Biomechanical Implants Research Articles

Fabrication and characterization of magnesium implants coated with magnetic nanoparticles-wollastonite-hydroxyapatite for medical and sports injury applications: Finite element analysis

Recently, wollastonite nanoceramics were considered a suitable choice for the orthopedic applications in terms of the presence of silicon, and calcium ions. Using the nanoceramics for the coatings of orthopedic application was increased to facilitate the possibility of stabilization and integration with the host tissue and the regeneration of bone tissues. Using the ceramic coatings was extensively improved due to their biological properties. The present investigation delves into the utilization of innovative wollastonite nanoceramics (WS) fortified with magnetite nanoparticles (MNPs) as coatings for biomechanical implants. The study focuses on evaluating the bioactivity and mechanical attributes of electrophoretic coatings while characterizing their phase and structure through the employment of X-ray diffraction (XRD) and scanning electron microscope (SEM). The coatings are also evaluated for bioactivity and biodegradation in simulated body fluid (SBF) and phosphate-buffered saline (PBS) for 21 days. Additionally, the mechanical properties of the coatings are simulated using Finite Element Analysis (FEA) to predict porosity and elastic modulus. The presence of wollastonite with silica nanoparticles in a magnesium alloy significantly enhances bone formation, as evidenced by the highest degree of apatite formation observed in the alloy containing 10% wollastonite. This particular composition resulted in a remarkable 29% increase in apatite growth. These findings highlight the potential of incorporating wollastonite with silica nanoparticles to promote and improve bone formation processes. The results indicate that the specimen coated with a 10% concentration of magnetic nanoparticles (MNPs) exhibits favorable mechanical performance and desirable biological behavior, making it suitable for use in sports biomechanics implants. The results indicate that the specimen treated with a greater concentration of MNPs demonstrates advantageous mechanical characteristics and desirable biological responses, rendering it a promising candidate for the production of sports and orthopedic prostheses.

The Dynamic Impact Response of 3D-Printed Polymeric Sandwich Structures with Lattice Cores: Numerical and Experimental Investigation.

This paper proposes a dynamic drop weight impact simulation to predict the impact response of 3D printed polymeric sandwich structures using an explicit finite element (FE) approach. The lattice cores of sandwich structures were based on two unit cells, a body-centred cubic (BCC) and an edge-centred cubic (ECC). The deformation and the peak acceleration, referred to as the g-max score, were calculated to quantify their shock absorption characteristic. For the FE results verification, a falling mass impact test was conducted. The FE results were in good agreement with experimental measurements. The results suggested that the strut diameter, strut length, number and orientation, and the apparent material stiffness of the lattice cores had a significant effect on their deformation behavior and shock absorption capability. In addition, the BCC lattice core with a thinner strut diameter and low structural height might lead to poor shock absorption capability caused by structure collapse and border effect, which could be improved by increasing its apparent material stiffness. This dynamic drop impact simulation process could be applied across numerous industries such as footwear, sporting goods, personal protective equipment, packaging, or biomechanical implants.

Fabrication and selection of surrogate knee implant bearings for experimental evaluation of embedded in-vivo sensors

Total Knee Replacement (TKR) is a common procedure that is gaining importance with the aging American population. Although TKR is common, about 20% of patients report being unhappy with their results. Previous research has pointed to misalignment and loosening as contributing factors to negative outcomes. What is lacking in the field of TKR is a sensory system that can determine the internal loads of the knee in a direct manner. Implant bearings embedded with piezoelectric transducers have already shown promise in providing accurate sensing data. To perform further experimentation, prototype implant bearings that can be accurately and efficiently produced are needed. This work investigates various fabrication processes and possible materials to provide a foundation for developing surrogate biomechanical implants, especially those with integrated smart sensors. In this study, an original knee bearing is scanned and the resulting geometries used to generate prototypes. The prototypes are fabricated using a variety of methods including CNC machining and additive manufacturing. The prototypes are then tested to determine load distribution, active sensor performance, as well as kinematic performance under loading. The results of this study show that FDM printing provides quick and affordable results but is not ideal for rigorous experimentation. SLA printed prototypes are improved in final quality with an increase in fabrication time. Lastly, CNC machined processes are more labor intensive but can provide the best material characteristics. The findings from this study aim to have an impact not only on researchers studying biomedical sensing, but on the field of biomechanical implants.

