The femoral stem is a critical implant in total hip arthroplasty; however, conventional designs often suffer from mechanical mismatch with the host bone. This study aimed to propose a rapid design strategy for re-entrant metamaterials with tailored mechanical properties, which was applied to the development of patient-specific femoral stems. A total of 300 reentrant lattice structures (16 mm × 16 mm × 16 mm) were developed by varying the re-entrant angle (θ: 50°–90°), the side length of the strut cross section (t: 0.36–1.09 mm), and compression direction (d: y or z axis). Stress-strain curves from quasi-static compression tests were used to train a back propagation neural network (BPNN) model, where 31 characteristic stress values and Poisson’s ratio served as input parameters, and θ, t, and d as output parameters. Predictive performance of the BPNN model was evaluated using the root mean square error (RMSE) and the coefficient of determination (R2). The well-trained BPNN model was then applied to match the mechanical properties of the cancellous bone obtained from subject-specific finite element analysis, thereby identifying the adaptive re-entrant structure for designing the lateral configuration of the femoral stem. The BPNN model achieved high predictive accuracy (RMSE ≤ 3.09°, R2 ≥ 0.92 for θ, RMSE = 0.04 mm, R2 ≥ 0.96 for t, and 100
Heart failure is often accompanied by myocardial dysfunction and cardiac structural remodeling. However, the lack of a comprehensive numerical framework that integrates both electrical and mechanical processes limits our understanding of how structural and material changes drive heart failure progression. Therefore, we developed and validated advanced numerical methods capable of accurately simulating the electromechanical behavior of the heart. We explored and discussed several pathophysiological models of heart failure through comprehensive whole-heart numerical simulations. A full four-chamber heart model, incorporating modified equations for electrical signal diffusion and electromechanical coupling, was employed to achieve more complete and reliable calculations of cardiac active contraction. The computational methods utilized in this study are thoroughly discussed and validated against experimental and clinical data to ensure reliability. Subsequently, different left ventricular dilation models with varying degrees of hypertrophy, along with two pathological myocardial remodeling models representing material property alterations, were developed, and their numerical results were compared and analyzed. The findings confirm that left ventricular dilation impairs diastolic function and, at the numerical level, emphasize that myocardial material properties are critical factors influencing the heart’s pumping function. Mechanically, the study elucidates how structural and material changes contribute to heart failure and demonstrates the applicability and value of the proposed models and computational methods in studying structural heart diseases. These findings offer a fresh perspective on the pathological mechanisms of heart failure, shedding light on the complex interplay between structural and material changes within the heart muscle.
Sustained high overloads often acting during aerospace flights can significantly affect the passenger brain function dependent on the mechanical behavior of brain tissue and highly correlated with load characteris-tics.To predict the mechanical responses of human brain under sustained high overloads,the poroelastic con-stitutive model was adopted to characterize the mechanical behaviors of brain tissue.Built on an idealized 1D multi-layer structural model for human heads,the poroelastic control equation and the state transfer matrix for the brain tissue were derived.Through the Laplace transform and its inverse transform,the spatiotemporal dis-tribution of the intracranial fluid pressure,the intracranial fluid seepage velocity,the brain tissue effective stress,and the brain tissue displacement were obtained.The results indicate that,the intracranial fluid infiltra-tion has a significant impact on the responses of the brain tissue under sustained high overloads.The present work emphasizes the appropriateness and necessity of using poroelastic constitutive models to describe the me-chanical behavior of brain tissue,providing important theoretical insights for the study of brain biomechanics under extreme load conditions.
Magnesium alloy, as a new material for vascular stents, possesses excellent mechanical properties, biocompatibility, and biodegradability. However, the mechanical properties of magnesium alloy stents exhibit relatively inferior performance compared to traditional metal stents with identical structural characteristics. Therefore, improving their mechanical properties is a key issue in the development of biodegradable magnesium alloy stents. In this study, three new stent structures (i.e., stent A, stent B, and stent C) were designed based on the typical structure of biodegradable stents. The changes made included altering the angle and arrangement of the support rings to create a support ring structure with alternating large and small angles, as well as modifying the position and shape of the link. Using finite element analysis, the compressive performance, expansion performance, bending flexibility performance, damage to blood vessels, and hemodynamic changes of the stent were used as evaluation indexes. The results of these comprehensive evaluations were utilized as the primary criteria for selecting the most suitable stent design. The results demonstrated that compared to the traditional stent, stents A, B, and C exhibited improvements in radial stiffness of 16.9%, 15.1%, and 37.8%, respectively; reductions in bending stiffness of 27.3%, 7.6%, and 38.1%, respectively; decreases in dog-boning rate of 5.1%, 93.9%, and 31.3%, respectively; as well as declines in the low wall shear stress region by 50.1%, 43.8%, and 36.2%, respectively. In comparison to traditional stents, a reduction in radial recoiling was observed for stents A and C, with decreases of 9.3% and 7.4%, respectively. Although there was a slight increase in vessel damage for stents A, B, and C compared to traditional stents, this difference was not significant to have an impact. The changes in intravascular blood flow rate were essentially the same after implantation of the four stents. A comparison of the four stents revealed that stents A and C exhibited superior overall mechanical properties and they have greater potential for clinical application. This study provides a reference for designing clinical stent structures.
