Impact loading in female runners with single and multiple bone stress injuries during fresh and exerted conditions

Background:Bone stress injuries(BSIs)are common in female runners,and recurrent BSI rates are high.Previous work suggests an association between higher impact loading during running and tibial BSI.However,it is unknown whether impact loading and fatigue-related loading changes discriminate women with a history of multiple BSIs.This study compared impact variables at the beginning of a treadmill run to exertion andthe changes in those variables with exertion among female runners with no history of BSI as well as among those with a history of single or multiple BSIs.Methods:We enrolled 45 female runners(aged 18-40 years)for this cross-sectional study:having no history of diagnosed lower extremity BSI(N-BSI,n=14);a history of 1 lower extremity BSI(1-BSI,n=16);and diagnosed by imaging,or a history of multiple(>3)lower extremity BSIs(M-BSI,n=15).Participants completed a 5-km race speed run on an instrumented treadmill while wearing an Inertial Measurement Unit.The vertical average loading rate(VALR),vertical instantaneous loading rate(VILR),vertical stiffness during impact via instrumented treadmill,and tibial shock determined as the peak po sitive tibial acceleration via Inertial Measurement Unit were measured at the beginning and the end of the run.Results:There were no differences between groups in VALR,VILR,vertical stiffness,or tibial shock in a fresh or exerted condition.However,compared to N-BSI,women with M-BSI had greater increase with exertion in VALR(-1.8%vs.6.1%,p=0.01)and VILR(1.5%vs.4.8%,p=0.03).Similarly,compared to N-BSI,vertical stiffness increased more with exertion among women with M-BSI(-0.9%vs.7.3%,p=0.006)and 1-BSI(-0.9%vs.1.8%,p=0.05).Finally,compared to N-BSI,the increase in tibial shock from fresh to exerted condition was greater among women with M-BSI(0.9%vs.5.5%,p=0.03)and 1-BSI(0.9%vs.11.2%,p=0.02).Conclusion:Women with 1-BSI or M-BSIs experience greater exertion-related increases in impact loading than women with N-BSI.These observations imply that exertion-related changes in gait biomechanics may contribute to risk of BSI.

Biomechanics associated with tibial stress fracture in runners:A systematic review and meta-analysis

Background:Tibial stress fracture(TSF)is an overuse running injury with a long recovery period.While many running studies refer to biomechanical risk factors for TSF,only a few have compared biomechanics in runners with TSF to controls.The aim of this systematic review and meta-analysis was to evaluate biomechanics in runners with TSF compared to controls.Methods:Electronic databases PubMed,Web of Science,SPORTDiscus,Scopus,Cochrane,and CINAHL were searched.Risk of bias was assessed and meta-analysis conducted for variables reported in 3 or more studies.Results:The search retrieved 359 unique records,but only the 14 that compared runners with TSF to controls were included in the review.Most studies were retrospective,2 were prospective,and most had a small sample size(5-30 per group).Many variables were not significantly different between groups.Meta-analysis of peak impact,active,and braking ground reaction forces found no significant differences between groups.Individual studies found larger tibial peak anterior tensile stress,peak posterior compressive stress,peak axial acceleration,peak rearfoot eversion,and hip adduction in the TSF group.Conclusion:Meta-analysis indicated that discrete ground reaction force variables were not statistically significantly different in runners with TSF compared to controls.In individual included studies,many biomechanical variables were not statistically significantly different between groups.However,many were reported by only a single study,and sample sizes were small.We encourage additional studies with larger sample sizes of runners with TSF and controls and adequate statistical power to confirm or refute these findings.

