基于选择性激光熔化技术的骨缺损修复用梯度多孔钛支架的研制与表征

为提高骨缺损修复的治疗效果,设计孔隙率为78.8%、70.8%、62.6%和54.4%的梯度多孔钛支架(分别表示为P1,P2,P3和P4),并通过选择性激光熔化技术进行制备。通过模拟和实验方法研究支架的成形性、显微组织、力学性能和渗透性能。模拟结果表明,4种梯度结构的最大等效应力和渗透性分别在569.1~1469.0MPa和(21.7~54.6)×10^(−9)m^(2)范围内,并且P3和P4具有更小的最大等效应力,表明P3和P4具有更高的强度。P3和P4结构支架的显微组织为α'马氏体,屈服强度和弹性模量分别为185.3~250.8MPa和6.1~9.7GPa。相比于P3结构支架,P4结构支架展现出更高的强度和与皮质骨更加匹配的弹性模量,并且其渗透性(18.6×10^(−9)m^(2))在人体骨组织渗透性范围内。因此,具有P4结构支架有望被应用于骨科植入领域。

Improving the fretting biocorrosion of Ti6Al4V alloy bone screw by decorating structure optimised TiO2 nanotubes layer

TiO2 nanotubes(NT)has been demonstrated its potential in orthopaedic applications due to its enhanced surface wettability and bio-osteointegration.However,the fretting biocorrosion is the main concern that limited its successfully application in orthopaedic application.In this study,a structure optimised thin TiO2 nanotube(SONT)layer was successfully created on Ti6Al4V bone screw,and its fretting corrosion performance was investigated and compared to the pristine Ti6Al4V bone screws and NT decorated screw in a bone-screw fretting simulation rig.The results have shown that the debonding TiO2 nanotube from the bone screw reduced significantly,as a result of structure optimisation.The SONT layer also exhibited enhanced bio-corrosion resistance compared pristine bone screw and conventionally NT modified bone screw.It is postulated that interfacial layer between TiO2 nanotube and Ti6Al4V substrate,generated during structure optimisation process,enhanced bonding of TiO2 nanotube layer to the Ti6Al4V bone screws that leading to the improvement in fretting corrosion resistance.The results highlighted the potential SONT in orthopaedic application as bone fracture fixation devices.

Design and performance evaluation of additively manufactured composite lattice structures of commercially pure Ti(CP-Ti)

Ti alloys with lattice structures are garnering more and more attention in the field of bone repair or regeneration due to their superior structural,mechanical,and biological properties.In this study,six types of composite lattice structures with different strut radius that consist of simple cubic(structure A),body-centered cubic(structure B),and edge-centered cubic(structure C)unit cells are designed.The designed structures are firstly simulated and analysed by the finite element(FE)method.Commercially pure Ti(CP-Ti)lattice structures with optimized unit cells and strut radius are then fabricated by selective laser melting(SLM),and the dimensions,microtopography,and mechanical properties are characterised.The results show that among the six types of composite lattice structures,combined BA,CA,and CB structures exhibit smaller maximum von-Mises stress,indicating that these structures have higher strength.Based on the fitting curves of stress/specific surface area versus strut radius,the optimized strut radius of BA,CA,and CB structures is 0.28,0.23,and 0.30 mm respectively.Their corresponding compressive yield strength and compressive modulus are 42.28,30.11,and 176.96 MPa,and 4.13,2.16,and 7.84 GPa,respectively.The CP-Ti with CB unit structure presents a similar strength and compressive modulus to the cortical bone,which makes it a potential candidate for subchondral bone restorations.

Characteristics of novel Ti-10Mo-xCu alloy by powder metallurgy for potential biomedical implant applications

When biomaterials are implanted in the human body,the surfaces of the implants become favorable sites for microbial adhesion and biofilm formation,causing peri-implant infection which frequently results in the failure of prosthetics and revision surgery.Ti-Mo alloy is one of the commonly used implant materials for load-bearing bone replacement,and the prevention of infection of Ti-Mo implants is therefore crucial.In this study,bacterial inhibitory copper(Cu)was added to Ti-Mo matrix to develop a novel Ti-Mo-Cu alloy with bacterial inhibitory property.The effects of Cu content on microstructure,tensile properties,cytocompatibility,and bacterial inhibitory ability of Ti-Mo-Cu alloy were systematically investigated.Results revealed that Ti-10Mo-1Cu alloy consisted ofαandβphases,while there were a few Ti2Cu intermetallic compounds existed for Ti-10Mo-3Cu and Ti-10Mo-5Cu alloys,in addition toαandβphases.The tensile strength of Ti-10Mo-xCu alloy increased with Cu content while elongation decreased.Ti-10Mo-3Cu alloy exhibited an optimal tensile strength of 1098.1 MPa and elongation of 5.2%.Cytocompatibility study indicated that none of the Ti-10Mo-xCu alloys had a negative effect on MC3T3-E1 cell proliferation.Bacterial inhibitory rates against S.aureus and E.coli increased with the increase in Cu content of Ti-10Mo-xCu alloy,within the ranges of 20-60%and 15-50%,respectively.Taken together,this study suggests that Ti-10Mo-3Cu alloy with high strength,acceptable elongation,excellent cytocompatibility,and the bacterial inhibitory property is a promising candidate for biomedical implant applications.

