Long-term Implantation Research Articles

Graphene: future prospects for biomedical engineering applications

Graphene is one of the allotropic forms of Carbon. It is typically presented as a thin, almost transparent, and very lightweight sheet, despite its remarkable mechanical strength. Recent studies have demonstrated that graphene has significant potential for application in the medical industry, not only due to its mechanical resistance and lightness, which suggest its use in prosthetics and bionic limbs, but also because of its excellent electrical conductivity, indicating its potential in medical measurement equipment. Moreover, graphene's biocompatibility and resistance to corrosion make it an ideal material for long-term medical implants. It has been explored in the development of biosensors, enabling real-time monitoring of biological signals such as heart rate and brain activity. For instance, graphene-based sensors could be implanted to detect subtle electrical changes in neurons, which might be particularly useful in neuroprosthetics or for individuals with spinal cord injuries. Graphene's flexibility also paves the way for the creation of flexible electronic devices that could be worn on the skin or integrated into clothing for continuous health monitoring. These innovations could revolutionize personalized medicine by offering more accurate, accessible, and non-invasive diagnostic tools. As research continues to advance, graphene holds the promise of transforming biomedical engineering with cutting-edge applications that could improve patient care and treatment outcomes.

Mechanically adaptive and deployable intracortical probes enable long-term neural electrophysiological recordings

Flexible intracortical probes offer important opportunities for stable neural interfaces by reducing chronic immune responses, but their advances usually come with challenges of difficult implantation and limited recording span. Here, we reported a mechanically adaptive and deployable intracortical probe, which features a foldable fishbone-like structural design with branching electrodes on a temperature-responsive shape memory polymer (SMP) substrate. Leveraging the temperature-triggered soft-rigid phase transition and shape memory characteristic of SMP, this probe design enables direct insertion into brain tissue with minimal footprint in a folded configuration while automatically softening to reduce mechanical mismatches with brain tissue and deploying electrodes to a broader recording span under physiological conditions. Experimental and numerical studies on the material softening and structural folding-deploying behaviors provide insights into the design, fabrication, and operation of the intracortical probes. The chronically implanted neural probe in the rat cortex demonstrates that the proposed neural probe can reliably detect and track individual units for months with stable impedance and signal amplitude during long-term implantation. The work provides a tool for stable neural activity recording and creates engineering opportunities in basic neuroscience and clinical applications.

A Review of the Development of Titanium-Based and Magnesium-Based Metallic Glasses in the Field of Biomedical Materials.

This article reviews the research and development focus of metallic glasses in the field of biomedical applications. Metallic glasses exhibit a short-range ordered and long-range disordered glassy structure at the microscopic level, devoid of structural defects such as dislocations and grain boundaries. Therefore, they possess advantages such as high strength, toughness, and corrosion resistance, combining characteristics of both metals and glasses. This novel alloy system has found applications in the field of biomedical materials due to its excellent comprehensive performance. This review discusses the applications of Ti-based bulk metallic glasses in load-bearing implants such as bone plates and screws for long-term implantation. On the other hand, Mg-based metallic glasses, owing to their degradability, are primarily used in degradable bone nails, plates, and vascular stents. However, metallic glasses as biomaterials still face certain challenges. The Young's modulus value of Ti-based metallic glasses is higher than that of human bones, leading to stress-shielding effects. Meanwhile, Mg-based metallic glasses degrade too quickly, resulting in the premature loss of mechanical properties and the formation of numerous bubbles, which hinder tissue healing. To address these issues, we propose the following development directions: (1) Introducing porous structures into titanium-based metallic glasses is an important research direction for reducing Young's modulus; (2) To enhance the bioactivity of implant material surfaces, the surface modification of titanium-based metallic glasses is essential. (3) Developing antibacterial coatings and incorporating antibacterial metal elements into the alloys is essential to maintain the long-term effective antibacterial properties of metallic biomaterials. (4) Corrosion resistance must be further improved through the preparation of composite materials, while ensuring biocompatibility and safety, to achieve controllable degradation rates and degradation modes.