The treatment of ovarian cancer remains a medical challenge and its malignant progression is connected with obvious changes in both tissue and cell stiffness. However, the accurate mechanical-responsive molecules and mechanism remains unclear in ovarian cancer. Based on our previous results combined with the crucial regulatory role of STAT3 in the malignant progression of various cancer types, we want to investigate the relationship between STAT3 and matrix stiffness in ovarian cancer and further explore the potential mechanisms. Collagen-coated polyacrylamide gels (1, 6, and 60 kPa) were prepared to mimic soft or hard matrix stiffness. Western blotting, qRT-PCR, flow cytometry, IHC, EdU assays, and TEM were used to evaluate the effect of STAT3 in vitro under different matrix stiffnesses. Furthermore, a BALB/c nude mouse model was established to assess the relationship in vivo. Our results confirmed the differential expression of STAT3/p-STAT3 not only in normal and malignant ovarian tissues but also under different matrix stiffnesses. Furthermore, we verified that STAT3 was a mechanically responsive gene both in vitro and in vivo, and the mechanical response was carried out by altering the migration-related molecules (TNFAIP1) and adhesion-related molecules (LPXN, CNN3). The novel findings suggest that STAT3, a potential therapeutic target for clinical diagnosis and treatment, is a mechanically responsive gene that responds to matrix stiffness, particularly regulation in migration and adhesion in the progression of ovarian cancer.
Correct notochord and neural tube (NT) formation is crucial to the development of the central nervous system and midline structures. Integrated biochemical and biophysical signaling controls embryonic growth and patterning; however, the underlying mechanisms remain poorly understood. Here, we took the opportunities of marked morphological changes during notochord and NT formation and identified both necessary and sufficient roles of Yap, a key mechanosensor and mechanotransducer, in biochemical signaling activation during formation of notochord and floor plate, the ventral signaling centers that pattern the dorsal-ventral axis of NT and the surrounding tissues. We showed that Yap activation by a gradient of mechanical stress and tissue stiffness in the notochord and ventral NT induces FoxA2 and Shh expression. Hedgehog signaling activation rescued NT patterning defects caused by Yap deficiency, but not notochord formation. Therefore, mechanotransduction via Yap activation acts in feedforward mechanisms to induce FoxA2 expression for notochord formation and activate Shh expression for floor plate induction by synergistically interacting with FoxA2.
Background Studies have given some pieces of evidence for the effect of total knee arthroplasty (TKA) on knee proprioception of patients with knee osteoarthritis (KOA), but their results were conflicting. This review was performed to provide an updated evidence-based meta-analysis investigating the influence of TKA on knee proprioception. Methods The electronic databases including PubMed, Google Scholar, and the Cochrane Library were accessed from their inception to March 2020. Two reviewers identified the studies that met the selection criteria for this review. Information on study type, participants, follow-up time, and outcome measures was extracted. Methodological quality was independently assessed by two reviewers using the Cochrane Handbook 5.1.0. Eleven studies with 475 participants were included in the meta-analysis. Results The I 2 index assessed the heterogeneity between studies. The results showed that the pooled standard mean difference of mean angle of error was − 0.58° (95% CI − 1 to – 0.16; P = 0.007; I 2 = 69%), and the joint position sense of KOA patients was better after TKA surgery than that before surgery. Pooled standard mean difference of displacement of center of pressure (COP) was − 0.39 (95% CI − 0.72 to − 0.06; P = 0.02; I 2 = 51%), and KOA patients had better static balance after TKA surgery than before surgery. Conclusions To conclude, no standardized comprehensive evaluation protocol presently exists though different assessment tools are available to measure proprioception. Contrasting results were found in the literature since some studies found that TKA improves proprioception in KOA patients, while others found no difference in proprioception. These differences are seen whether the proprioception was assessed by joint position sense (JPS), or it was indirectly assessed by static balance. However, the lack of sufficient data on the threshold to detect passive movement (TTDPM) and dynamic balance made it difficult to draw a conclusion about whether or not the sense of motion improved after surgery. The method for measuring and evaluating knee joint force sense is worth paying attention, which will make progress with knee proprioception on TKA patients.
