Design and Mechanics Simulation of Bionic Lubrication System of Artificial Joints

We propose a new structure for artificial joints with a joint capsule which is designed to overcome the drawback of current prostheses that omit many functions of the lubricant and the joint capsule. The new structure is composed of three components： lubricant, artificial joint and artificial joint capsule. The lubricant sealed in the capsule can not only reduce the wear of the artificial joint but also prevents the wear particles leaking into the body. So unexpected reactions between the wear particles and body can be avoided completely. A three-dimensional （3-D） finite element analysis （FEA） model was created for a bionic knee joint with capsule. The stresses and their distribution in the artificial capsule were simulated with different thickness, loadings, and flexion angles. The results show that the maximum stress occurs in the area between the artificial joint and the capsule. The effects of capsule thickness and the angles of flexion on stress are discussed in detail.

Meta-analysis of new intervention measures for preventing side effects of artificial joint replacement

BACKGROUND Intertrochanteric fracture of the femur occurs mostly among older people,and seriously affects daily life and quality of life.At present,physical intervention,drug treatment,routine intervention and rehabilitation training are widely used for prevention of side effects,but it is still inconclusive which intervention has the best effect.AIM To compare the effects of new intervention measures for preventing side effects of artificial joint replacement.METHODS We searched the Chinese and English literatures for comparative studies on the prevention of side effects of new interventions for artificial joint replacement from July 2013 to June 2023 in China HowNet,PubMed,Wanfang,Weipu and other databases.Study quality was evaluated by improved Jadad scoring standard,and the effects of different interventions on preventing different complications were analyzed by meta-analysis of evidence-based medicine with Review Manager 5.0 software.RESULTS Ten articles,including 869 cases,were finally included.The preventive effects of different interventions on the side effects of artificial joint replacement were studied,and valid data were extracted.There were two articles on the preventive effects of drug intervention,four on comparison of the preventive effects of combined and single interventions,and three on the preventive effects of physical intervention,rehabilitation training and routine intervention.Meta-analysis showed that the preventive effect of rivaroxaban was significantly better than low molecular weight heparin calcium[mean difference(MD)=-0.16,95%CI:-0.28 to-0.04,P<0.05].The effect of combined intervention was significantly better than that of single intervention(MD=-0.08,95%CI:-0.16 to-0.01,P<0.001).Physical intervention was significantly better than routine intervention and rehabilitation training(MD=0.26,95%CI:0.16–0.36,P<0.001).CONCLUSION Rivaroxaban combined with rehabilitation training is preferred for preventing deep vein thrombosis after artificial joint replacement.In the prevention of pulmonary embolism,rivaroxaban drug intervention is given priority.The effect of combined intervention is better than that of single intervention.

Investigation of contact behavior on a model of the dual-mobility artificial hip joint for Asians in different inner liner thicknesses

BACKGROUND The four components that make up the current dual-mobility artificial hip joint design are the femoral head,the inner liner,the outer liner as a metal cover to prevent wear,and the acetabular cup.The acetabular cup and the outer liner were constructed of 316L stainless steel.At the same time,the inner liner was made of ultra-high-molecular-weight polyethylene(UHMWPE).As this new dual-mobility artificial hip joint has not been researched extensively,more tribological research is needed to predict wear.The thickness of the inner liner is a significant component to consider when calculating the contact pressure.AIM To make use of finite element analysis to gain a better understanding of the contact behavior in various inner liner thicknesses on a new model of a dual-mobility artificial hip joint,with the ultimate objective of determining the inner liner thickness that was most suitable for this particular type of dual-mobility artificial hip joint.METHODS In this study,the size of the femoral head was compared between two diameters(28 mm and 36 mm)and eight inner liner thicknesses ranging from 5 mm to 12 mm.Using the finite element method,the contact parameters,including the maximum contact pressure and contact area,have been evaluated in light of the Hertzian contact theory.The simulation was performed statically with dissipated energy and asymmetric behavior.The types of interaction were surface-to-surface contact and normal contact behavior.RESULTS The maximum contact pressures in the inner liner(UHMWPE)at a head diameter of 28 mm and 36 mm are between 3.7-13.5 MPa and 2.7-10.4 MPa,respectively.The maximum von Mises of the inner liner,outer liner,and acetabular cup are 2.4–11.4 MPa,15.7–44.3 MPa,and 3.7–12.6 MPa,respectively,for 28 mm head.Then the maximum von Mises stresses of the 36 mm head are 1.9-8.9 MPa for the inner liner,9.9-32.8 MPa for the outer liner,and 2.6-9.9 MPa for the acetabular cup.A head with a diameter of 28 mm should have an inner liner with a thickness of 12 mm.Whereas the head diameter was 36 mm,an inner liner thickness of 8 mm was suitable.CONCLUSION The contact pressures and von Mises stresses generated during this research can potentially be exploited in estimating the wear of dual-mobility artificial hip joints in general.Contact pressure and von Mises stress reduce with an increasing head diameter and inner liner’s thickness.Present findings would become one of the references for orthopedic surgery for choosing suitable bearing geometric parameter of hip implant.