Effects of Panax notoginseng saponins on apoptosis induced by hydrogen peroxide in cultured rabbit bone marrow stromal cells via altering the oxidative stress level and down-regulating caspase-3

Objective： To investigate the effects of Panax notoginseng saponins （PNS） on hydrogen peroxide （H2O2）-induced apoptosis in cultured rabbit bone marrow stromal cells （BMSCs）. Methods： The effects of different concentrations of PNS on proliferation and early osteoblast differentiation of BMSCs were determined by the MTT assay and an alkaline phosphatase （ALP） assay. An optimal effective concentration of PNS was determined and used in subsequent experiments. The cultured BMSCs were divided into three groups： untreated control, H2O2 treated, and PNS pretreatment of H2O2 treated. The oxidative stress level was assessed by superoxide dismutase （SOD） and malondialdehyde （MDA） assays. Flow cytometry was used to determine BMSC apoptosis by staining with annexinV-FITC/propidium iodide （PI）. The activity of caspase-3 enzyme was measured by spectrofluorometry. Results： PNS （0.1g/L） significantly increased both BMSC proliferation rate and ALP activity, while it decreased the indicators of oxidative stress, caspase-3 activity, and the apoptosis rate of BMSCs induced by H2O2.. Conclusion： PNS, acting as a biological antioxidant, had a protective effect on H2O2-induced apoptosis in cultured rabbit BMSCs by decreasing oxidative stress and down-regulating caspase-3.

Bone morphogenetic protein-4 and transforming growth factor-beta1 mechanisms in acute valvular response to supra-physiologic hemodynamic stresses

AIM:To explore ex vivo the role of bone morphogenetic protein-4(BMP-4) and transforming growth factorbeta1(TGF-β1) in acute valvular response to fluid shear stress(FSS) abnormalities.METHODS:Porcine valve leaflets were subjected ex vivo to physiologic FSS,supra-physiologic FSS magnitude at normal frequency and supra-physiologic FSS frequency at normal magnitude for 48 h in a double-sided cone-and-plate bioreactor filled with standard culture medium. The role of BMP-4 and TGF-β1 in the valvular response was investigated by promoting or inhibiting the downstream action of those cytokines via culture medium supplementation with BMP-4 or the BMP antagonist noggin,and TGF-β1 or the TGF-β1 inhibitor SB-431542,respectively. Fresh porcine leaflets were used as controls. Each experimental group consisted of six leaflet samples. Immunostaining and immunoblotting were performed to assess endothelial activation in terms of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expressions,paracrine signaling in terms of BMP-4 and TGF-β1 expressions and extracellular matrix(ECM) remodeling in terms of cathepsin L,cathepsin S,metalloproteinases(MMP)-2 and MMP-9 expressions. Immunostained images were quantified by normalizing the intensities of positively stained regions by the number of cells in each image while immunoblots were quantified by densitometry. R E S U LT S :Regardless of the culture medium,physiologic FSS maintained valvular homeostasis. Tissue exposure to supra-physiologic FSS magnitude in standard medium stimulated paracrine signaling(TGF-β1:467% ± 22% vs 100% ± 6% in freshcontrols,BMP-4:258% ± 22% vs 100% ± 4% in fresh controls; P < 0.05) and ECM degradation(MMP-2:941% ± 90% vs 100% ± 19% in fresh controls,MMP-9:1219% ± 190% vs 100% ± 16% in fresh controls,cathepsin L:1187% ± 175% vs 100% ± 12% in fresh controls,cathepsin S:603% ± 88% vs 100% ± 13% in fresh controls; P < 0.05),while BMP-4 supplementation also promoted fibrosa activation and TGF-β1 inhibition reduced MMP-9 expression to the native tissue level(MMP-9:308% ± 153% with TGF-β1 inhibition vs 100% ± 16% in fresh control; P > 0.05). Supra-physiologic FSS frequency had no effect on endothelial activation and paracrine signaling regardless of the culture medium but TGF-β1 silencing attenuated FSS-induced ECM degradation via MMP-9 downregulation(MMP-9:302% ± 182% vs 100% ± 42% in fresh controls; P > 0.05).CONCLUSION:Valvular tissue is sensitive to FSS abnormalities. The TGF-β1 inhibitor SB-431542 is a potential candidate molecule for attenuating the effects of FSS abnormalities on valvular remodeling.

