Bioabsorbable Magnesium Research Articles

A multi-domain computational framework investigating the short- and long-term viability of bioabsorbable magnesium fixation for tibial fractures

This study presents a multi-domain computational framework to investigate the long-term performance of permanent and bioabsorbable magnesium fixation devices in orthopaedic fracture applications. The framework integrates a coupled model for bone fracture healing and remodeling, with an enhanced surface-based corrosion model to predict the performance of bioabsorbable magnesium devices. It was found that plated fracture fixation enabled fracture healing outcomes compare to non-plated models by facilitating direct fracture healing. During the fracture healing phase, it was found that the stiff titanium plate provided a better healing response compared to the less stiff bioabsorbable magnesium plates. However, in the longer-term remodeling phase, the titanium plate showed evidence of stress-shielding and inhibited bone remodeling. On the other hand, the magnesium plates showed that there was continued remodeling, which meant that the bone tissue gradually returned to the pre-fracture stress state. While the corrosion rate and pit severity heavily influenced the mechanical support provided by the corroding magnesium fixator, the results showed that fixation was only required to provide mechanical stability to the fracture region for approximately the first 30 days for successful fracture union to occur. This coupled computational framework provides a platform to investigate the role of a wide range of magnesium fixation devices and their design and optimisation in orthopaedic applications.

Influence of Noble Metals on Morphology and Topology of Structural Elements in Magnesium Alloy.

The main motivation for this study was to improve implant materials. The influence of silver and gold on the structure and mechanical properties of Mg-Nd-Zr alloy was studied. In the work, quantitative and qualitative evaluation of the structural components of magnesium alloy with noble metal additives was performed. The research methods used were investigation of the mechanical properties and observation of micro- and macrostructures. The results showed that modification of magnesium alloy with Ag and Au contributes to the formation of spherical intermetallics of smaller size groups, which become additional centers of crystallization and grind the cast structure. The best composition from additional alloying with silver and gold was determined. Their positive effect on the strength and ductility properties of the metal was established. Preclinical and clinical testing was performed and the prospects for noble metal modification of bioabsorbable magnesium alloy for implant production usage were shown.

Biodegradable PTMC-MAO composite coatings on AZ31 Mg-alloys for enhanced corrosion-resistance

Bio-absorbable magnesium (Mg) alloys exhibit significant promise for implantable medical devices, particularly in orthopedic applications. However, their limited corrosion resistance and rapid degradation rates have hindered their clinical translation. To address this long-standing challenge, here we developed a composite coating system (PTMC-MAO) for Mg-alloys, seamlessly integrating Microarc oxidation (MAO) and Poly-(Trimethylene Carbonate) (PTMC) layers. Leveraging the synergistic effects between MAO coatings, generated through micro-arc oxidation, and PTMC coatings, synthesized via gradual dropwise addition, our approach effectively controls corrosion and degradation rates of a widely applied Mg-alloy (AZ31) both in terms of kinetics and thermodynamics. Compared with the uncoated AZ31, the PTMC-MAO coatings exhibited greater positive Ecorr of −1290 mV and lower icorr of 5.3 nA· cm-2 with a significant 851-fold reduction. The coatings reached up to a distinguished protection efficiency (η) of 99.9 %, accompanying with the higher impedance |Z| of 4×105 Ω·cm2. The ΔpH change and the released Mg2+ concentration were 0.25 and 42 μg/ml, respectively, after 21 days of immersion. Both values were superior to those observed for the AZ31 substrate. These results highlight the transformational potential of PTMC-MAO composite coatings, indicating their feasibility as a new class of materials for engineering the surfaces of Mg-based degradable implants.

The usefulness of bioabsorbable magnesium implants in addition to metal plates in the treatment of complex distal radius fractures

Purpose: The aim of this study was to determine whether normal plating yields comparable outcomes to plating using additional bioabsorbable screws or wires for complex distal radial fractures.Methods: Among 80 patients with complex distal radius fractures treated between January 2018 and March 2021, 45 were studied retrospectively and divided into two groups as follows: group A (n=23) received a plate, and group B (n=22) received a plate with a bioresorbable screw or wire. Radiological studies evaluated the period of bone union, radial length, inclination, and resorption of the bioresorbable screws or wires after surgery. The Disabilities of the Arm, Shoulder, and Hand (DASH) score was examined for clinical evaluation, and complications were compared between the two groups.Results: The two groups showed similar distributions in sex, age, injury mechanism, diabetes mellitus, smoking, and mean follow-up period; however, there were no statistically significant differences in the period of bone union and maintenance of reduction (radial length, inclination, and volar tilt). The DASH score averaged 14.8 and 13.2 points in groups A and B, respectively, showing no significant difference in complications (nonunion, malunion, infection, and arthritis).Conclusion: Regardless of the use of additional bioresorbable screws or wires, reduction in distal radius fractures in both groups yielded good results. Plating with additional bioresorbable screws or wires may be a suitable fixation method to compensate for the shortcomings of metal implants in complex distal radius fractures.