PURPOSE: Electromyography (EMG) amplitude comparisons between individuals, muscles, and days need to be normalized. The gold standard, maximum voluntary isometric contraction (MVIC), is not suitable for patients with knee osteoarthritis. Standard isometric contraction (SIC) requires muscles to contract against gravity, which could provide a viable alternative. This study aimed to evaluate the within-day reliability of the SIC in patients with knee osteoarthritis and compared it with that of the conventional MVIC method. METHODS: Thirty patients with knee osteoarthritis were recruited in this study. EMG from gluteus maximus, semitendinosus, rectus femoris, vastus lateralis, tibialis anterior, gastrocnemius lateral, and soleus of the affected leg during SIC and MVIC conditions was collected three times in the same day. Intra-class correlation coefficient (ICC) with 95% confidence interval (95% CI) was calculated between three repeated measurements. RESULTS: The within-day reliability was excellent (ICC ranged 0.879 ~ 0.969) for the muscles during SIC normalization tasks (GM:0.969; SD:0.907; RF:0.879; VL:0.882; TA:0.881; GL:0.914; SL:0.965), while good to excellent (ICC ranged 0.772 ~ 0.902) during MVIC normalization tasks (GM:0.841; SD:0.805; RF:0.887; VL:0.875; TA:0.772; GL:0.902; SL:0.830). CONCLUSION: Within-day reliability of SIC normalization is excellent, and MVIC is good to excellent. SIC is more reliable, compared with MIVC, to normalize EMG in patients with knee osteoarthritis. Funding was provided by Shandong Province Young Innovative Talent Introduction and Cultivation Program (2019-183).
目的 探讨棕榈酰化修饰调节非受体酪氨酸激酶Fyn活性的分子机制.方法 利用荧光共振能量转移(fluorescence resonance energy transfer,FRET)技术实时检测细胞中的Fyn活性,并结合棕榈酰化位点缺失和共转染蛋白质酪氨酸激酶(C-terminal Src kinase,CSK)表达质粒研究其分子机制.结果 实验发现,(C3,C6)任一位点的棕榈酰化缺失能引起Fyn的高活性表达,且C6位点影响更显著.已知CSK激活后发生膜转移,FRET检测证实其对细胞中的Fyn活性有下调作用,但不能有效调控(C3,C6)棕榈酰化位点缺失的Fyn(GSS)活性.结论 本文结果初步支持了 Fyn活性受细胞内的物理空间定位分布的一种调控机制假设,即棕榈酰化缺失的Fyn(GSS)受细胞膜上CSK抑制性的调节作用被减弱,从而促进了组成性的高活性表达.
微环境中的机械力学刺激(如基质刚度、表面形貌、循环牵张),通过细胞膜上受体为巨噬细胞所感知,可沿着黏附蛋白分子链和细胞骨架向细胞核内传递,并转导为生化信号激活基因转录.机械力学刺激驱动巨噬细胞的黏附、增殖、迁移、极化等生物学行为,在疾病进展和组织再生中发挥相应作用.本文论述微环境中机械力学刺激对巨噬细胞表型和功能的影响,阐明巨噬细胞机械转导通路的相关机制,为靶向巨噬细胞的免疫调节型生物材料研发提供分子生物力学的新思路.
目的 研究不同盐离子浓度、聚乙二醇浓度和力对双根DNA扭转超螺旋结构的影响.方法 以10kbDNA为研究对象,利用磁镊的流动腔实验探究不同浓度盐离子(Na+、K+、Mg2+)、聚乙二醇(polyethylene glycol,PEG)和不同大小的力对双根DNA扭转编织体长度随圈数变化的影响.结果 双根DNA扭转结构对盐离子浓度敏感,对PEG不敏感.离子浓度越大,编织体长度随圈数变化越平缓,且Mg2+的静电屏蔽饱和浓度远低于单价阳离子.拥挤环境对DNA的影响主要为轮廓长度压缩.在4 pN以上力作用下DNA扭转结构更为稳定,2 pN以下超螺旋结构波动较大.结论 DNA的编织体结构与力学性质受所处溶液离子浓度和力的影响.研究结果有助于进一步探究染色质扭转受溶液环境影响的机制,并为拓扑异构酶在不同溶液条件下的作用效果提供参考.
