Novel multilayer Ti foam with cortical bone strength and cytocompatibility

Efficient Osteogenic Activity of PEEK Surfaces Achieved by Femtosecond Laser-Hydroxylation

Poly(etheretherketone) (PEEK) is regarded as an attractive orthopedic material because of its good biocompatibility and mechanical properties similar to natural bone. The efficient activation methods for the surfaces of PEEK matrix materials have become a hot research topic. In this study, a method using a femtosecond laser (FSL) followed by hydroxylation was developed to achieve efficient bioactivity. It produces microstructures, amorphous carbon, and grafted -OH groups on the PEEK surface to enhance hydrophilicity and surface energy. Both experimental and simulation results show that our modification leads to a superior ability to induce apatite deposition on the PEEK surface. The results also demonstrate that efficient grafting of C-OH through FSL-hydroxylation can effectively enhance cell proliferation and osteogenic differentiation compared to other modifications, thus improving osteogenic activity. Overall, FSL hydroxylation treatment is proved to be a simple, efficient, and environmentally friendly modification method for PEEK activation. It could expand the applications of PEEK in orthopedics, as well as promote the surface modification and structural design of other polymeric biomaterials to enhance bioactivity.

Computational Study of the Influence of α/β-Phase Ratio and Porosity on the Elastic Modulus of Ti-Based Alloy Foams

This work aims to perform a computational analysis on the influence that microstructure and porosity have on the elastic modulus of Ti-6Al-4V foams used in biomedical applications with different α/β-phase ratios. The work is divided into two analyses, first the influence that the α/β-phase ratio has and second the effects that porosity and α/β-phase ratio have on the elastic modulus. Two microstructures were analyzed: equiaxial α-phase grains + intergranular β-phase (microstructure A) and equiaxial β-phase grains + intergranular α-phase (microstructure B). The α/β-phase ratio was variated from 10 to 90% and the porosity from 29 to 56%. The simulations of the elastic modulus were carried out using finite element analysis (FEA) using ANSYS software v19.3. The results were compared with experimental data reported by our group and those found in the literature. The β-phase amount and porosity have a synergic effect on the elastic modulus, for example, when the foam has a porosity of 29 with 0% β-phase, and it has an elastic modulus of ≈55 GPa, but when the β-phase amount increases to 91%, the elastic modulus decreases as low as 38 GPa. The foams with 54% porosity have values smaller than 30 GPa for all the β-phase amounts.

Definition, measurement, and function of pore structure dimensions of bioengineered porous bone tissue materials based on additive manufacturing: A review

Bioengineered porous bone tissue materials based on additive manufacturing technology have gradually become a research hotspot in bone tissue-related bioengineering. Research on structural design, preparation and processing processes, and performance optimization has been carried out for this material, and further industrial translation and clinical applications have been implemented. However, based on previous studies, there is controversy in the academic community about characterizing the pore structure dimensions of porous materials, with problems in the definition logic and measurement method for specific parameters. In addition, there are significant differences in the specific morphological and functional concepts for the pore structure due to differences in defining the dimensional characterization parameters of the pore structure, leading to some conflicts in perceptions and discussions among researchers. To further clarify the definitions, measurements, and dimensional parameters of porous structures in bioengineered bone materials, this literature review analyzes different dimensional characterization parameters of pore structures of porous materials to provide a theoretical basis for unified definitions and the standardized use of parameters.

Multifunctional 3D-printed bioceramic scaffolds: Recent strategies for osteosarcoma treatment

Osteosarcoma is the most prevalent bone malignant tumor in children and teenagers. The bone defect, recurrence, and metastasis after surgery severely affect the life quality of patients. Clinically, bone grafts are implanted. Primary bioceramic scaffolds show a monomodal osteogenesis function. With the advances in three-dimensional printing technology and materials science, while maintaining the osteogenesis ability, scaffolds become more patient-specific and obtain additional anti-tumor ability with functional agents being loaded. Anti-tumor therapies include photothermal, magnetothermal, old and novel chemo-, gas, and photodynamic therapy. These strategies kill tumors through novel mechanisms to treat refractory osteosarcoma due to drug resistance, and some have shown the potential to reverse drug resistance and inhibit metastasis. Therefore, multifunctional three-dimensional printed bioceramic scaffolds hold excellent promise for osteosarcoma treatments. To better understand, we review the background of osteosarcoma, primary 3D-printed bioceramic scaffolds, and different therapies and have a prospect for the future.