Lifecycle of cobalt-based alloy for artificial joints:From bulk material to nanoparticles and ions due to bio-tribocorrosion

The release of debris and ions from metallic artificial joints during bio-tribocorrosion posed a severe threat to patient health.In this work,the lifecycle of a Co Cr Mo alloy was presented by investigating the subsurface microstructure transformation in-vitro.The results showed that the originally coarse grains changed to nano-grains(NGs)on the top region of the alloy,and nanoparticles(NPs)were torn off the surface,which were then blocked by the tribo-film.The agglomerated alloy NPs contained in the tribofilm transformed into debris after being removed from the alloy surface.The majority of the torn-off NPs were corroded and released ions into solution due to their high chemical activities.

The Anatomic Study on Replacement of Artificial Atlanto-odontoid Joint through Transoral Approach

In order to provide anatomical basis for transoral approach （TOA） in dealing with the ventro lesions of craniocervical junction, and the design and application of artificial atlanto-odontoid joint, microsurgical dissecting was performed on 8 fresh craniocervical specimens layer by layer through transoropharyngeal approach. The stratification of posterior pharyngeal wall, course of vertebral artery, adjacent relationship of atlas and axis and correlative anatomical parameters of replacement of artificial atlanto-odontoid joint were observed. Besides, 32 sets of atlanto-axial joint in adults＇ fresh bony specimens were measured with a digital caliper and a goniometer, including the width of bony window of anterior arch of atlas, the .width of bony window of axis vertebra, the distance between superior and inferior two atlas screw inserting points, the distance between two axis screw inserting points etc. It was found that the width of atlas and axis which could be exposed were 40.2±3.5 mm and 39.3±3.7 mm respectively. The width and height of posterior pharyngeal wall which could be exposed were 40.1±5.2 mm and 50.2±4.6 mm respectively. The distance between superior and inferior two atlas screw inserting points was 28.0±2.9 mm and 24.0±3.5 mm respectively, and the distance of bilateral axis screw inserting points was 18.0±1.2 mm. The operative exposure position through TOA ranged from inferior part of the clivus to the superior part of the C3 vertebral body. Posterior pharyngeal wall consisted of 5 layers and two interspaces： mucosa, submucosa, superficial muscular layer, anterior fascia of vertebrae, anterior muscular layer of vertebrae and posterior interspace of pharynx, anterior interspace of vertebrae. This study revealed that it had the advantages of short operative distance, good exposure and sufficient decompression in dealing with the ventro lesions from the upper cervical to the lower clivus through the TOA. The replacement of artificial atlanto-odontoid joint is suitable and feasible. The design of artificial atlanto-odontoid joint should be based on the above data.

Organizing of Virtual Enterprise for Customized Artificial Joint and Scheduling of Manufacturing Resources Based on Manufacturing Grid

In order to improve efficiency of developing customized artificial joint, a virtual enterprise is organized based on the manufacturing grid. The application-oriented framework of the virtual enterprise is created for organization of the virtual enterprise. The manufacturing system of the virtual enterprise is built up based on the exterior grid and manufacturing subsystems of member enterprises are set up based on the interior grid. Furthermore, according to characteristic matching of manufacturing resources, the scheduling flow is studied in detail and the related scheduling strategies are established. The scheduling procedure is divided into distributed scheduling stage and local scheduling stage.Based on the manufacturing grid, the organization of the virtual enterprise for customized artificial joint and the corresponding scheduling strategies can be utilized to shorten developing cycle and reduce produce cost.

人工关节国家集中带量采购的政策效果分析

目的利用中选结果数据评估人工关节集中带量采购的政策效果,以完善后续高值医用耗材集中带量采购政策。方法利用韦唐政策评估模式中的目标模式,依据人工关节集中带量采购的政策目标,构建效果评估体系,以评估人工关节集中带量采购政策效果。结果根据韦唐政策评估模式中的目标模式评估,人工关节集中带量采购平均降幅66.60%,带量比例超90.00%,价差普遍控制在2倍左右,关联中选情况少,企业分量增幅与报价及需求量的相关性符合预期,91.67%企业直接或复活中选,88.32%的分量具有延续性,至少56.87%的跨类别分量较为合理,因此基本实现了政策目标,但也出现了少数组别中选价差较大、伴随服务报价价差较大以及对医疗机构高价偏好的行为缺乏应对措施等问题。结论人工关节集中带量采购基本实现了降低耗材价格、挤压灰色空间、稳定价差、保证企业参与积极性、提高临床选择性、稳定临床供给和使用、优质产品临床替代的政策目标。建议:优化价差控制机制,减少异常中选价的出现;细化伴随服务报价规则,优化价格形成机制;避免医疗机构选择高价产品的倾向对集采产生负面影响。