外周前庭系统能够感受线性加速度(重力和头部倾斜)和旋转运动,并将其转化为神经信号,传递到中枢神经系统从而调节生理功能,其在调节躯体稳定性、眼球运动、自主神经活动、动脉压力、体温、肌肉和骨骼代谢中发挥重要的作用.重力环境可对上述功能产生影响归因于前庭系统的高可塑性.本文综述超重和微重力环境引起的前庭相关生理功能的变化,包括动脉压力、肌肉和骨骼代谢、食物摄入和体温等,旨在更好理解和研究前庭生理功能在适应特殊重力环境中的作用.
高校开展大学生军训活动旨在培养大学生的国防意识与忧患意识,进一步培养大学生的军事知识与军事技能.军训活动具有极强的育人功能,是培养与增强大学生爱国主义精神与集体主义的重要环节.在军训活动开展过程中,高强度的体能训练、耐力训练等,极容易造成学生运动损伤和运动安全问题.因此,高校在开展军训活动过程中,做好运动损伤伤害防护与急救安全教育工作十分必要.
目的 设计一种2-PSU/RR并联踝关节康复机器人,并对人体肌肉进行生物力学特性分析,研究踝关节康复机器人的康复策略.方法 采用数值离散搜索法获得机器人的实际工作空间,探究结构参数变化对机器人动平台高度的影响.通过人体生物力学仿真软件AnyBody得到肌肉力、肌肉活动度等人体生物力学响应,研究动平台高度变化对肌肉行为的影响.结果 机器人能够满足踝关节跖屈/背屈和内翻/外翻运动需求.适当增大定长杆的初始倾角和减小长度,使得踝关节康复机器人具有较低的整体高度.动平台高度依次递减10 mm,人体参与运动的肌肉力和肌肉活动度都有一定幅度下降.结论 本研究为踝关节康复提供一种新的设计方案,为踝康复机器人运动分析提供理论指导,并通过修改机构参数加快患者脚踝康复.
目的 应用线性稳定性分析方法研究延迟确定性肿瘤免疫系统的稳定性.方法 在肿瘤免疫系统中,由于免疫细胞识别肿瘤细胞到做出合适反应需要一定的时间,在此过程中考虑时间延迟,采用小延迟泰勒展开对模型进行化简,求解出平衡点.利用线性稳定性分析方法,研究平衡点的稳定性.再利用数值计算方法模拟系统及平衡点附近的轨线图,用以验证理论分析的结果.结果 在小延迟条件下,系统共有4个有意义的平衡点,分别是1个稳定焦点、1个稳定结点和2个鞍点,并且这些平衡点的类型和稳定性都不受延迟影响,数值模拟验证了理论分析的结论.结论 在小延迟条件下,系统平衡点的类型和稳定性不受延迟影响.研究结果有助于深入理解肿瘤免疫反应的动力学机制,为肿瘤的生长及治疗提供参考.
目的 提出一种新型多关节串联静脉穿刺系统,探究其穿刺过程中进针、挑针动作涉及的以力学、运动学为基础的相关控制问题,验证此系统的可行性.方法 搭建穿刺机械臂实物,结合穿刺力学模型提出进针位移控制算法.利用DH法进行正运动学解算,得到末端针尖坐标,再利用几何法进行逆运动学解算,正逆过程联系紧密.采用运动学正解-逆解-再正解方法比较挑针前后的末端坐标位置误差,最后结合实物进行实验验证与仿真.结果 经过仿真及实验,验证理论模型的准确性.利用该进针算法可以实现一针见血,为机械臂动作的控制提供理论依据.挑针前后末端位置误差可以控制在1 mm以内.机械臂在挑针过程中末端针尖几乎保持固定,故此套挑针方案可行,基本可以验证机械臂挑针动作满足精度与安全要求.结论 该静脉穿刺机械臂真实模拟穿刺过程的进针、挑针动作,能够安全、准确地实现进针穿刺和以针尖为定点的挑针动作,具有一定的临床使用价值.