Silkworm spinning inspired 3D printing towards high strength scaffold for bone regeneration

Inspired by the silkworm spinning process for production of tough cocoon, a gradient printing-assembly technique with silk fibroin (SF) and hydroxyapatite (HA) to achieve high strength scaffold for bone regeneration...

Highlighting the advantages and benefits of cementless total knee arthroplasty (Review)

In the field of orthopedic surgery, cemented total knee arthroplasty (TKA) is considered to be one of the gold standards. However, there are categories of patients (i.e., obese and morbidly obese patients, younger than 65 years old) among whom cemented TKA has however a high failure rate. Moreover, the frequency of using uncemented TKA is increasing due to the potential benefits of long-term biological fixation, being an innovative field that addresses a new generation orthopedic surgical treatment which is more suitable for young patients who have good bone quality (good to very good, in terms of density). The survival rates and functional results of the latest generation of cementless TKAs may be similar to functional results and survival rates of cemented prosthesis. In conclusion, this review-type article can be considered a powerful database, extremely informative, dense, and focused on the topic mentioned above, in the interest of all medical professionals and all interested individuals.

Hydrolytic Expansion Induces Corrosion Propagation for Increased Fe Biodegradation

Fe is regarded as a promising bone implant material due to inherent degradability and high mechanical strength, but its degradation rate is too slow to match the healing rate of bone. In this work, hydrolytic expansion was cleverly exploited to accelerate Fe degradation. Concretely, hydrolyzable Mg2Si was incorporated into Fe matrix through selective laser melting and readily hydrolyzed in a physiological environment, thereby exposing more surface area of Fe matrix to the solution. Moreover, the gaseous hydrolytic products of Mg2Si acted as an expanding agent and cracked the dense degradation product layers of Fe matrix, which offered rapid access for solution invasion and corrosion propagation toward the interior of Fe matrix. This resulted in the breakdown of protective degradation product layers and even the direct peeling off of Fe matrix. Consequently, the degradation rate for Fe/Mg2Si composites (0.33 mm/y) was significantly improved in comparison with that of Fe (0.12 mm/y). Meanwhile, Fe/Mg2Si composites were found to enable the growth and proliferation of MG-63 cells, showing good cytocompatibility. This study indicated that hydrolytic expansion may be an effective strategy to accelerate the degradation of Fe-based implants.

Fabrication, Morphology Analysis, and Mechanical Properties of Ti Foams Manufactured Using the Space Holder Method for Bone Substitute Materials

Porous titanium (Ti) offers several key attributes as a biomedical material. Among the known characteristics of Ti relevant to biomedical applications, the mechanical performance and effects of a pore structure on the deformation characteristics under compressive loading were examined. The space holder method was employed to generate Ti foams with target porosities of 60%, 70%, and 80%. A micro-computed to mography analysis and light and scanning electron microscopy were performed to examine the pore morphology and microstructure. The mechanical properties along with the elastic modulus and compressive strength were evaluated via uniaxial compression testing. Ti foam samples with three porosity levels displayed average elastic moduli and compressive strengths comparable with those of human cancellous and cortical bone. All the Ti foam samples had elastic moduli similar to those of cancellous bone with their open porous structures. Although the foam samples with ~60% porosity had compressive strength comparable to that of cortical bone, the samples with ~80% porosity displayed compressive strength similar to that of cancellous bone. The results indicate that Ti foam scaffolds produced using the space holder method have great potential for applications in hard tissue engineering, as their mechanical properties and pore structures are similar to those of bone.