Non-invasive temporal interference brain stimulation reduces preference on morphine-induced conditioned place preference in rats

Long-term use of opioid drugs such as morphine can induce addiction in the central nervous system through dysregulation of the reward system of the brain. Deep brain stimulation (DBS) is a non-pharmacological technique capable of attenuating behavioral responses associated with opioid drug consumption and possesses the capability to selectively activate and target localized brain regions with a high spatial resolution. However, long-term implantation of electrodes in brain tissue may limit the effectiveness of DBS due to changes in impedance, position, and shape of the tip of the stimulation electrode and the risk of infection of nerve tissue around the implanted electrode. The main objective of the current study is to evaluate the effect of temporal interference (TI) brain stimulation on addictive behaviors of morphine-induced conditioned place preference (CPP) in rats. TI stimulation is a non-invasive technique used transcranially to modulate neural activity within targeted brain regions. It involves applying two high-frequency currents with slightly different frequencies, resulting in interference and targeted stimulation of different brain areas with the desired spatial resolution. The results indicated that TI stimulation with the amplitude of I1=I2=0.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{I}}_{1}{ = }{\ ext{I}}_{2}{ = 0.5}$$\\end{document} mA, carrier frequency of 2 kHz, frequency difference of 25 Hz, ON–OFF stimulation frequency of 0.25 Hz, and total duration of 10 min in three consecutive days resulted in a significant reduction of morphine preference in the morphine-stimulation group in comparison with the morphine group (p < 0.001). These findings highlight the potential of TI stimulation as a modulatory intervention in mitigating the addictive properties of morphine and provide valuable insights into the therapeutic implications of this stimulation paradigm for treatment of opioid drugs in human subjects.

Wireless, battery-free, and real-time monitoring of water permeation across thin-film encapsulation

Long-term bioelectronic implants require stable, hermetic encapsulation. Water and ion ingress are challenging to quantify, especially in miniaturized microsystems and over time. We propose a wireless and battery-free flexible platform leveraging backscatter communication and magnesium (Mg)-based microsensors. Water permeation through the encapsulation induces corrosion of the Mg resistive sensor thereby shifting the oscillation frequency of the sensing circuit. Experimental in vitro and in-tissue characterization provides information on the operation of the platform and demonstrates the robustness and accuracy of this promising method, revealing its significance for in-situ real-time monitoring of implanted bioelectronics.

Marginal Bone Level Changes Evaluation of Long-term Functional Dental Implants with the Implant Disease Risk Assessment Diagram: A 2 to 6 Years Follow-up Retrospective Study.

Purpose: This study aimed to evaluate the relationship between risk profile assessments of dental implants that have been in function for at least two-year and peri-implant marginal bone loss during the follow-up period using the Implant Disease Risk Assessment Diagram. Material and Methods: A total of 70 patients and 170 implants who had been functionally loaded for at least two years and who attended follow-up sessions were included in the study. Full-mouth plaque index (PI), gingival index (GI), probing depth (PD), bleeding on probing, clinical attachment level (CAL), and peri-implant modified plaque index, modified bleeding index, PD, keratinized mucosal width (KMW), CAL and GR were recorded. According to the IDRA risk diagram, participants and dental implants were divided into low, moderate, and high-risk groups. Marginal bone level (MBL) was measured on periapical radiographs obtained at functional loading (T0) and at the last follow-up session (T1), and mesial and distal marginal bone level changes (ΔMBL) were calculated as T1-T0. Results: A statistically significant correlation was found between the periodontitis history and periodontitis susceptibility and IDRA classification at the patient-level. Full-mouth GI, PD, and BOP were found to be statistically higher in the high-risk IDRA group. No statistically significant result was found between the mesial and distal ΔMBL between the IDRA risk groups.Conclusions: In this study, IDRA risk level increased especially by periodontitis susceptibility and periodontitis history, but no significant difference was found between risk groups in terms of ΔMBL.