From Sméagol to Gollum: Mechanical Stress and Bone Remodelling

This imaginary transformation from Sméagol to Gollum is a dramatization of the illusive repercussions of mechanical stress affecting bone. This paper presents the main ideas of mechanical stress and bone remodelling from a novel’s perspective. The object of this study is to provide evidence for new ways to explore bone’s functional adaptation to mechanical stress made through the copious interpretation and integration of new and existing literature. It tackles the underlying biology of bone cells and how they detect and react to strain stimuli. The different types of mechanical demands in daily activities are sifted through and any misconceptions found fallible in literature are refined. A personal experience of a stress fracture is reviewed to parallel the implications that lead to the incident with the findings on the link between mechanical stress and bone remodelling. Some factors regarding age, gender and ethnicity and the interplay with mechanical stress influencing bone remodelling are considered. Brief overviews of three new medical novelties in bone healing are outlined, hoping that these interventions of proper medical techniques can be a change for the better: one from Gollum to Sméagol rather than vice versa.

Age- and direction-related adaptations of lumbar vertebral trabecular bone with respect to apparent stiffness and tissue level stress distribution

The objective of this study was to study the age-related adaptation of lumbar vertebral trabecular bone at the apparent level, as well as the tissue level in three orthogonal directions. Ninety trabecular specimens were obtained from six normal L4 vertebral bodies of six male cadavers in two age groups, three aged 62 years and three aged 69 years, and were scanned using a high-resolution micro-computed tomography （micro-CT） system, then converted to micro- finite element models to do micro-finite element analyses. The relationship between apparent stiffness and bone volume fraction, and the tissue level yon Mises stress distribution for each trabecular specimen when compressed separately in the longitudinal direction, medial-lateral and anterior-posterior directions （transverse directions） were derived and compared between two age groups. The results showed that at the apparent level, trabecular bones from 69-year group had stiffer bone structure relative to their volume fractions in all three directions, and in both age groups, changes in bone volume fraction could explain more variations in apparent stiffness in the longitudinal direction than the transverse directions; at the tissue level, aging had little effect on the tissue von Mises stress distributions for the compressions in all the three directions. The novelty of the present study was that it provided quantitative assessments on the age and direction- related adaptation of Chinese male lumbar vertebral trabecular bone from two different levels： stiffness at the apparent level and stress distribution at the tissue level. It may help to understand the failure mechanisms and fracture risks of vertebral body associated with aging and direction for the prevention of fracture risks in elder individuals.

姜黄素抑制NF-κB信号通路缓解氧化应激对成骨分化的损害发挥抗骨质疏松作用

目的 探讨姜黄素抑制氧化应激对成骨分化损害的机制及以剂量依赖的方式发挥抗骨质疏松的作用。方法 采用细胞氧化应激模型,加入不同浓度的姜黄素,测定骨形成指标,并检测参与的潜在信号通路。同时,用姜黄素处理小鼠去卵巢(ovariectomized, OVX)骨质疏松动物模型来证实其抗骨质疏松的作用。结果 体外实验发现,低浓度姜黄素(1~10μmol·L^(-1))促进成骨细胞增殖,提高骨形成碱性磷酸酶(alkaline phosphatase, ALP)活性,逆转氧化应激导致的成骨钙沉积下降,降低了核因子kappa-B配体的受体激动剂(RANKL)和白介素-6 (IL-6)的表达。体内实验结果显示,姜黄素(5 mg·kg^(-1))给药后部分逆转了OVX小鼠血液中丙二醛(malondialdehyde, MDA)和谷胱甘肽(glutathione, GSH)活性的比例、降低高骨代谢、增加骨密度(bone density, BMD)、改善了骨小梁的微结构,但高浓度姜黄素无氧化应激保护作用。结论 姜黄素可以减轻氧化应激的骨形成损害,NF-κB信号通路是主要参与通路,姜黄素可能是预防骨质疏松症的理想药物。