目的 探讨不同牙槽窝形态上颌中切牙即刻种植即刻负重时,植入位点及轴向对种植体周围骨界面应力分布的影响.方法 参照1名健康成年人口腔锥体束计算机断层(cone beam computed tomography,CBCT)影像资料,建立偏唇型、中间型、偏腭型3种牙槽窝形态的上颌中切牙即刻种植即刻负重三维有限元模型;模拟不同植入位点(根尖位点、偏腭/唇侧位点)及轴向(牙长轴、牙槽骨长轴);对已建模型以100 N力进行不同角度(0°、30°、45°、60°、90°)的应力加载;应用ANSYS软件分析种植体周围牙槽骨的应力情况.结果 成功建立12个不同牙槽窝形态上颌中切牙即刻种植即刻负重三维有限元模型.偏唇型及中间型牙槽窝形态行即刻种植即刻负重时,沿牙槽骨长轴方向偏腭位点植入种植体更易获得良好的种植体骨界面生物力学特性;偏腭型牙槽窝形态行即刻种植即刻负重时,在偏唇位点植入,不论是沿牙长轴方向还是沿牙槽骨长轴方向植入种植体,种植体周牙槽骨所受等效应力远小于根尖位点植入.结论 不同牙槽窝形态、植入位点及轴向都会对上颌中切牙即刻种植即刻负重种植体骨界面生物力学特点产生影响.临床中,应针对不同牙槽窝形态制定不同植入轴向及植入位点的手术方案.
目的 针对材料挤出成形3D打印聚醚醚酮(polyetheretherketone,PEEK)骨替代物制造工艺存在明显各向异性的问题,以下肢股骨为例,研究不同摆放方式下3D打印PEEK股骨替代物的力学性能.方法 在有限元模型中模拟人体步态周期中5种姿态,改变正交各向异性,计算不同打印摆放方式下股骨应力与变形,并通过力学实验研究3D打印PEEK股骨的安全性与稳定性.结果 竖直摆放优于水平摆放方式,此时3D打印PEEK股骨替代物最大应力为46.56 MPa,低于PEEK材料的屈服强度但变形量大于自然股骨,满足服役过程中力学性能需求,而承载稳定性有待提高.结论 使用材料挤出成形制造承重骨时应优先采用竖直摆放的方式,3D打印技术在用于承重部位骨替代物时应谨慎考虑其各向异性对替代物服役性能的影响.
目的 分析内侧单间室膝关节骨性关节炎(knee osteoarthritis,KOA)患者接受内侧开放楔形胫骨高位截骨术(medial opening wedge high tibial osteotomy,MOWHTO)治疗后的足底压力分布情况,为患者的手术治疗和康复提供生物力学参考.方法 选取31例行单侧MOWHTO治疗后的内侧单间室KOA患者作为实验组,同时以35例同年龄健康人群作为对照组,使用Pedomedic 40?足底压力测试系统进行动态足底压力的测试.通过比较步行状态下实验组(术侧及未术侧)与对照组不同足底分区的峰值压强(Pmax)、压力时间积分(force-time integral,FTI)和接触面积(contact area,CA),评估内侧单间室KOA患者MOWHTO术后的足底压力变化.结果 与未术侧和对照组相比,术侧第1跖骨区(MH1)CA和FTI偏高(P＜0.05),第4跖骨区(MH4)CA偏小(P＜0.001),第5跖骨区(MH5)Pmax和FTI偏小(P＜0.05),中足部外侧区(MF-L)CA偏小(P＜0.001),后足部内侧区(RF-M)CA偏大(P＜0.05).未术侧与对照组相比,MH1、MH2的Pmax偏小(P＜0.05),MH5的CA、FTI偏大(P＜0.05),MF-L的Pmax偏大(P＜0.001),后足部外侧区(RF-L)的FTI偏大(P＜0.05).结论 内侧单间室KOA患者在MOWHTO术后和健康人相比存在足底压力残余异常.临床中需要有针对性地强化康复治疗来恢复患者正常的足底压力分布.
人体运动涉及生物力学、解剖学等多种学科,随着科技不断发展,人们对生物力学的研究也越来越重视.其中,踝关节扭伤是骨科临床常见的疾病.运动员踝关节扭伤风险更大,如不能及时治疗或者处理不当会很容易留下后遗症,导致关节不稳甚至发展为骨关节炎. 赵京涛主编的《骨科生物力学》由中国中医药出版社出版.全书共15个章节,主要探讨骨科生物力学研究的特点,以反映骨科生物力学领域的研究进展和临床应用,为后续骨科领域生物力学的研究提供参考.