The impact of stent protrusion into the inferior vena cava or jailing of the contralateral iliac vein on the incidence of contralateral deep vein thrombosis following venous stenting.

Iliac vein stenting is the standard of care for patients with pelvic venous disorders secondary to symptomatic iliac vein outflow obstruction. Venous stents are often extended proximally into the inferior vena cava (IVC) which may result in partial or complete coverage of the contralateral iliac vein. The purpose of this investigation is to determine if extension of iliac vein stents into the IVC results in increased risk of contralateral deep venous thrombosis (DVT). We retrospectively reviewed prospectively collected data from 409 patients who underwent iliac vein stenting at the Center for Vascular Medicine (CVM) from 2019 to 2020. Stent type, covered territories, initial and follow-up consults, ultrasound and operative reports were reviewed to assess for incidence of post-implantation DVT. Patients were stratified into three groups: Iliac vein stents which protruded into the IVC, stents that completely covered the orifice of the contralateral iliac vein and those with no stent protrusion into the IVC. Out of 409 patients, the average age was 53.96 ± 13.40 years with 94 males and 315 females. All stents placed were Venovo stents and all iliac vein lesions were non-thrombotic stenoses. The average follow-up period was 14.35 ± 10.09 months. The most common territories stented were the IVC-LCIV-LEIV (n = , 74%) and the IVC-RCIV-REIV (n = , 26%). Stent protrusion and distance into the IVC in millimeters (mm) was the following: Partial protrusion (n = 314, 77%, 27.6 ± 19.1), jailing of the contralateral iliac vein (n = 78, 19%, 45.9 ± 18.6), no protrusion (n = 16, 4%). The overall DVT rate post-implantation was 0.49% (n = 2). No DVTs ipsilateral to the index stent were identified and both DVTs were contralateral DVTs. A hypercoaguable disorder was reported in 6 patients (1.5%). There were no significant differences in prevalence of contralateral DVT between the three groups. (p = .35). The rate of contralateral DVTs post iliac vein stenting with Nitonol based stents is extremely low. Partial or complete coverage of the contralateral iliac vein via stenting does not result in an increased incidence of contralateral DVT in the short-term. Longer follow up is needed to determine if contralateral DVTs occur after long-term implantation.

(Invited) Microwires Based on Carbon Nanotubes for Medicine and Biology

Flexible and biocompatible microwires are generally employed for biomedical implants in medicine, more specifically in neuroscience. These microwires used as electrodes need to be chemically inert and electrically conducting in order to record and stimulate the electrical activity of neurons in the nervous system. The electrodes available today are made of metals and silicon that lack the required flexibility resulting in a mechanical mismatch between soft tissues and rigid metals which induces faster biofouling and inconsistent performance for long-term implants. Biofouling triggered by inflammatory responses dramatically affects the performance of neural electrodes, resulting in decreased signal sensitivity and consistency over time. Thus, long-term clinical applications require electrically conducting flexible electrode materials with reduced dimensions and antibiofouling properties. These characteristics reduce the degree of inflammatory reactions and increase the lifetime of implanted neural electrodes. Carbon nanotubes (CNTs) are well known for their flexibility, electrical conductivity, and chemical inertness. This talk will report the fabrication of CNT fibers and subsequent coating using a biocompatible flexible polymer hydrogenated nitrile butadiene rubber (HNBR). Unlike the gold standard parylene-C coating that requires processing under vacuum, dissolved elastomer HNBR polymer can deposit uniform coating in solutions. Polymer dip-coating has been employed for uniform and continuous coating of meters-long CNT fibers of multiple diameters (26 to 66 mm) to evaluate the robustness of the approach. The polymer was able to provide uniform thickness and pinhole-free coating along the CNT fiber. Furthermore, the polymer has been shown to be biocompatible when tested with in vitro elusions and culturing neurons. The covalent functionalization of CNT microwire cross-section interfacing with the neurons using hydrophilic, anti-biofouling phosphorylcholine molecules displays reduced impedance and increased hydrophilicity. These CNT microwire assemblies are promising for the development of low-impedance neural electrodes with higher hydrophilicity and protein-fouling resistance to inhibit inflammatory responses.