3D printing of bone scaffolds with hybrid biomaterials

In this research, a novel hybrid material bone implant manufacturing through the integration of two materials using additive manufacturing (AM) technology is proposed. Biomimetic application can manufacture high strength biomechanical implants with optimised geometry and mass. The combination of polymers allows a significant leap in the development and production of a great diversity of components and applications of biomaterials. A novel hybrid scaffold with a poly lactic acid (PLA) matrix reinforced with carbohydrate particles (cHA) is analysed using digital surface software in the mass proportions of 100/0, 95/5, 90/10 and 80/20 for application in tissue and regenerative engineering, seeking a higher proposition strength of PLA. Filaments are used to fabricate scaffolds by 3D printing, using the fused deposition method. The frameworks are submitted to bioactivity tests, surface roughness evaluation, apparent porosity and mechanical analysis. Analysis of the microstructure of the composite particle evaluates the 3D surface luminance structure and the profile structure. Cross-sectional views of the specimens are extracted and analysed, and the surface roughness, waviness profile, and Gaussian filter of the structures are observed. In summary the structures are checked and analysed by SEM and EDS where possible, to observe the bioactive behaviour of the materials. The relationship between cHA content and roughness is shown to be proportional. The mechanical properties are shown to be affected by the reduced interaction between the PLA matrix and the cHA particles.

Application of a Hybrid Additive Manufacturing Methodology to Produce a Metal/Polymer Customized Dental Implant

In this paper an integrated methodology for implants personalized manufacturing is presented. This methodology materializes the hybrid material implants manufacturing through the integration of two or more advanced Additive Manufacturing (AM) technologies. Furthermore, high strength biomechanical implants with optimized geometry and mass can be manufactured by biomimetic concepts application. The combination of polymers and ceramics or polymers and metal materials (or metal alloys) allows a significant leap in the development and production of a great diversity of components and applications. The combination of advanced additive manufacturing processes, e.g. the Selective Laser Melting (SLM) or Selective Laser Sintering (SLS) and the StereoLithography (SL), make possible the production of parts with almost unlimited geometric freedom and custom multimaterial. The manufacturing flexibility and the processing capacity of the different combinations of materials - metal/polymer - obtained from hybrid additive manufacturing systems - SLM/SL - are demonstrated here by the manufacture of a dental bridge implant.

A 5 nW Quasi-Linear CMOS Hot-Electron Injector for Self-Powered Monitoring of Biomechanical Strain Variations

Piezoelectricity-driven hot-electron injectors (p-HEI) are used for self-powered monitoring of mechanical activity in biomechanical implants and structures. Previously reported p-HEI devices operate by harvesting energy from a piezoelectric transducer to generate current and voltage references which are then used for initiating and controlling the process of hot-electron injection. As a result, the minimum energy required to activate the device is limited by the power requirements of the reference circuits. In this paper we present a p-HEI device that operates by directly exploiting the self-limiting capability of an energy transducer when driving the process of hot-electron injection in a pMOS floating-gate transistor. As a result, the p-HEI device can activate itself at input power levels less than 5 nW. Using a prototype fabricated in a 0.5-μm bulk CMOS process we validate the functionality of the proposed injector and show that for a fixed input power, its dynamics is quasi-linear with respect to time. The paper also presents measurement results using a cadaver phantom where the fabricated p-HEI device has been integrated with a piezoelectric transducer and is used for self-powered monitoring of mechanical activity.

