degrees. Varus knee alignment increases the load on the medial knee and also the risk of osteoarthritis. High tibial osteotomy has been designed to modify the malalignment of varus knee. The aim of this study was to investigate the osteotomy effects on knee adduction moment (KAM) and contact forces using a musculoskeletal and subject-specific knee model. A patient with varus knee and no symptoms of any other disease or disability participated in this study. The geometry of the multibody knee model has been modified using MR images. The solutions of its finite element model have been used to determine the parameters of the multibody model. The motion data, ground reaction force and kinetic data have been applied to run the subject-specific musculoskeletal model during the stance phase of gait. After osteotomy, the adduction moment decreased, where the maximum values are comparable to other studies. The pattern of KAM did not witness any significant changes. The total and medial contact forces reduced considerably after surgery, but the lateral contact force did not significantly change. The changes in total and medial contact forces and lack of change in lateral contact force could be explained by modification of the gait pattern after surgery.     

Evaluation of a musculoskeletal model with prosthetic knee through six experimental gait trials

Knowledge of the forces acting on musculoskeletal joint tissues during movement benefits tissue engineering, artificial joint replacement, and our understanding of ligament and cartilage injury. Computational models can be used to predict these internal forces, but musculoskeletal models that simultaneously calculate muscle force and the resulting loading on joint structures are rare. This study used publicly available gait, skeletal geometry, and instrumented prosthetic knee loading data [1] to evaluate muscle driven forward dynamics simulations of walking. Inputs to the simulation were measured kinematics and outputs included muscle, ground reaction, ligament, and joint contact forces. A full body musculoskeletal model with subject specific lower extremity geometries was developed in the multibody framework. A compliant contact was defined between the prosthetic femoral component and tibia insert geometries. Ligament structures were modeled with a nonlinear force–strain relationship. The model included 45 muscles on the right lower leg. During forward dynamics simulations a feedback control scheme calculated muscle forces using the error signal between the current muscle lengths and the lengths recorded during inverse kinematics simulations. Predicted tibio-femoral contact force, ground reaction forces, and muscle forces were compared to experimental measurements for six different gait trials using three different gait types (normal, trunk sway, and medial thrust). The mean average deviation (MAD) and root mean square deviation (RMSD) over one gait cycle are reported. The muscle driven forward dynamics simulations were computationally efficient and consistently reproduced the inverse kinematics motion. The forward simulations also predicted total knee contact forces (166 N < MAD < 404 N, 212 N < RMSD < 448 N) and vertical ground reaction forces (66 N < MAD < 90 N, 97 N < RMSD < 128 N) well within 28% and 16% of experimental loads, respectively. However the simplified muscle length feedback control scheme did not realistically represent physiological motor control patterns during gait. Consequently, the simulations did not accurately predict medial/lateral tibio-femoral force distribution and muscle activation timing.     

In-situ forces in the human posterior cruciate ligament in response to posterior tibial loading

Although some investigators have referred to the human posterior cruciate ligament (PCL) as the center of the knee, it has received less attention than the more frequently injured anterior cruciate ligament (ACL) and medial collateral ligament (MCL). Therefore, our understanding of the function of the PCL is limited. Our laboratory has developed a method of measuring thein-situ forces in a ligament without contacting that ligament by using a universal force-moment sensor (UFS). In this study, we attached a USF to the tibia and measuredin-situ forces of the human PCL as a function of knee flexion in response to tibial loading. At a 50-N posterior tibial load, the force in the PCL increased from 25±11 N (mean±SD) at 30° of knee flexion to 48±12 N at 90° of knee flexion. At 100 N, the corresponding increases were to 50±17 N and 95±17 N, respectively. Of note, at 30° knee flexion, approximately 45% of the resistance to posterior tibial loading was caused by contact between the tibia and the femoral condyles, whereas, at 90° of knee flexion, no resistance was caused by such contact. For direction of thein-situ force, the elevation angle from the tibial plateau was greater at 30° of knee flexion than at 90° of knee flexion. The data gathered on the magnitude and direction of thein-situ force of the PCL should help in our understanding of the dependence of knee flexion angle of the forces within the PCL.     

Interpreting Musculoskeletal Models and Dynamic Simulations: Causes and Effects of Differences Between Models

With more than 29,000 OpenSim users, several musculoskeletal models with varying levels of complexity are available to study human gait. However, how different model parameters affect estimated joint and muscle function between models is not fully understood. The purpose of this study is to determine the effects of four OpenSim models (Gait2392, Lower Limb Model 2010, Full-Body OpenSim Model, and Full Body Model 2016) on gait mechanics and estimates of muscle forces and activations. Using OpenSim 3.1 and the same experimental data for all models, six young adults were scaled in each model, gait kinematics were reproduced, and static optimization estimated muscle function. Simulated measures differed between models by up to 6.5° knee range of motion, 0.012 Nm/Nm peak knee flexion moment, 0.49 peak rectus femoris activation, and 462 N peak rectus femoris force. Differences in coordinate system definitions between models altered joint kinematics, influencing joint moments. Muscle parameter and joint moment discrepancies altered muscle activations and forces. Additional model complexity yielded greater error between experimental and simulated measures; therefore, this study suggests Gait2392 is a sufficient model for studying walking in healthy young adults. Future research is needed to determine which model(s) is best for tasks with more complex motion.     

Kinematic analysis of mobile-bearing and fixed-bearing knee prostheses by simulation

The object of the study was to model fixed-bearing knee prostheses (FBKs) and mobile-bearing knee prostheses (MBKs) during weight-bearing deep knee bends and to analyse and compare the kinematics of the two prosthesis types. To obtain quantitative data, an overall model of a leg was constructed, and this included a three-dimensional model of the tibiofemoral joint and simplified twodimensional models of the ankle and patellofemoral joint. The simulated movement pattern of the tibiofemoral contact point in the FBK was analysed to show the posterior contact position on the tibia at full extension and anterior translation as the knee was flexed from 30° to 90°. The simulated maximum displacements of the medial and lateral contact positions of the FBK were 5.6 and 6.2 mm, respectively. These results were almost in agreement with experimental studies. Compared with the FBK, the movement pattern of the tibiofemoral contact point in the MBK for the anterior contact position on the tibia at full extension and posterior translation, with respect to the tibia as the knee was flexed, gave results closer to those of the normal knee. The simulated displacements of the medial and lateral contact positions of the MBK with respect to the tibia were 9.0 and 13.0 mm from full extension to 90° flexion, respectively. The difference in the kinematic results between the FBK and the MBK could be accounted for by movement of the insert and the larger force of the posterior cruciate ligament on the MBK.     

Estimation of bone-on-bone contact forces in the tibiofemoral joint during walking

In this study, the tibiofemoral contact forces were estimated from standard gait analysis data of adult walking. Knee angles, ground reaction forces, and external flexion-extension knee moments together with lines of action and moment arms of the force bearing structures in the knee previously determined were used to obtain bone-on-bone contact forces. The heel strike, the onset of single limb stance and terminal extension before toe-off each corresponded to a significant turning point on the force versus gait cycle curve. The tibiofemoral bone-on-bone peak forces calculated reached an estimated three times bodyweight. The estimated joint loads are clinically relevant and can either be used directly for evaluation of subjects in a gait analysis, or indirectly in studies of the knee joint where models simulating loading conditions are used to investigate various pathologies.