(Invited) 3D Printing for Tissue Scaffolds with Tunable Mechanical Durability and Sensing Capabilities

Pelvic organ prolapse (POP) is a prevalent condition among senior women, characterized by the descent or herniation of pelvic organs into the vaginal canal. It is a widespread issue, affecting a significant portion of the elderly female population, and yet, effective medical solutions for this condition remain elusive. This can be attributed to the complex nature of POP, where multiple factors, including tissue weakening and structural changes, contribute to its development. Despite the significant impact on women's quality of life, the absence of comprehensive treatment options underscores the urgency for innovative approaches to address this pressing health concern. In this context, 3D printing emerges as a valuable rapid prototyping tool, offering unique capabilities for designing and fabricating smart sensors and actuators. Its precision and versatility enable the creation of intricate devices that can be customized to specific medical applications. Moreover, 3D printing allows for the integration of sensors directly into biomedical devices, facilitating seamless monitoring and feedback mechanisms. Leveraging this technology, the research endeavors to harness the potential of 3D printing to develop advanced thermoelectric devices that can be seamlessly embedded within POP tissue scaffolds. These innovative devices will serve a dual purpose—detecting the health status of the tissue scaffolds and assessing their mechanical durability. In the realm of embedded medical devices, self-powered sensors hold particular significance due to their wireless powering capabilities and in-situ monitoring capabilities of human health. These sensors can operate without the need for external power sources or frequent battery replacements, making them ideal for long-term implantation within the human body. By tapping into the body's own energy sources or ambient environmental factors, self-powered sensors ensure continuous data collection and transmission, enhancing the efficiency and reliability of healthcare monitoring systems. Consequently, this talk aims to demonstrate the feasibility of 3D-printed thermoelectric devices as self-powered sensors, integrated into POP tissue scaffolds. These innovative devices will play a pivotal role in monitoring the tissue scaffold's condition, ensuring its mechanical integrity, and ultimately contributing to improved healthcare outcomes for women affected by POP.

On-demand bactericidal and self-adaptive antifouling hydrogels for self-healing and lubricant coatings of catheters

Catheter-related infections are one of the most common nosocomial infections with increasing morbidity and mortality, and robust antibacterial or antifouling catheter coatings remain great challenges for long-term implantation. Herein, multifunctional hydrogel coatings were developed to provide persistent and self-adaptive antifouling and antibacterial effects with self-healing and lubricant capabilities. Polyvinyl alcohol (PVA) with β-cyclodextrin (β-CD) grafts (PVA-Cd) and 4-arm polyethylene glycol (PEG) with adamantane and quaternary ammonium compound (QAC) terminals (QA-PEG-Ad) were crosslinked through host-guest recognitions between adamantane and β-CD moieties to acquire PVEQ coatings. In response to bacterial infections, QACs exhibit reversible transformation between zwitterions (pH 7.4) and cationic lactones (pH 5.5) to generate on-demand bactericidal effect. Highly hydrophilic PEG/PVA backbones and zwitterionic QACs build a lubricate surface and decrease the friction coefficient 10 times compared with that of bare catheters. The antifouling hydrated layer significantly inhibits blood protein adsorption and platelet activation and reveals negligible hemolysis and cytotoxicity. The dynamic host-guest crosslinking achieves full self-healing of cracks in PVEQ hydrogels, and the mechanical profiles were recovered to over 90 % after rejuvenating the broken hydrogels, exhibiting a long-term stability after mechanical stretching, twisting, knotting and compression. After subcutaneous implantation and local bacterial infection, the retrieved PVEQ-coated catheters display no tissue adhesion and 3 log folds lower bacterial number than that of bare catheters. PVEQ coatings effectively prevent the repeated bacterial infections and there are few inflammatory reactions in the surrounding tissue, while substantial lymphoid infiltration and inflammatory cell aggregation occur in muscle tissues around the bare catheter. Thus, this study demonstrates a catheter coating strategy by on-demand bactericidal, self-adaptive antifouling, self-healing and lubricant hydrogels to address medical devices-related infections. Statement of significanceIt is estimated over two billion peripheral intravenous catheters are annually used in hospitals around the world, and catheter-associated infection has become a great clinical challenge with rapidly rising morbidity and mortality. Surface coating is considered a promising approach, but substantial challenges remain in the development of coatings that simultaneously satisfy both anti-fouling and antibacterial attributes. Even more, few attempts have been made to design mechanically robust coatings and reversible antibacterial or antifouling capabilities, which are critical for long-term medical implants. To address these challenges, we propose a concise strategy to develop hydrogel coatings from commercially available poly(ethylene glycol) and polyvinyl alcohol. In addition to self-healing and lubricant capabilities, the reversible conversion between zwitterionic and cationic lactones of quaternary ammonium compounds enables on-demand bactericidal and self-adaptive antifouling effects.