Study on Tribological Properties of Irradiated Crosslinking UHMWPE Nano-Composite

Ultra High Molecular Weight Polyethylene(UHMWPE)has been widely used as a bearing material for artificial joint replacement over forty years.It is usually crosslinked by gamma rays irradiation before its implantation into human body.In this study,UHMWPE and UHMWPE/nano-hydroxyapatite(n-HA)composite were prepared by vacuum hot-pressing method.The prepared materials were irradiated by gamma rays in vacuum and molten heat treated in vacuum just after irradiation.The effect of filling n-HA with gamma irradiation on tribological properties of UHMWPE was investigated by using friction and wear experimental machine(model MM-200)under deionized water lubrication.Micro-morphology of worn surface was observed by metallographic microscope.Contact angle and hardness of the materials were also measured.The results show that contact angle and hardness are changed by filling n-HA and gamma irradiation.Friction coefficient and wear rate under deionized water lubrication are reduced by filling n-HA.While friction coefficient is increased and wear rate is reduced significantly by gamma irradiation.The worn surface of unfilled material is mainly characterized as adhesive wear and abrasive wear,and that of n-HA filled material is mainly characterized as abrasive wear.After gamma irradiation,the degrees of adhesive and abrasive wear for unfilled material and abrasive wear of n-HA filled material are significantly reduced.Unfilled and filled materials after irradiation are mainly shown as slight fatigue wear.The results indicate that UHMWPE and UHMWPE/n-HA irradiated at the dose of 150 kGy can be used as bearing materials in artificial joints for its excellent wear resistance compared to original UHMWPE.

Synthesis and Lubrication of Phosphorylcholine Derivative

The monomer of phosphorylcholine derivative, O-(5-（2-methacryloxy）-3, 3-dimethyl-3-azapentyl)-O’-（ω-hydroxy-octyl）-phosphatequaternary ammonium salt, was designed and synthesized successfully. It was characterized by the spectra ofHNMR and Mass spectra （ESI+）, and every signal was assigned. Then the lubricating characteristics of the phosphorylcholinederivative were investigated on the tribological setup of ball-oh-flat. The Ultra-High Molecular Weight Polyethylene（UHMWPE） flat was rotated against a stainless steel ball with 6 mm diameter. The load was 2.3 N, which corresponded to amaximal Hertz contact pressure of 29 MPa. Water, phosphorylcholine derivative, and Acrylic Acid （AA） solution were used aslubricants, respectively. Compared with AA, the phosphorylcholine derivative shows significant lubrication. It can be stronglyhydrated under water due to the charged segment in chemical structure. The thick water layers within the chains serves asboundary lubricants, and this is thought to be the molecular origins of lubricating behavior.

Synthesized Multi-station Tribo-test System for Bio-tribological Evaluation in Vitro

Tribological tests play an important role on the evaluation of long-term bio-tribological performances of prosthetic materials for commercial fabrication.Those tests focus on the motion simulation of a real joint in vitro with only normal loads and constant velocities,which are far from the real friction behavior of human joints characterized with variable loads and multiple directions.In order to accurately obtain the bio-tribological performances of artificial joint materials,a tribological tester with a miniature four-station tribological system is proposed with four distinctive features.Firstly,comparability and repeatability of a test are ensured by four equal stations of the tester.Secondly,cross-linked scratch between tribo-pairs of human joints can be simulated by using a gear-rack meshing mechanism to produce composite motions.With this mechanism,the friction tracks can be designed by varying reciprocating and rotating speeds.Thirdly,variable loading system is realized by using a ball-screw mechanism driven by a stepper motor,by which loads under different gaits during walking are simulated.Fourthly,dynamic friction force and normal load can be measured simultaneously.The verifications of the performances of the developed tester show that the variable frictional tracks can produce different wear debris compared with one-directional tracks,and the accuracy of loading and friction force is within ？5%.Thus the high consistency among different stations can be obtained.Practically,the proposed tester system could provide more comprehensive and accurate bio-tribological evaluations for prosthetic materials.

