The novel magnesium-titanium hybrid cannulated screws for the treatment of vertical femoral neck fractures: Biomechanical evaluation

Multiscale metal-based nanocomposites for bone and joint disease therapies

Bone and joint diseases are debilitating conditions that can result in significant functional impairment or even permanent disability. Multiscale metal-based nanocomposites, which integrate hierarchical structures ranging from the nanoscale to the macroscale, have emerged as a promising solution to this challenge. These materials combine the unique properties of metal-based nanoparticles (MNPs), such as enzyme-like activities, stimuli responsiveness, and photothermal conversion, with advanced manufacturing techniques, such as 3D printing and biohybrid systems. The integration of MNPs within polymer or ceramic matrices offers a degree of control over the mechanical strength, antimicrobial efficacy, and the manner of drug delivery, whilst concomitantly promoting the processes of osteogenesis and chondrogenesis. This review highlights breakthroughs in stimulus-responsive MNPs (e.g., photo-, magnetically-, or pH-activated systems) for on-demand therapy and their integration with biocomposite hybrids containing cells or extracellular vesicles to mimic the native tissue microenvironment. The applications of these composites are extensive, ranging from bone defects, infections, tumors, to degenerative joint diseases. The review emphasizes the enhanced load-bearing capacity, bioactivity, and tissue integration that can be achieved through hierarchical designs. Notwithstanding the potential of these applications, significant barriers to progress persist, including challenges related to long-term biocompatibility, regulatory hurdles, and scalable manufacturing. Finally, we propose future directions, including machine learning-guided design and patient-specific biomanufacturing to accelerate clinical translation. Multiscale metal-based nanocomposites, which bridge nanoscale innovations with macroscale functionality, are a revolutionary force in the field of biomedical engineering, providing personalized regenerative solutions for bone and joint diseases.

Hydrogen activates ACOD1-itaconate pathway to ameliorate steroid-associated osteonecrosis

Steroid-associated osteonecrosis (SAON) remains a challenging clinical condition as there are few effective preventive measures. This study investigates the effects of hydrogen (H2) administrated via saturated hydrogen-rich water (HRW) in mice received high dose of glucocorticoids (for inducing SAON model). Here we find that HRW treatment significantly reduces osteocyte apoptosis, improves deteriorated trabecular architecture, increases osteoblast numbers and the bone formation, while decreases osteoclast numbers and the bone resorption. Additionally, HRW-treated mice exhibit improved serum lipid profiles, including decreased levels of low-density lipoprotein (LDL), triglycerides (TG), and total cholesterol (T-CHO), as well as reduced lipid accumulation. HRW treatment also enhances blood perfusion and increases formation of type H vessels in SAON mice. We further demonstrate that HRW shifts the polarization of macrophages from M1 to M2 phenotype and suppresses inflammatory marker TNF-α. RNA sequencing data and subsequent validation reveal that HRW upregulates ACOD1 mRNA and protein levels in bone tissues. The protective effects of HRW are mimicked by supplementation with the itaconate derivative dimethyl itaconate in a dose-dependent manner, highlighting the importance of the ACOD1-itaconate pathway in the prevention of SAON by HRW. These findings indicate that HRW ameliorates SAON by modulating the ACOD1-itaconate pathway, presenting a novel avenue for the cost-effective prevention of osteonecrosis.

Magnesium as an emerging bioactive material for orthopedic applications: bedside needs lead the way from innovation to clinical translation