Enhanced bioactivity and mechanical properties of silicon-infused titanium oxide coatings formed by micro-arc oxidation on selective laser melted Ti13Nb13Zr alloy

The titanium scaffolds and surface-porous implants are manufactured by fast and cheap additive methods such as selective laser melting (SLM). The obtained irregularity and relative biological inertness of the titanium need proper surface modification. This research is aimed at forming bioactive multicomponent oxide coatings by micro-arc oxidation (MAO) at different process parameters on the selective laser-melted Ti13Zr13Nb alloy. The MAO process was carried out in a base solution containing 0.15 mol/L Ca and 0.1 mol/L GP, with different amounts of metasilicate added under two different applied voltages. Scanning electron microscopy, atomic force microscopy, X-ray electron diffraction spectroscopy, nanomechanical and nano scratch tests, water contact angle measurements, phosphate deposition observed in long-term immersion tests, and biological LDH and MTT assays were performed. The results showed that the coating microstructure, morphology, and properties were significantly dependent on process parameters. In particular, the metasilicate addition and its rising content in the electrolyte resulted in the higher development of the surface followed by better viability of osteoblasts at no necrosis, with no negative change in the other parameters, usually close to those obtained on silicon-free coatings. The obtained results prove that the addition of silicon to the electrolyte at the partial expense of calcium can be favorable for long-term titanium implants made by selective laser melting.

Development of a hub-and-spoke durable left ventricular assist device program in Brazil, a middle-income country

ObjectivesTo describe the experience of a left ventricular assist device (LVAD) program in a middle-income country in a hub-and-spoke model. MethodsPatients fulfilling strict inclusion and exclusion criteria were referred from different centers in Brazil for LVAD implantation through a philanthropy program financed via a Brazilian Federal Government tax exemption structure. LVAD implantation was performed in hub-and-spoke model with a single implanting center. Data was collected retrospectively using hospital records and telephone contact with other centers. Patients that received LVAD implants external to the philanthropic program, either at this or other Brazilian centers, were not included. ResultsBetween January 1st, 2013, and December 31st, 2020, 20 adult patients underwent long-term continuous flow LVAD implantation with decentralization of post-implant patient care in regional centers. Patients were referred from 11 centers from 7 states in Brazil and underwent LVAD implantation through a philanthropy program. The median age was 52.5 years and 85% were INTERMACS profile 3 patients. Two patients had Chagas cardiomyopathy. The overall survival censored for competing risks at 1 year and 2 years were 90% and 84% respectively. Three patients (15%) underwent heart transplantation in the first 2 years after LVAD implantation. Twelve patients returned to their original centers and were followed remotely. ConclusionsThis study presents a successful LVAD implantation program in a hub-and-spoke model in Brazil. Centralization of LVAD implantation with decentralization of post-implant patient care in regional centers is feasible and safe, enabling optimal allocation of resources in middle-income countries.