Magnetic suspension hip joint： an ideal design of an artificial joint

Background Artificial joints present certain problems such as osteal absorption and lysis induced by wear debris which leads to loosening of the prosthesis over a period of time. Here we propose a design of an artificial magnetic suspension joint that was prepared by integrating the medical theories of modern material science, magnetism, and medical physics.Methods According to clinical characteristic of biological and mechanical for hip joint, we designed the appearance and dimensions of magnetic suspension joint and placed neodymium-iron-boron permanent magnets in the prosthesis.As the same time, we performed mechanical and biological experiments using artificial magnetic suspension hip joints models.Results By simulated the human hip structure and the external load, we discovered the artificial magnetic suspension hip joints models had much lesser amount and size of wear debris than the ceramic/ceramic artificial hip joint prosthesis in friction wear tests. The force between the artificial joints with magnetic materials that we have calculated is feasible for application of artificial joint. The design of artificial magnetic suspension hip joints models was plausible technically and safe biologically.Conclusion Artificial magnetic suspension hip joints may effectively reduce the incidence of the loosening of prosthesis over a period of time.

Synthesis of titanium carbide coating on Ti15Mo alloy and its tribological behaviour

Ti15Mo alloy has been regarded as one of the most potential biomedical materials due to its excellent performance.However,the low hardness and poor wear resistance of titanium alloy limit the further application.Therefore,high temperature solid carburising technology was performed on the surface of Ti15Mo alloys to prepare titanium carbide(TiC)coating with graphene(G)as the carburising agent.The microstructure,mechanical properties,and tribological properties of TiC coating under different lubricants were investigated.Results showed that TiC coating was closely bonded to the titanium substrate.The maximum thickness of TiC coating treated with 1150°C was approximately 184.02μm,and the microhardness of alloys treated with 1100°C can achieve 1221.5 HV.All modified Ti15Mo alloys showed improved tribological performance compared to the original samples.The wear mechanisms of modified Ti15Mo alloys were abrasive wear and adhesive wear under the SBF lubricant,and the TiC coating was slightly peeled off.The overall friction coefficient and wear rate under 25%calf serum lubricant were lower than the SBF lubricant,and surface scratches were almost absent,and slight abrasive wear and adhesive wear occurred on the surface.

Tribological study on the surface modification of metal-on-polymer bioimplants

The tribological performance of artificial joints is regarded as the main factor of the lifespan of implanted prostheses. The relationship between surface roughness and coefficient of friction (COF) under dry and lubricated conditions is studied. Results show that under dry test, friction coefficient is not reduced all the time with a decrease in surface roughness. On the contrary, a threshold of roughness value is observed, and frictional force increases again below this value. This critical value lies between 40 and 100 nm in Sa (roughness). This phenomenon is due to the transfer of friction mechanisms from abrasion to adhesion. Under wet test, COF always decreases with reduction in surface roughness. This result is mainly attributed to the existence of a thin layer of lubricant film that prevents the intimate contact of two articulating surfaces, thus greatly alleviating adhesion friction. Furthermore, surface texturing technology is successful in improving the corresponding tribological performance by decreasing friction force and mitigating surface deterioration. The even-distribution mode of texturing patterns is most suitable for artificial joints. By obtaining the optimal surface roughness and applying texturing technology, the tribological performance of polymer-based bioimplants can be greatly enhanced.

Tribological and electrochemical studies on biomimetic synovial fluids

In this study, tribological and electrochemical performances of the new biomimetic synovial fluids were studied according to different composition concentrations, including hyaluronic acid, albumin and alendronic acid sodium. By using Taguchi method, the composition contents of the biomimetic synovial fluids were designed. Items such as friction coefficient, mean scar diameter and viscosity were investigated via a four-ball tribo-tester, viscosity meter and optical microscope. Polarization studies were carried out to analyze the electrochemical behaviour of the fluids. Results showed that hyaluronic acid dominates the viscosity of the fluids. High albumin concentration will reduce friction, while increasing wear rate due to the electro-chemical effect. Alendronic acid sodium is found to reduce the biocorrosion of CoCrMo as well as provide better lubricating. In conclusion, biomimetic synovial fluids partially recover the functions of natural synovial fluids and provide good lubricating property.

RCC Arch Dam Structure on the Taxi River and Water Storage Measure During Construction

The new structure of roller compacted concrete (RCC) arch dams is presented for extremely cold and earthquake prone areas. The influence of construction plans and improved materials on the stresses in the Taxi River dam is also given. Earlier impoundment of water is shown to not only benefit the engineering design but also improve the stresses during construction in winter. Low cement content in the concrete and artificial short joints improved the monolithic structure and the transmitted forces. The concrete plug installed in the first cooled part of the arch dam provides excellent force transmission in the arch, which increases the monolith of the earlier arch, reduces the increasing thermal stresses that occur later, and improves the deformation flexibility of the dam.