益肾补肝健骨方联合依降钙素治疗对原发性骨质疏松症的疗效及对骨代谢及氧化应激影响

目的:探讨益肾补肝健骨方联合依降钙素治疗对原发性骨质疏松症的疗效及对骨代谢及氧化应激的影响。方法:80例骨质疏松患者分为对照组与观察组,对照组肌内注射依降钙素,10 IU·次^(-1),2次·周^(-1);观察组在对照组基础上加益肾补肝健骨方治疗,两组均治疗6个月。比较两组疗效和治疗前后骨密度、骨痛情况[视觉模拟评分(visual analogue scale,VAS)]、骨代谢指标[Ⅰ型前胶原氨基端前肽(procollagen typeⅠN-terminal propeptide,PINP)及Ⅰ型胶原交联C-末端肽(type I C-terminal cross linked peptide,CTX-1)]和血清氧化应激指标[丙二醛(malondialdehyde,MDA)及高级氧化蛋白产物(advanced oxidation protein product,AOPP)]。结果:治疗后,观察组总有效率更高(97.50%vs 82.50%,P<0.05),VAS评分更低(P<0.05)。治疗后,两组PINP均上升(P<0.05),且观察组更高(P<0.05);两组CTX-1均下降(P<0.05),且观察组更低(P<0.05)。两组不良反应发生率差异不具有统计学意义(P>0.05)。结论:益肾补肝健骨方辅助西药治疗原发性骨质疏松症疗效显著,可改善患者骨代谢及氧化应激情况。

椎间隙注入不同弹性模量骨水泥对邻近上下椎体应力的影响

背景:近年来,针对腰椎间盘退变和椎间隙变窄所引起的腰部反复疼痛病症从国外引入了椎间隙注入骨水泥的治疗方法,但部分患者在治疗后出现椎体骨折的情况,原因可能是骨水泥弹性模量不佳。目的:通过腰椎三维有限元模型分析椎间隙中注入不同弹性模量骨水泥对上下椎体表面最大应力的影响。方法:招募1名脊柱正常志愿者获取CT数据,利用Mimics、Geomagic、SolidWorks、Ansys建立腰椎L_(2)-L_(5)有限元模型,随后建立L_(3)-L_(4)椎间隙注射不同剂量(1 mL与4 mL)骨水泥模型,每种剂量下赋予骨水泥4种弹性模量(1000,2000,4000,8000 MPa),在L_(2)椎体表面施加压力与弯矩,分析L_(3)椎体下表面与L_(4)椎体上表面的应力。结果与结论:①在骨水泥注入量相同的情况下,随着骨水泥弹性模量的增大,L_(3)椎体下表面与L_(4)椎体上表面的应力增加,其中弹性模量1000 MPa骨水泥对L_(3)椎体下表面与L_(4)椎体上表面的应力影响最小,弹性模量8000 MPa骨水泥对L_(3)椎体下表面与L_(4)椎体上表面的应力影响最大,不同弹性模量骨水泥对整个腰椎活动度的影响较小;②结果说明,在满足治疗要求的情况下注入较低弹性模量的骨水泥可以降低术后骨折风险。

运动训练促进骨健康的研究进展

机械负荷导致适应性骨形成。这种现象涉及骨靶向重塑和适应性骨形成。骨重建对于修复机械负荷过程中产生的疲劳损伤是必要的,而适应性骨形成是提高骨刚度和强度的有效机制。因此,可以调节机械负荷的变化,从而最大程度上促进适应性骨形成。不习惯、动态、高冲击、多向、间歇性的运动,包括延长休息时间以恢复骨骼机械敏感性,是最容易促进适应性骨形成的因素。适应性骨形成可能有助于帮助运动人群预防应力性骨折。另外,充足的睡眠、补充维生素D和钙、高能量供应,可以最优化适应性骨形成。

Therapeutic effect of bone marrow mesenchymal stem cells on cold stress induced changes in the hippocampus of rats