Dual-Layer Nanoengineered Urinary Catheters for Enhanced Antimicrobial Efficacy and Reduced Cytotoxicity.

Catheter-associated urinary tract infection (CAUTI) is the most common healthcare-associated infection; however, current therapeutic strategies remain insufficient for standard clinical application. A novel urinary catheter featuring a dual-layer nanoengineering approach using zinc (Zn) and silver nanoparticles (AgNPs) is successfully fabricated. This design targets microbial resistance, minimizes cytotoxicity, and maintains long-term efficacy. The inner AgNPs layer provides immediate antibacterial effects against the UTI pathogens, while the outer porous Zn layer controls zero-order Ag release and generates reactive oxygen species, thus enhancing long-term bactericidal performance. Enhanced antibacterial properties of Zn/AgNPs-coated catheters are observed, resulting in 99.9% of E. coli and 99.7% of S. aureus reduction, respectively. The Zn/AgNPs-coated catheter significantly suppresses biofilm with sludge formation compared to AgNP-coated and uncoated catheters (all, p<0.05). The Zn/AgNP-coated catheter in a rabbit model demonstrated a durable, effective barrier against bacterial colonization, maintaining antimicrobial properties during the catheter indwelling period with significantly reduced inflammation and epithelial disruption compared with AgNP and uncoated groups. This innovation has the potential to revolutionize the design of antimicrobial medical devices, particularly for applications requiring long-term implantation. Although further preclinical studies are required to verify its efficacy and safety, this strategy seems to be a promising approach to preventing CAUTI-related complications.

Practical techniques for safely removing long-term implanted ventricular catheters to minimize bleeding.

Removing ventricular catheters, particularly those implanted for extended periods, poses significant challenges for neurosurgeons due to potential complications such as bleeding from adhesions to the ependyma or choroid plexus. This study aimed to review various techniques for safely removing ventricular catheters, emphasizing methods that minimize the risk of hemorrhagic complications. A comprehensive narrative review focused on techniques developed and documented in the literature for safely detaching ventricular catheters adhered to brain structures. Various techniques have been identified that enhance the safety of catheter removal. Notably, the use of monopolar diathermy to coagulate and release adhesions has proven effective. Innovations such as insulated suction devices and the strategic use of flexible endoscopes have also contributed to safer removal procedures, minimizing the risk of damaging surrounding cerebral tissue and preventing catastrophic hemorrhage. The removal of ventricular catheters, especially those with long-term implantation, requires precise and cautious techniques to avoid severe complications. The study underscores the importance of adopting advanced surgical techniques and the continuous evolution of safer practices in neurosurgery. These methods not only ensure patient safety but also facilitate the handling of potentially complex and life-threatening situations during catheter removal.

Structure and Properties of Bioactive Titanium Dioxide Surface Layers Produced on NiTi Shape Memory Alloy in Low-Temperature Plasma.

The NiTi alloy, known for its shape memory and superelasticity, is increasingly used in medicine. However, its high nickel content requires enhanced biocompatibility for long-term implants. Low-temperature plasma treatments under glow-discharge conditions can improve surface properties without compromising mechanical integrity. This study explores the surface modification of a NiTi alloy by oxidizing it in low-temperature plasma. We examine the impact of process temperatures and sample preparation (mechanical grinding and polishing) on the structure of the produced titanium oxide layers. Surface properties, including topography, morphology, chemical composition, and bioactivity, were analyzed using TEM, SEM, EDS, and an optical profilometer. Bioactivity was assessed through the deposition of calcium phosphate in simulated body fluid (SBF). The low-temperature plasma oxidization produced titanium dioxide layers (29-55 nm thick) with a predominantly nanocrystalline rutile structure. Layer thickness increased with extended processing time and higher temperatures (up to 390 °C), though the relationship was not linear. Higher temperatures led to thicker layers with more precipitates and inhomogeneities. The oxidized layers showed increased bioactivity after 14 and 30 days in SBF. Low-temperature plasma oxidation produces bioactive titanium oxide layers on NiTi alloys, with a structure and properties that can be tuned through process parameters. This method could enhance the biocompatibility of NiTi alloys for medical implants.