With the rapid increase in population aging, the number of surgical operations in orthopedics is expected to increase. The gap between the materials applied in clinical orthopedics and materials in discovery and research is obvious due to regulatory requirements for biosafety and treatment efficacy. For the bedside needs, it is important to overcome hurdles by achieving impactful innovation and clinical translation of orthopedic materials. Magnesium (Mg), as an emerging bioactive material, is one of the vital components of the human body and mainly stored in the musculoskeletal system as either a matrix component or an intracellular element for the homeostasis of various physiological functions. However, the degradation and biomechanical performance limit the applications of Mg. This review aims to explore the current challenges and future directions of Mg for clinical translation and provide an update on biomaterials used in orthopedics, factors driving orthopedic innovation, physiology of magnesium ions (Mg2+) and its potential clinical applications. To achieve orthopedic application, modification of the performance of Mg as implantable metals and function of the degradation products of Mg in vivo are described. For the clinical needs of treating the steroid-associated osteonecrosis (SAON), Mg screws and Mg-based composite porous scaffolds (Mg/PLGA/TCP: magnesium/poly(lactic-co-glycolic acid) (PLGA)/tricalcium phosphate (TCP)) have been developed, but the challenges of Mg-based implants in load-bearing skeletal sites still exist. To utilize the beneficial biological effects of Mg degradation and overcome the weakness in mechanical stability for fracture fixation, the concept of developing Mg/titanium (Ti) hybrid orthopedic implants is reported, where the Ti component provides effective mechanical support while the inclusion of Mg component potentially optimizes the biomechanical properties of Ti component and facilitate bone healing. This review provides a reference frame for the translation of novel materials and promotes the development of innovative orthopedic biomaterials for clinical applications.

Functional morphology of trabecular system in human proximal femur: a perspective from P45 sectional plastination and 3D reconstruction finite element analysis

BACKGROUND

The trabecular architecture of proximal femur plays a crucial role in hip stability and load distribution and is often ignored in hip fracture fixation due to limited anatomical knowledge. This study analyses trabecular morphology and stress distribution, aiming to provide an anatomical foundation for optimising implant designs.

MATERIALS AND METHODS

Twenty-one formalin-fixed human pelvises (twelve male, nine female) were prepared using P45 sectional plastination. They were sliced into 3 mm sections in the coronal, sagittal, and horizontal planes and then photographed. A 3D femur model was created from computed tomographic scans and analysed for finite element analysis (FEA) using Mimics, 3-matics, and Abaqus software to simulate static and dynamic loads, visualising stress paths for compressive and tensile regions and identifying fracture-vulnerable zones.

RESULTS

Two main trabecular systems were identified: the medial and lateral systems. The medial system includes a primary vertical trabecular group extending from the femoral shaft's medial calcar to the head and two primary horizontal groups arching from the lateral shaft, greater trochanter, and femoral neck's anterolateral and posterolateral walls toward the medial side, intersecting with the primary vertical group in the head. Secondary vertical group intersects with secondary horizontal group at the neck-trochanteric junction to form the lateral system. FEA showed peak compressive stress along the vertical groups, calcar, and medial cortex, and tensile stress along the horizontal groups, greater trochanter, and lateral cortex, creating balanced support that stabilises the femoral neck and shaft.

CONCLUSION

The strength of proximal femur depends on dense cortical bone, calcar femorale, lateral and medial trabecular systems, and greater trochanter. While anterolateral and posterolateral areas of femoral neck and intertrochanteric regions are potential weak zones. Trabecular pattern follows stress paths, optimising load distribution. These insights aid in designing robotic and bionic implants that mimic natural stress patterns, reducing complications.

Degradation products of magnesium implant synergistically enhance bone regeneration: Unraveling the roles of hydrogen gas and alkaline environment

Biodegradable magnesium (Mg) implant generally provides temporary fracture fixation and facilitates bone regeneration. However, the exact effects of generated Mg ions (Mg2+), hydrogen gas (H2), and hydroxide ions (OH-) by Mg degradation on enhancing fracture healing are not fully understood. Here we investigate the in vivo degradation of Mg intramedullary nail (Mg-IMN), revealing the generation of these degradation products around the fracture site during early stages. Bulk-RNA seq indicates that H2 and alkaline pH increase periosteal cell proliferation, while Mg2+ may mainly enhance extracellular matrix formation and cell adhesion in the femur ex vivo. In vivo studies further reveal that H2, Mg2+ and alkaline pH individually generate comparable effects to the enhanced bone regeneration in the Mg-IMN group. Mechanistically, the degradation products elevate sensory calcitonin gene-related peptide (CGRP) and simultaneously suppress adrenergic factors in newly formed bone. H2 and Mg2+, instead of alkaline pH, increase CGRP synthesis and inhibit adrenergic receptors. Our findings, for the first time, elucidate that Mg2+, H2, and alkaline pH environment generated by Mg-IMN act distinctly and synergistically mediated by the skeletal interoceptive regulation to accelerate bone regeneration. These findings may advance the understanding on biological functions of Mg-IMN in fracture repair and even other bone disorders.