The present study aims to evaluate the effect of bone marrow mesenchymal stem cells on cold stress induced neuronal changes in hippocampal CA1 region of Wistar rats. Bone marrow mes- enchymal stem cells were isolated from a 6-week-old Wistar rat. Bone marrow from adult femora and tibia was collected and mesenchymal stem cells were cultured in minimal essential medium containing 10% heat-inactivated fetal bovine serum and were sub-cultured. Passage 3 cells were analyzed by flow cytometry for positive expression of CD44 and CD90 and negative expression of CD45. Once CD44 and CD90 positive expression was achieved, the cells were cultured again to 90% confluence for later experiments. Twenty-four rats aged 8 weeks old were randomly and evenly divided into normal control, cold water swim stress （cold stress）, cold stress ＋ PBS （intra- venous infusion）, and cold stress ＋ bone marrow mesenchymal stem cells （1 x 106; intravenous infusion） groups. The total period of study was 60 days which included 1 month stress period followed by 1 month treatment. Behavioral functional test was performed during the entire study period. After treatment, rats were sacrificed for histological studies. Treatment with bone marrow mesenchymal stem cells significantly increased the number of neuronal cells in hippocampal CA 1 region. Adult bone marrow mesenchymal stem cells injected by intravenous administration show potential therapeutic effects in cognitive decline associated with stress-related lesions.

微创椎间隙注入骨水泥对上下椎体应力的影响

目的通过建立腰椎模型进行生物力学分析,研究椎间盘中注入骨水泥后对上下椎体所受最大应力的影响,降低后期患者在运动和劳动中椎体骨折的风险,为治疗腰椎疼痛及椎间隙注入骨水泥手术提供实验数据和参考。方法获取符合要求的CT数据,利用Mimics、Geomagic Wrap、SolidWorks、Ansys Workbench等软件构建实验要求的腰椎有限元模型,将构建的模型进行前屈、后伸、左弯、右弯、左旋、右旋、站立运动状态分析,比较注入在不同位置和注入不同量的骨水泥对上下椎体的应力影响和变化趋势。结果成功建立了腰椎三维有限元模型。构建的腰椎三维有限元模型在各种运动中分析的结果均在既往文献数据参考范围内,可认为模型有效,可以进行下一步的实验研究。通过分析研究发现骨水泥注入到椎间盘的左侧、中间、右侧三者之间对椎体表面的最大应力差异无统计学意义(P>0.05)。通过在椎间盘中注入1 mL、4 mL和7 mL骨水泥后分析发现随着骨水泥注入量的增加上下椎体表面所受的最大应力明显下降,差异有统计学意义(P<0.05)。结论考虑到人体的实际运动更加多样和复杂等综合因素骨水泥注入到椎间盘中间更加合理,综合过往的文献和本次的实验研究在椎间盘中注入4~7 mL(50%~100%)骨水泥能达到良好的效果,但是不建议注入到100%,骨水泥渗漏的风险过大,可为临床治疗提高参考。

机械应力下骨细胞行为变化的研究进展

机械应力刺激在维持骨骼正常形态、功能和自稳平衡方面起着重要作用。过去的研究普遍认为骨细胞是不活跃的细胞。近年来,对骨细胞的深入研究表明,骨细胞是骨骼中主要的机械应力感受细胞,在机械应力下的骨形成和骨重塑过程中起着关键作用。机械应力不仅可以减少骨细胞凋亡,还能促进其分化水平。此外,受机械应力刺激的骨细胞通过直接或间接的方式来调节成骨细胞和破骨细胞的分化水平,从而维持骨结构的强度和调节骨稳态。笔者拟对机械应力下骨细胞行为变化以及其与成骨细胞和破骨细胞偶联的分子机制进行综述,旨在为今后骨质疏松基础研究提供理论参考。