Advancement in biomedical implant materials-a mini review.

Metal alloys like stainless steel, titanium, and cobalt-chromium alloys are preferable for bio-implants due to their exceptional strength, tribological properties, and biocompatibility. However, long-term implantation of metal alloys can lead to inflammation, swelling, and itching because of ion leaching. To address this issue, polymers are increasingly being utilized in orthopedic applications, replacing metallic components such as bone fixation plates, screws, and scaffolds, as well as minimizing metal-on-metal contact in total hip and knee joint replacements. Ceramics, known for their hardness, thermal barrier, wear, and corrosion resistance, find extensive application in electrochemical, fuel, and biomedical industries. This review delves into a variety of biocompatible materials engineered to seamlessly integrate with the body, reducing adverse reactions like inflammation, toxicity, or immune responses. Additionally, this review examines the potential of various biomaterials including metals, polymers, and ceramics for implant applications. While metallic biomaterials remain indispensable, polymers and ceramics show promise as alternative options. However, surface-modified metallic materials offer a hybrid effect, combining the strengths of different constituents. The future of biomedical implant materials lies in advanced fabrication techniques and personalized designs, facilitating tailored solutions for complex medical needs.

Effect of Additive Manufactured Gyroid Porous Structure of Hybrid Gradients on Mechanical and Failure Properties

In bone tissue engineering, good structural and forming qualities are prerequisites for the long-term implantation of scaffolds. To mitigate the stress-shielding effect between porous bone scaffolds and the human skeleton, this study proposes a method for designing non-linear gradient gyroid porous structures with radial-axial hybrid gradients that are precisely controlled by multivariate polynomial functions to simulate human bone characteristics. The influence of the volumetric energy density on the forming quality of the porous structures was evaluated by characterizing the internal strut morphology and measuring the strut width and porosity. Finite element analysis combined with experimental observations revealed that during compression, the thin struts at the top and bottom of the hybrid-gradient porous structure deformed first, and the compressive stress and shear stress were gradually transferred from the thin struts at the upper and lower ends of the structure to the thicker struts in the middle. Compared with the axial gradient, the edge struts of the hybrid-gradient porous structures can withstand higher shear and compressive stresses. Furthermore, owing to the variation in the radial gradient, compared to structures with 20 % axial porosity variation, the hybrid-gradient porous structure with 40 % radial porosity variation and 20 % axial porosity variation exhibited an 18.10 % increase in elastic modulus and a 4.29 % increase in yield strength. Additionally, its effective energy absorption was 20.39 % higher than that of the homogeneous structures. Compared to radial-gradient porous structures, the hybrid-gradient porous structure showed a lower sensitivity of the elastic modulus and yield strength to the volumetric energy density.

Analysis of Postoperative Complication and Revision Rates and Mid- to Long-Term Implant Survival in Primary Short-Stem Total Hip Arthroplasty.

Background/Objectives: Short-stem prostheses were introduced as an alternative to conventional straight-stem prostheses. Despite their benefits, including minimally invasive approaches, soft-tissue- and bone-sparing implantation, and physiological load transfer to the metaphysis, data on postoperative complication and revision rates as well as on implant survival are scarce. Methods: A retrospective analysis of 1327 patients who underwent primary total hip arthroplasty (THA) using the Metha® short stem between 2006 and 2023 was conducted. Complication and revision rates were analysed for the intraoperative, direct postoperative, and follow-up episodes. Implant survival was analysed with the endpoint of all-cause stem revision. Results: Intraoperative complications were observed in 3.77% of the cases and included 44 hairline cracks and 6 fractures. In 15 cases (30.0%), conversion to a straight-stem or revision implant was necessary. The direct postoperative complication rate was 2.44%, and 11 revision procedures were performed during inpatient stay (0.84%). Mean follow-up was 7 years (range 1-17). During follow-up, femoral component revision was performed in 60 cases. Aseptic loosening and stem subsidence accounted for a combined percentage of 80% of all indications. Implant survival rate was 95.66% after 5 years, 95.58% after 10 years, and 95.50% after 15 years. Conclusions: Our study provides a comprehensive analysis of postoperative complication and revision rates in a large sample undergoing primary short-stem THA. Postoperative complication rates were favourable, and the long-term implant survival rates were comparable to conventional straight-stem prostheses. Therefore, short-stem THA may be considered an alternative for younger patients.