A comparison of the masticatory function between two different types of implant supported prostheses and complete denture for fully edentulous patients

For over 3 decades and since the preliminary studies on osseointegration, dental implants have been used extensively for the rehabilitation of completely and partially edentulous patients. Dental treatment with implants appears to provide many benefits for the edentulous patient as well as a significant oral function improvement and increased patient satisfaction. Fewer complaints, increased satisfaction, and higher ratings with regard to masticatory comfort and ability compared to conventional denture wearer have been all reported. Improvement attributed to the dental implant in an objective function appears to depend on the type of implant support for the denture. The implant supported denture can be divided by type of prosthesis (fixed or removable) or material for the teeth (porcelain or resin). The early form of implant prosthesis for edentulous patients was fixed dental prostheses referred by Zarb, which consisted of attached denture teeth with heatpolymerized acrylic resin to a cast metal substructure. More recently, metal ceramic fixed partial dentures are more frequently used. The latter type of prosthesis needs 8 implants because it is restored as a separated unit compared to the former splinted type with 5 to 6 implants. It is reported that the number and positioning of implants have an influence on force transfer and subsequent stress distribution around implants. The increase in number improves the biomechanical implants behavior, especially when subjected to bending forces. Distribution and magnitude of occlusal forces on implants carrying fixed prostheses was investigated while supported by 5 6 and 3 4 implants. Higher forces were observed with a decreasing number of implants. It is also reported that the type of prosthesis can affect implant loading mode. Loading of the extension parts of the prostheses, commonly used in the former type of prosthesis, caused a hinging effect. This in turn, induced considerable compressive forces on the implants closest to the location of load application and lower compressive or tensile forces on other implants. Regardless of its design, an implant-prosthesis complex transmits occlusal forces to the peri-implant bone. Therefore, the force absorption quotient of the prosthesis material has been a topic of research interest. Skalak envisaged that the use of acrylic resin teeth would be useful for shock protection on implants and recommended the use of acrylic resin as the material of choice for the occlusal surfaces of implant prostheses. The resiliency of resin was suggested as a safeguard against the negative effects of impact forces of the bone-implant interface. The literature, however, is inconclusive on its effect on shock absorption. In fact acrylic resins are burdened with technical and subjective disadvantages. For example, due to their low wear resistances, premature contacts often occur after several months of prosthesis delivery. Conversely, gold and porcelain surfaces are not considered to provide adequate

Comparison of Dog and Pig Models for Testing Substernal Cardiac Compression Devices

Subtle anatomic differences between species can be a critical consideration when determining whether a given animal model is appropriate for surgical research purposes, especially when testing biomechanical implants. This study compares the effectiveness of two common animal models (dogs and pigs) in testing a balloon based cardiac compression device designed for substernal placement. Pigs were used in acute studies using an infarction model of heart failure, whereas dogs were used in chronic experiments in which heart failure was induced via rapid pacing. Systolic cardiac compression was accomplished in both species using identical balloons inflated between the sternum and right ventricle with every heartbeat. Results showed the device to be much more effective in pigs, where cardiac stroke volumes returned to normal with balloon assistance (14.7 +/- 1.9 to 37.8 +/- 9.2 mL, p < 0.005). Stroke volumes in dogs, however, remained essentially unaltered by balloon activation (28.1 +/- 14.1 to 29.6 +/- 14.7 mL, p = NS). Retrospective comparisons showed pig models to be a much closer approximation to the human anatomy because of a more similar thoracic cavity shape and heart orientation. These findings suggest that certain large animal models should not be used in research in which chest wall shape or cardiac orientation within the thoracic cavity may influence outcomes.

Method for anchoring biomechanical implants to muscle tendon and chest wall.

Reliable tissue fixation is of fundamental importance to the successful development of muscle powered motor prostheses. This report describes a series of canine implant trials used to develop stable tissue-device interface mechanisms. Muscle pumps were fitted with prototype tendon and chest wall anchoring schemes and secured to the ribs and humeral insertion of latissimus dorsi (LD) muscles. LD stimulation was initiated 1 week postimplantation and continued throughout the implant period to stress these fixation sites. Design modification and implant testing were continued until both muscle and chest wall attachment points were found to be stable. Chest wall fixation was best achieved using perforated metallic plates wired to the ribs, as opposed to bone screws or wire mesh, which were subject to degradation. Direct attachment of the native tendon by means of spiked clamping plates proved ineffective. Stable muscle attachment was ultimately achieved by replacing the humeral tendon with an artificial substitute formed from fine polyester fibers gathered into 6-8 bundles and sewn into the LD insertion. Braided into a single cord, these fibers were fixed to the device by means of spiked clamping plates. Based on these findings, we conclude that perforated anchor plates and multifibrous artificial tendons can function as effective tissue-device interface mechanisms.