芒果苷对大鼠骨髓间充质干细胞氧化应激损伤的保护作用

背景:间充质干细胞移植治疗脊髓损伤有一定效果,但仍存在局部氧化应激环境导致移植细胞存活率低、细胞移植效率不佳等问题。目的:探究芒果苷在氧化应激状态下对骨髓间充质干细胞的保护作用。方法:取第3代大鼠骨髓间充质干细胞,按浓度梯度0,20,40,80,160μmol/L加入芒果苷孵育2 h,然后加入含400μmol/L H_(2)O_(2)的无血清L-DMEM培养基及相应浓度的芒果苷继续培养12 h及24 h,以常规培养的大鼠骨髓间充质干细胞为正常对照组。MTT法检测各组细胞存活情况,按照试剂盒操作方法检测细胞培养液中超氧化物歧化酶、丙二醛及过氧化氢酶水平。结果与结论:与正常对照组相比,H_(2)O_(2)组细胞的存活能力显著降低(P<0.01),超氧化物歧化酶、过氧化氢酶水平显著降低(P<0.01),丙二醛水平显著升高(P<0.01);与H_(2)O_(2)组相比,芒果苷组细胞的存活能力显著升高(P<0.01),超氧化物歧化酶、过氧化氢酶水平显著升高(P<0.01),丙二醛水平显著降低(P<0.01)。芒果苷在20μmol/L浓度以上表现出浓度依赖性的抗氧化应激保护活性,且在160μmol/L以下无细胞毒性。结果表明,抗氧化剂芒果苷可增加骨髓间充质干细胞的抗氧化活性,为骨髓间充质干细胞移植提供一种新的预处理策略。

补骨脂活性成分治疗骨质疏松症的相关信号通路的研究进展

骨质疏松症(OP)是一种以骨量低下、骨组织微结构损坏,导致骨脆性增加、易发生骨折为特征的全身性骨病,不仅患病率、致残率、病死率高,且后遗症多,给患者及社会带来沉重负担。随着补骨脂(Psoralea corylifolia)的化学及药理作用研究取得长足进展,从中分离出的香豆素类、黄酮类和单萜酚类等化合物,具有抗OP、抗氧化、抗炎等作用,已被广泛用于OP治疗中。本文针对补骨脂活性成分在OP脂质代谢、骨代谢和氧化应激中的调节作用机制,以及以Wnt/β-catenin、PI3K/Akt、PPAR-γ/Wnt、RANKL/RANK/MAPK、NF-κB信号通路为靶点的相关治疗策略进行综述,以期为OP的预防和治疗提供参考。

正畸微植体动态植入过程有限元数值仿真

目的 建立自攻型正畸微植体动态植入模型,研究微植体动态植入过程中周围骨应力分布情况。方法 基于CBCT数据重建口腔三维模型;利用ABAQUS软件建立微植体和种植区域骨组织的有限元模型;使用三维动态有限元方法,对微植体受40 N轴向推进力、0.5 r/s恒定转速植入骨内的过程进行仿真分析。结果 成功建立了自攻型正畸微植体动态植入过程的三维有限元模型、结果可视化展示了微植体动态植入过程;结果发现植入阶段和螺纹位置对骨应力分布影响明显且不同骨质应力状态差异明显:在植入过程中,皮质骨最大应力为167 MPa,稳定阶段最大应力为50 MPa;松质骨最大应力为30 MPa。结论 植入阶段和螺纹位置对骨应力分布影响明显;皮质骨和松质骨应力差异明显。可以利用应力特征判断骨质类型,通过种植体周围的骨应力分布情况判断颌骨是否处于合适的种植状态。