Presenting dual-functional peptides on implant surface to direct in vitro osteogenesis and in vivo osteointegration

The complex biological process of osseointegration and the bio-inertness of bone implants are the major reasons for the high failure rate of long-term implants, and have also promoted the rapid development of multifunctional implant coatings in recent years. Herein, through the special design of peptides, we use layer-by-layer assembly technology to simultaneously display two peptides with different biological functions on the implant surface to address this issue. A variety of surface characterization techniques (ellipsometry, atomic force microscopy, photoelectron spectroscopy, dissipation-quartz crystal microbalance) were used to study in detail the preparation process of the dual peptide functional coating and the physical and chemical properties, such as the composition, mechanical modulus, stability, and roughness of the coating. Compared with single peptide functional coatings, dual-peptide functionalized coatings had much better performances on antioxidant, cellular adhesion in early stage, proliferation and osteogenic differentiation in long term, as well as in vivo osteogenesis and osseointegration capabilities. These findings will promote the development of multifunctional designs in bone implant coatings, as a coping strategy for the complexity of biological process during osteointegration.

Neuronal functional connectivity is impaired in a layer dependent manner near chronically implanted intracortical microelectrodes in C57BL6 wildtype mice

Objective. This study aims to reveal longitudinal changes in functional network connectivity within and across different brain structures near chronically implanted microelectrodes. While it is well established that the foreign-body response (FBR) contributes to the gradual decline of the signals recorded from brain implants over time, how the FBR affects the functional stability of neural circuits near implanted brain–computer interfaces (BCIs) remains unknown. This research aims to illuminate how the chronic FBR can alter local neural circuit function and the implications for BCI decoders. Approach. This study utilized single-shank, 16-channel,100 µm site-spacing Michigan-style microelectrodes (3 mm length, 703 µm2 site area) that span all cortical layers and the hippocampal CA1 region. Sex balanced C57BL6 wildtype mice (11–13 weeks old) received perpendicularly implanted microelectrode in left primary visual cortex. Electrophysiological recordings were performed during both spontaneous activity and visual sensory stimulation. Alterations in neuronal activity near the microelectrode were tested assessing cross-frequency synchronization of local field potential (LFP) and spike entrainment to LFP oscillatory activity throughout 16 weeks after microelectrode implantation. Main results. The study found that cortical layer 4, the input-receiving layer, maintained activity over the implantation time. However, layers 2/3 rapidly experienced severe impairment, leading to a loss of proper intralaminar connectivity in the downstream output layers 5/6. Furthermore, the impairment of interlaminar connectivity near the microelectrode was unidirectional, showing decreased connectivity from Layers 2/3 to Layers 5/6 but not the reverse direction. In the hippocampus, CA1 neurons gradually became unable to properly entrain to the surrounding LFP oscillations. Significance. This study provides a detailed characterization of network connectivity dysfunction over long-term microelectrode implantation periods. This new knowledge could contribute to the development of targeted therapeutic strategies aimed at improving the health of the tissue surrounding brain implants and potentially inform engineering of adaptive decoders as the FBR progresses. Our study’s understanding of the dynamic changes in the functional network over time opens the door to developing interventions for improving the long-term stability and performance of intracortical microelectrodes.