Growth of TiO2 Nanotube on Titanium Substrate to Enhance its Biotribological Performance and Biocorrosion Resistance

TiO2 nanotubes(NTs)have a great potential in improving the osetointegration of titanium(Ti)-based biomaterials.Much efforts have been made to evaluate the biological performance of the TiO2 nanotube in regulating protein adsorption and cells attachments.As often used in orthopaedic applications,although biotribological performance and biocorrosion are important issues in these applications,few researches have been reported on the biotribological perfonnance of NT layers.This paper reports the preparation of a structure-optimised TiO2 NT(SO-NT)material via a multi-step oxidation strategy,as well as its biotribological and biocorrosion behaviours.In this procedure,an interfacial bonding layer of approximately 120 nm=150 nm was first formed on the titanium substrate,which was then joined to the NT bottoms.The mechanical testing with respect to impact,bending,and biotribological perfbnnance have demonstrated the resultant SO-NT layer possess improved mechanical stability compared to conventional NT.The uniform hyperfine interfacial bonding layer with nano-sized grains exhibited a strong bonding to NT layer and Ti substrate.It was observed that the layer not only effectively dissipates external impacts and shear stress but also acts as a good corrosion resistance barrier to prevent the Ti substrate from corrosion.Theoretical models were proposed to analyze and predict the shear performance and corrosion-resistance mechanisms of the resultant material.The obtained results demonstrated that the SO-NT material has great potential in orthopaedic applications.

Osteochondral scaffolds for early treatment of cartilage defects in osteoarthritic joints:from bench to clinic

Osteoarthritis is a degenerative joint disease,typified by the loss in the quality of cartilage and bone at the interface of a synovial joint,resulting in pain,stiffness and reduced mobility.The current surgical treatment for advanced stages of the disease is joint replacement,where the non-surgical therapeutic options or less invasive surgical treatments are no longer effective.These are major surgical procedures which have a substantial impact on patients’quality of life and lifetime risk of requiring revision surgery.Treatments using regenerative methods such as tissue engineering methods have been established and are promising for the early treatment of cartilage degeneration in osteoarthritis joints.In this approach,3-dimensional scaffolds(with or without cells)are employed to provide support for tissue growth.However,none of the currently available tissue engineering and regenerative medicine products promotes satisfactory durable regeneration of large cartilage defects.Herein,we discuss the current regenerative treatment options for cartilage and osteochondral(cartilage and underlying subchondral bone)defects in the articulating joints.We further identify the main hurdles in osteochondral scaffold development for achieving satisfactory and durable regeneration of osteochondral tissues.The evolution of the osteochondral scaffolds–from monophasic to multiphasic constructs–is overviewed and the osteochondral scaffolds that have progressed to clinical trials are examined with respect to their clinical performances and their potential impact on the clinical practices.Development of an osteochondral scaffold which bridges the gap between small defect treatment and joint replacement is still a grand challenge.Such scaffold could be used for early treatment of cartilage and osteochondral defects at early stage of osteoarthritis and could either negate or delay the need for joint replacements.

Fretting corrosion of screws contribute to the fixation failure of the femoral neck:a case report

Fretting corrosion of metal implants has been associated with implant failure and revision surgeries.This report describes the fixation failure of a femoral neck fracture in a 61-year-old male patient due to corrosion of three cannulated screws.Radiographic evaluation at the time of primary surgery demonstrated well-positioning of the cannulated screws.The patient had no significant medical comorbidities at the time of surgery.However,screw loosening and avascular necrosis were diagnosed after 5 years.At the revision surgery,inflammatory serological markers,C-reactive protein and erythrocyte sedimentation rate showed no signs of infections,and screws were retrieved.Scanning electron microscopy observations showed that all screws were subjected to fretting corrosion which led to discolouration,pitting attack,and cracking.Thus,Fretting corrosion may have contributed to the failure of the fixation of screws.