骨质对右上第一磨牙种植修复体咬合调整影响的有限元分析

背景:骨组织改建与应力加载密切相关,目前就骨质与种植修复体咬合调整关系的研究或指南较少,并且缺乏科学的证据。目的:通过有限元方法探究不同种植修复体咬合间隙在Ⅰ-Ⅳ类骨质条件下时对种植体-骨界面应力分布、应力峰值、位移的影响。方法:通过光学扫描仪扫描等比例牙齿模型后,使用Solidworks 2022构建等比例右上第一磨牙Straumann 4.8×8 mm BL RC种植体及其相关部件模型,再利用Mimics、Geomagic、Solidworks软件,依据文献ZARB和LEKHOLM提出的骨质分类、NORTON和TRISI骨质密度分类,建立Ⅰ-Ⅳ类骨质的上下颌骨模型。以0,20,40,60,80,100μm为修复体咬合间隙完成模型的装配,并且额外构建一组未进行密度比设置的均质模型作为对比。将上述模型导入Hypermesh进行网格划分后,进行有限元分析的材料赋值、边界约束以及参数设定,最后以250 N为加载力模拟上下颌受力情况,分析比较各组模型中种植体-骨界面的应力分布、应力峰值和位移情况。结果与结论:①相同荷载条件下,种植修复体应力随咬合接触点均匀分布,当咬合间隙达80μm和100μm时,Ⅰ类骨质和Ⅱ、Ⅲ、Ⅳ类骨质下的种植牙冠分别出现应力中断现象。②种植体-骨界面的位移主要集中在种植体周围的皮质骨区并沿种植体长轴向下传导至底部的松质骨区域。随着Ⅰ-Ⅳ类颌骨骨质的减弱,各组模型皮质骨区产生的位移、Von Mises应力均呈现增加趋势,且均较松质骨区大。而松质骨区Von Mises应力除自Ⅱ类骨起则呈下降趋势外,其余均与皮质骨区相类似,但当咬合间隙增大时,皮质骨及松质骨区产生的应力及位移峰值则呈现逐渐减小趋势。③在咬合间隙为0-40μm的Ⅱ-Ⅳ类骨质条件下以及60μm的Ⅳ类骨质条件时,种植体-骨组织界面应力均介于20-60 MPa之间,其余各组应力均<20 MPa。④种植体Von Mises应力主要集中于种植体颈部,在咬合间隙为20μm的Ⅱ-Ⅳ类骨质条件下,种植体应力峰值均大于咬合间隙为0μm、Ⅰ类骨质条件下的144.10 MPa。⑤在不同弹性模量的均质模型中,其应力及位移分布较非均质模型更加均匀。⑥结论:实验结果从生物力学的角度证明种植义齿修复的咬合调整应该将牙槽骨骨质纳入考虑因素,临床工作中咬合间隙应随着颌骨密度的下降而增加,单颗种植牙与对颌天然牙的咬合间隙在20-40μm是一个相对合适的咬合调整方案。但由于有限元分析法的特殊性,还有待结合临床进行进一步的深入研究。

不同骨质条件下超短种植体应用于下颌后牙区的有限元分析

背景:有研究利用三维有限元方法分析了种植体在不同皮质骨厚度中的应力情况,得出皮质骨厚度影响种植体-骨界面位移值、等效应力值及种植体各部件等效应力值的结果。目前超短种植体在不同下颌骨骨质中的临床应用还存在不确定性。目的:利用三维有限元法分析超短种植体在下颌骨不同骨质中的应力分布及骨组织的应力分布情况。方法:选取1名下颌第1磨牙缺失患者的CT影像资料,利用Mimics软件创建下颌骨第1磨牙区域的模型,根据超短种植体奥齿泰系统中5 mm×5 mm TSⅢ型号绘制出所需要的植体及上部修复体模型,使用Geomagic Studio的偏置命令获取下颌4类不同骨质的模型(Ⅰ、Ⅱ、Ⅲ、Ⅳ类),将所有模型整合并交叉组合,给予不同方向载荷,分析各类模型受力后的范氏等效应力分布。结果与结论:(1)垂直载荷时:皮质骨最大应力在Ⅰ、Ⅱ、Ⅲ类骨质中相对于Ⅳ类骨更趋向于稳定,力也从分散于种植体周围到Ⅳ类骨时逐渐集中至种植体颈部与皮质骨连接处;Ⅰ类骨中最大等效应力峰值在中央螺丝区域,Ⅱ、Ⅲ、Ⅳ类骨中最大应力峰值则统一在种植体颈部与基台连接处。(2)侧向载荷时:皮质骨最大应力随着骨质条件的减弱呈逐渐增大的趋势;Ⅰ-Ⅳ类骨质中,最大应力峰值都集中在种植体与基台连接处,Ⅰ-Ⅲ类骨中种植体本身所受应力随着骨质的减弱表现出逐渐增大的趋势,到Ⅳ类骨时应力有所减小,此规律同样适用于修复体基台以及松质骨所受应力。(3)各类骨质中侧向载荷时所受到的最大应力值比垂直向载荷更大。