Importance to understand medical device regulations for accelerating clinical translation

Clinical translation of medical devices is determined by many factors and is challenging for certain countries or regions as no regulatory body is available to approve related applications. They must rely on application for regulatory bodies of other countries or regions who have independent medical device regulatory systems, while the major markets regulatory process is different. For example, considering the market size and policy orientation, mainland China may be a good option for Hong Kong research organizations. Typically, China National Medical Products Administration (NMPA) has positioned innovation as a key growth engine and implemented various mechanisms to expedite the registration, including Marketing Authorization Holder policy (MAH), as well as the setting up of the NMPA's Guangdong-Hong Kong-Macao Greater Bay Area (GBA) Branch Office, type test reform and application for securing innovation channel application. However, there are still many challenges in the transitional process for Hong Kong universities or research institutions, to set up a company in mainland and then prepare many documental files from very beginning. In the future, taking advantage of NMPA reform and seeking cooperation with the NMPA to establish an independent regulatory body in Hong Kong to be recognized by NMPA is recommended as this alone will boost innovation in life sciences and boost in Hong Kong, and have a positive impact on the commercialization of medical devices in mainland China. Such example may also be relevant for many countries or regions who are seeking medical device approval in the designated regulatory systems.

Internal fixation with biodegradable high purity magnesium screws in the treatment of ankle fracture

Background

Metal plates and screws are widely used as internal fixations in the treatment of ankle fracture. However, there are many disadvantages such as "stress shielding" effect and the need for secondary surgical removal, which potentially affected the blood supply around the fracture site. In recent years, many studies confirmed that the biodegradable high purity magnesium (Mg) screws exhibited sufficient mechanical strength with adequate degradation rate for effective bone healing, avoiding the need for implant removal operations.

Method

We conducted a prospective study on patients with ankle fractures treated at Affiliated Zhongshan Hospital of Dalian University between January 2020 and January 2021. Twenty-four patients (twelve patients for each group) with ankle fractures were treated with high purity Mg screws or conventional titanium alloy plates and screws. Hematological examinations were performed in the early postoperative period, X-ray examinations were performed in the long-term postoperative follow-up. Postoperative complications, including infection, failure of internal fixation and malunion, were recorded during the follow-up. The visual analogue scale (VAS) was used to evaluate postoperative pain perceived by the patients, and the American Orthopedic Foot and Ankle Society (AOFAS) ankle-hindfoot scoring system was used to evaluate their postoperative ankle function.

Results

All patients achieved good fracture alignment, and imaging examination showed that the biodegradable high purity Mg screws degraded gradually without breakage or displacement. None of the patients experienced infection, failure of internal fixation, malunion or other complications in both groups.

Conclusion

The results showed that biodegradable high purity Mg screws could be effectively used in the clinical treatment of ankle fractures, ensuring safety and satisfactory postoperative functional recovery.The translational potential of this article: The biodegradable high purity Mg screws could provide sufficient mechanical strength and fixation stability for ankle fracture. Our study extended the clinical application of the biodegradable high purity Mg screws for fracture.

Failure analysis and design improvement of retrieved plates from revision surgery

Background

The fracture of bone plate can cause considerable pain for the patient and increase the burden on the public finances. This study aims to explore the failure mechanism of 49 plates retrieved from revision surgery and introduce pure magnesium (Mg) block to improve the biomechanical performance of the plate via decreasing the stiffness and to stimulate the biological response of the plate potentially by the degradation of Mg block.

Methods

The morphological analysis and component analysis of the plates were conducted to determine the fracture reason of the plates combining the clinical data. According to the structural feature, the 49 retrieved plates were divided into: traditional plate (TP), asymmetrical plate (AP), reconstructive plate (RP) and central enhancement plate (CEP), and their structure features are normalized in a commercial plate, respectively. The biomechanical performance of the plates was evaluated using a validated femoral finite element model. A block of pure Mg with a thickness of 1 mm, 1.5 mm and 2 mm was also incorporated into the CEP to be assessed.