On the mechanical aspect of additive manufactured polyether-ether-ketone scaffold for repair of large bone defects

Polyether-ether-ketone(PEEK)is widely used in producing prosthesis and have gained great attention for repair of large bone defect in recent years with the development of additive manufacturing.This is due to its excellent biocompatibility,good heat and chemical stability and similar mechanical properties which mimics natural bone.In this study,three replicates of rectilinear scaffolds were designed for compression,tension,three-point bending and torsion test with unit cell size of 0.8 mm,a pore size of 0.4 mm,strut thickness of 0.4 mm and nominal porosity of 50%.Stress-strain graphs were developed from experimental and finite element analysis models.Experimental Young’s modulus and yield strength of the scaffolds were measured from the slop of the stress-strain graph to be 395 and 19.50 MPa respectively for compression,427 and 6.96 MPa respectively for tension,257 and 25.30 MPa respectively for three-point bending and 231 and 12.83 MPa respectively for torsion test.The finite element model was found to be in good agreement with the experimental results.Ductile fracture of the struct subjected to tensile strain was the main failure mode of the PEEK scaffold,which stems from the low crystallinity of additive manufacturing PEEK.The mechanical properties of porous PEEK are close to those of cancellous bone and thus are expected to be used in additive manufacturing PEEK bone implants in the future,but the lower yield strength poses a design challenge.

Optimising soft tissue in-growth in vivo in additive layer manufactured osseointegrated transcutaneous implants

Osseointegrated transcutaneous implants could provide an alternative and improved means of attaching artificial limbs for amputees,however epithelial down growth,inflammation,and infections are common failure modalities associated with their use.To overcome these problems,a tight seal associated with the epidermal and dermal adhesion to the implant is crucial.This could be achieved with specific biomaterials(that mimic the surrounding tissue),or a tissue-specific design to enhance the proliferation and attachment of dermal fibroblasts and keratinocytes.The intraosseous transcutaneous amputation prosthesis is a new device with a pylon and a flange,which is specifically designed for optimising soft tissue attachment.Previously the flange has been fabricated using traditional machining techniques,however,the advent of additive layer manufacturing(ALM)has enabled 3-dimensional porous flanges with specific pore sizes to be used to optimise soft tissue integration and reduce failure of osseointegrated transcutaneous implants.The study aimed to investigate the effect of ALM-manufactured porous flanges on soft tissue ingrowth and attachment in an in vivo ovine model that replicates an osseointegrated percutaneous implant.At 12 and 24 weeks,epithelial downgrowth,dermal attachment and revascularisation into ALM-manufactured flanges with three different pore sizes were compared with machined controls where the pores were made using conventional drilling.The pore sizes of the ALM flanges were 700,1000 and 1250μm.We hypothesised that ALM porous flanges would reduce downgrowth,improve soft tissue integration and revascularisation compared with machined controls.The results supported our hypothesis with significantly greater soft tissue integration and revascularisation in ALM porous flanges compared with machined controls.

Additive manufacturing innovation for musculoskeletal tissue repair and regeneration:from bench to bedside

Additive manufacturing(AM)or three-dimensional(3D)printing is a technique that builds the 3D objects from a 3D digital model(either by a computer-aided design or by scanning the object)in a layer-by-layer fashion.There are seven categories of AM process as defined in the ISO/ASTM 52900:2021,1 based on their working principles.These include vat photopolymerization,powder bed fusion,material extrusion,binder jetting,directed energy deposition,material jetting,and sheet lamination.1 Over the past decades,AM technology has been exploited in many fields such as the medical,automotive,aerospace and industries.

Additive manufactured polyether-ether-ketone implants for orthopaedic applications:a narrative review

Polyether-ether-ketone(PEEK)is believed to be the next-generation biomedical material for orthopaedic implants that may replace metal materials because of its good biocompatibility,appropriate mechanical properties and radiolucency.Currently,some PEEK implants have been used successfully for many years.However,there is no customised PEEK orthopaedic implant made by additive manufacturing licensed for the market,although clinical trials have been increasingly reported.In this review article,design criteria,including geometric matching,functional restoration,strength safety,early fixation,long-term stability and manufacturing capability,are summarised,focusing on the clinical requirements.An integrated framework of design and manufacturing processes to create customised PEEK implants is presented,and several typical clinical applications such as cranioplasty patches,rib prostheses,mandibular prostheses,scapula prostheses and femoral prostheses are described.The main technical challenge faced by PEEK orthopaedic implants lies in the poor bonding with bone and soft tissue due to its biological inertness,which may be solved by adding bioactive fillers and manufacturing porous architecture.The lack of technical standards is also one of the major factors preventing additive-manufactured customised PEEK orthopaedic implants from clinical translation,and it is good to see that the abundance of standards in the field of additive-manufactured medical devices is helping them enter the clinical market.