Porous Titanium for Biomedical Applications: Evaluation of the Conventional Powder Metallurgy Frontier and Space-Holder Technique

Titanium and its alloys are reference materials in biomedical applications because of their desirable properties. However, one of the most important concerns in long-term prostheses is bone resorption as a result of the stress-shielding phenomena. Development of porous titanium for implants with a low Young’s modulus has accomplished increasing scientific and technological attention. The aim of this study is to evaluate the viability, industrial implementation and potential technology transfer of different powder-metallurgy techniques to obtain porous titanium with stiffness values similar to that exhibited by cortical bone. Porous samples of commercial pure titanium grade-4 were obtained by following both conventional powder metallurgy (PM) and space-holder technique. The conventional PM frontier (Loose-Sintering) was evaluated. Additionally, the technical feasibility of two different space holders (NH4HCO3 and NaCl) was investigated. The microstructural and mechanical properties were assessed. Furthermore, the mechanical properties of titanium porous structures with porosities of 40% were studied by Finite Element Method (FEM) and compared with the experimental results. Some important findings are: (i) the optimal parameters for processing routes used to obtain low Young’s modulus values, retaining suitable mechanical strength; (ii) better mechanical response was obtained by using NH4HCO3 as space holder; and (iii) Ti matrix hardening when the interconnected porosity was 36–45% of total porosity. Finally, the advantages and limitations of the PM techniques employed, towards an industrial implementation, were discussed.

Cementless total knee arthroplasty

As the number of younger and more active patients treated with total knee arthroplasty (TKA) continues to increase, consideration of better fixation as a means of improving implant longevity is required. Cemented TKA remains the reference standard with the largest body of evidence and the longest follow-up to support its use. However, cementless TKA, may offer the opportunity of a more bone-sparing procedure with long lasting biological fixation to the bone. We undertook a review of the literature examining advances of cementless TKA and the reported results.

Cite this article: Bone Joint J 2016;98-B:867–73.

Histological, mechanical, and radiological study of osteoformation in titanium foam implants

BACKGROUND

Titanium (Ti) is widely used for implants because of its high mechanical reliability and because it aids osteoformation. However, it also produces artifacts during radiological imaging. Further, Ti implants can sometimes cause the surrounding bone to break. Owing to recent advances, Ti can be transformed into sponge-like, porous materials having a three-dimensional network of pores; such materials are called Ti foams. These foams exhibit distinct characteristics that make them more suitable than nonporous Ti. The objective of this study was to evaluate Ti foams as implant materials.

METHODS

Implants based on Ti foams having porosities of 80% and 90% were embedded in the femurs of 11 rabbits. Implants based on 0% porosity Ti were used as controls. Five rabbits were sacrificed 4 weeks after implantation, while the remaining were sacrificed after 12 weeks. The femurs containing the Ti implants were harvested and analyzed.

RESULTS

Biomechanical analyses showed that the 80% porosity implants induced greater osteoformation. There were significant differences in the average pushout strengths of the control and 80% porosity implants after 4 weeks (p = 0.048) and 12 weeks (p = 0.001). Histopathological analyses confirmed osteoformation in the case of the 80% porosity implants. Analyses of the micro-computed tomography images of the Ti foam-based implants did not suggest the presence of artifacts.

CONCLUSIONS

The 80% porosity Ti implants did not exhibit the shortcomings associated with conventional Ti implants. In addition, they induced greater osteoformation. Finally, the Ti foams did not produce radiological artifacts.

New Developments of Ti-Based Alloys for Biomedical Applications

Ti-based alloys are finding ever-increasing applications in biomaterials due to their excellent mechanical, physical and biological performance. Nowdays, low modulus β-type Ti-based alloys are still being developed. Meanwhile, porous Ti-based alloys are being developed as an alternative orthopedic implant material, as they can provide good biological fixation through bone tissue ingrowth into the porous network. This paper focuses on recent developments of biomedical Ti-based alloys. It can be divided into four main sections. The first section focuses on the fundamental requirements titanium biomaterial should fulfill and its market and application prospects. This section is followed by discussing basic phases, alloying elements and mechanical properties of low modulus β-type Ti-based alloys. Thermal treatment, grain size, texture and properties in Ti-based alloys and their limitations are dicussed in the third section. Finally, the fourth section reviews the influence of microstructural configurations on mechanical properties of porous Ti-based alloys and all known methods for fabricating porous Ti-based alloys. This section also reviews prospects and challenges of porous Ti-based alloys, emphasizing their current status, future opportunities and obstacles for expanded applications. Overall, efforts have been made to reveal the latest scenario of bulk and porous Ti-based materials for biomedical applications.