女贞子活性成分防治骨质疏松症的分子机制

背景:目前,中医药已被证实在抗骨质疏松方面具有显著作用,女贞子活性成分的抗骨质疏松有效性及作用机制逐渐得到学者们的关注。目的:分析总结女贞子活性成分在体内外发挥抗骨质疏松方面的研究进展。方法:检索中国知网及PubMed数据库收录的相关文献,中文检索词为“骨质疏松症,骨髓间充质干细胞,成骨细胞,破骨细胞,女贞子,信号通路”;英文检索词为“Osteoporosis,Bone marrow mesenchymal stem cells,Osteoblast,Osteoclast,Ligustri Lucidi Fructus,Signal path”,并根据研究需要确立相应的标准,对所得文献进行筛选,最终纳入82篇文献进行综述。结果与结论:女贞子活性成分在体内外发挥抗骨质疏松作用主要涉及以下几种重要成分:①红景天苷通过抑制骨硬化蛋白(SOST)和Dickkopf相关蛋白1(Dkk1)的表达,激活了Wnt/β-catenin信号通路,该激活过程增强了去卵巢大鼠和原代成骨细胞中磷酸化低密度脂蛋白受体相关蛋白6(p-LRP6)的表达,同时降低了糖原合酶激酶3β的表达。进一步地,红景天苷促进了细胞核内β-catenin、特异性转录因子2(Runx2)和骨髓细胞瘤病毒癌基因(c-Myc)的表达,从而促进了成骨细胞的骨形成能力。红景天苷可直接作用于成骨细胞,促进骨形成,为骨质疏松症的治疗提供了新的策略。②橄榄苦苷显著提高了SD大鼠的骨密度,并通过降低终末白细胞介素6和碱性磷酸酶浓度来调节骨代谢。体外实验表明,橄榄苦苷促进了成骨细胞的增殖,并上调了骨保护素蛋白和mRNA的表达,同时抑制了核转录因子κB受体活化因子配体(receptor activator of nuclear factor-κB ligand,RANKL)蛋白和mRNA的表达。这一作用机制与调节骨保护素/RANKL系统的平衡密切相关,展现出能提高骨密度,又能通过调节骨代谢相关因子来维护骨骼健康的优势,但对Ca2+浓度无显著影响,可能限制了其在某些特定骨质疏松类型中的应用。③松果菊苷通过降低磷脂酰肌醇3-激酶(phosphatidylinositol 3 kinase,PI3K)的表达、减少蛋白激酶B(protein kinase B,Akt)的磷酸化程度和破骨特殊标记蛋白(c-Fos)的表达,有效抑制了破骨细胞中PI3K/Akt/c-Fos通路的激活。这一抑制作用降低了破骨细胞的增殖和成熟能力,从而有助于减少骨吸收,其优势能直接针对破骨细胞进行干预,为骨质疏松症的治疗提供了新的靶点,但是目前对破骨细胞的具体调控机制尚需深入研究,且其长期效果和安全性需进一步评估。④女贞子活性成分在骨质疏松方面展现出良好的治疗效果,但其作用机制复杂,涉及多个基因、蛋白和信号通路的相互作用,未来需开展大规模的临床试验以验证其有效性和安全性,同时需要进一步探索女贞子活性成分与其他药物的联合应用策略,以期获得更好的治疗效果。

基于足部有限元模型的跑鞋中底结构设计分析

为从足部生物力学角度分析跑鞋中底结构的性能,建立了3种基于有限元模拟的足部接触仿真模型,模拟和预测不同跑鞋中底结构带来的足底软组织和足骨的应力分布情况。对受试者的右脚进行薄层CT扫描,将所得Dicom格式数据导入三维重建软件Mimics 21.0和逆向工程软件Geomagic Design X中进行优化处理,得到完整清晰的足部几何模型。通过网格划分软件Hypermesh对得到的足部几何模型进行网格划分,并导入有限元软件Marc进行静态数值分析。对比分析手性结构实验结果、模拟的仿真结果结果和物理实验结果,证明了有限元模型的有效性。由提取的仿真结果可知,在手性结构中,部分足底压力从足跟转移到足弓,从而释放足跟区域的压力,为足弓提供支撑,使体重分布更均匀。验证的有限元模型可用于预测跑鞋中底结构带来的足部变形和接触压力,进一步为足部疾病的临床研究提供模型支持。