Results

The results indicated that the retrieved plates mainly failed due to fatigue fracture induced by delayed union or nonunion (44/49), and using pure titanium plates in weight-bearing areas increased the risk of fracture compared with Ti alloy plates when the delayed union or nonunion occurred. The TP demonstrated the highest compression resistance and bending resistance, while CEP had the highest rotational resistance. As the thickness of the Mg block was increased, the stress on the plate in compression decreased, but the stress in rotation increased. The plate with a 1.5 mm Mg block demonstrated excellent compression resistance, bending resistance and rotational resistance.

Conclusion

Fatigue fracture resulting from the delayed union or nonunion is the primary failure reason of plates in clinic. The incorporation of Mg block into plate improves the biomechanical performance and has the potential to promote bone healing. The plate with a 1.5 mm Mg block may be suitable for use in orthopaedics.

The translational potential of this article

This study assessed the failure mechanism of retrieved bone plates and used this data to develop a novel plate incorporating a 1.5 mm block of pure Mg block at the position corresponding to the fracture line. The novel plate exhibited excellent compression resistance, bending resistance and rotational resistance due to the alleviation of stress concentrations. The Mg block has the potential to degrade over time to promote fracture healing and prevents fatigue fracture of plates.

Comparative study of a novel proximal femoral bionic nail and three conventional cephalomedullary nails for reverse obliquity intertrochanteric fractures: a finite element analysis

Purpose

Conventional cephalomedullary nails (CMNs) are commonly employed for internal fixation in the treatment of reverse obliquity intertrochanteric (ROI) fractures. However, the limited effectiveness of conventional CMNs in addressing ROI fractures results in significant implant-related complications. To address challenges associated with internal fixation, a novel Proximal Femoral Bionic Nail (PFBN) has been developed.

Methods

In this study, a finite element model was constructed using a normal femoral specimen, and biomechanical verification was conducted using the GOM non-contact optical strain measurement system. Four intramedullary fixation approaches-PFBN, Proximal Femoral Nail Antirotation InterTan nail (ITN), and Gamma nail (Gamma nail)-were employed to address three variations of ROI fractures (AO/OTA 31-A3). The biomechanical stability of the implant models was evaluated through the calculation of the von Mises stress contact pressure and displacement.

Results

Compared to conventional CMNs, the PFBN group demonstrated a 9.36%-59.32% reduction in the maximum VMS at the implant. The A3.3 ROI fracture (75% bone density) was the most unstable type of fracture. In comparison to conventional CMNs, PFBN demonstrated more stable data, including VMS values (implant: 506.33 MPa, proximal fracture fragment: 34.41 MPa), contact pressure (13.28 MPa), and displacement (17.59 mm).

Conclusion

Compared to the PFNA, ITN, and GN, the PFBN exhibits improvements in stress concentration, stress conduction, and overall model stability in ROI fractures. The double triangle structure aligns better with the tissue structure and biomechanical properties of the proximal femur. Consequently, the PFBN has significant potential as a new fixation strategy for the clinical treatment of ROI fractures.

Zinc based biodegradable metals for bone repair and regeneration: Bioactivity and molecular mechanisms

Bone fractures and critical-size bone defects are significant public health issues, and clinical treatment outcomes are closely related to the intrinsic properties of the utilized implant materials. Zinc (Zn)-based biodegradable metals (BMs) have emerged as promising bioactive materials because of their exceptional biocompatibility, appropriate mechanical properties, and controllable biodegradation. This review summarizes the state of the art in terms of Zn-based metals for bone repair and regeneration, focusing on bridging the gap between biological mechanism and required bioactivity. The molecular mechanism underlying the release of Zn ions from Zn-based BMs in the improvement of bone repair and regeneration is elucidated. By integrating clinical considerations and the specific bioactivity required for implant materials, this review summarizes the current research status of Zn-based internal fixation materials for promoting fracture healing, Zn-based scaffolds for regenerating critical-size bone defects, and Zn-based barrier membranes for reconstituting alveolar bone defects. Considering the significant progress made in the research on Zn-based BMs for potential clinical applications, the challenges and promising research directions are proposed and discussed.