Medial malleolar fixation with bioabsorbable magnesium screws; a retrospective study with a mean follow-up of 5 years

BackgroundThis retrospective study aimed to investigate the mid-term clinical and radiological results of medial malleolar fixation with bioabsorbable magnesium screws. Methods44 patients who underwent a medial malleolar fixation for either fracture or osteotomy with magnesium bioabsorbable compression screws between 2015 and 2020 were retrospectively reviewed. Medial malleolar osteotomy was used for cartilage restorative procedures of talus osteochondral lesions (TOL), and biplanar chevron osteotomy was performed in all of them. Clinical results were evaluated using the American Orthopedic Foot and Ankle Society (AOFAS) scale during the final follow-up. Bone healing, loss of reduction, gas formation, implant failure, and resorption were examined through available serial radiographs. All complications were also documented and reported. ResultsPatients were followed with a mean of 61.3 ± 20.2 months (range 27–94). The mean AOFAS score at the final clinical follow-up was 91.6 ± 10.3 points (range 52–100). The postoperative AOFAS score significantly improved in TOL cases compared to preoperative scores (p: 0.001, 46.4 ± 15.0, and 89.1 ± 11.2, respectively). The final radiographic examination showed no signs of ankle osteoarthritis in 36 patients (Grade 0) and Grade I ankle osteoarthritis in eight. Only one patient had a nonunion and was revised with titanium screws. Another patient had early screw breakage but recovered without intervention. ConclusionsThis is the first study that reports the mid-term results of Mg bioabsorbable screws in the current literature. The findings in the present study indicate that Mg bioabsorbable screw fixation might be a good alternative for medial malleolar fracture or osteotomy fixation with a high rate of union and low rate of complications. Besides, it eliminates the need for implant removal.Level of evidence: Level IV, therapeutic, retrospective case series.

Foot Surgery Using Resorbable Magnesium Screws

The use of bioabsorbable magnesium (Mg) screws is new in foot surgery. Their relative merit over conventional titanium screws has not yet been proven. This prospective case series study was conducted to compare the clinical and radiological outcomes of bioabsorbable Mg screws and titanium screws. A consecutive series of patients (n=60; 11 men and 49 women) underwent corrective hallux valgus surgery. The minimum follow-up period was 1 year. The assessment was based on a patient questionnaire, including the American Orthopedic Foot and Ankle Society(AOFAS) hallux valgus score, visual analog scale, patient's global impression of change (PGIC), and fifth metatarsus circumference (IF5C). The radiographic assessment included the intermetatarsal and hallux valgus angles, as well as time to osteotomy union and hardware failure. At 1 year, similar results were obtained radiographically. The healing of the osteotomies was significantly faster in the Mg group. Hardware failure was common in the Mg group (5/26) than in the TI group (0/34) but hardware removal was more common in the TI group (6/34) versus the MG group (0/26). IF5C increased by 8 ± 2 mm in the Mg group. The AOFAS and PGIC scores at 6 months were similar. Validated foot scores and radiographic analysis indicated that there was no detectable difference between the groups. The fast achievement of osteotomy union compensates for a high rate of hardware failure, resulting in patient satisfaction and avoiding reoperation for hardware removal.

Effect of surface modification on interfacial behavior in bioabsorbable magnesium wire reinforced poly-lactic acid polymer composites

The mechanical behavior, corrosion mechanisms, and cytocompatibility at the interface of magnesium wires reinforced poly-lactic acid polymer composites were studied by in vitro degradation study of 180 days. Surface modification of Mg wires by plasma-electrolytic oxidation improved the interface shear strength from 10.9 MPa to 26.3 MPa which decreased to 8 MPa and 13.6 MPa in Mg/PLA and PEO-Mg/PLA composites, respectively, after 42 days of in vitro degradation. Cross-sections of the composite showed good cytocompatibility, although the cells tended to migrate towards the PLA regions and avoided the surface of the Mg wires. Corrosion of Mg wires (without surface modification) was very fast in composite while corrosion of surface-modified Mg wires was significantly reduced, hydrogen gas was suppressed and only 3% mass loss of Mg wires was found after 180 days. Finally, the corrosion mechanisms at interface were discussed for both composites.

Predicting localised corrosion and mechanical performance of a PEO surface modified rare earth magnesium alloy for implant use through in-silico modelling

In this study, the influence of a plasma electrolytic oxidation (PEO) surface treatment on a medical-grade WE43-based magnesium alloy is examined through an experimental and computational framework that considers the effects of localised corrosion features and mechanical properties throughout the corrosion process. First, a comprehensive in-vitro immersion study was performed on WE43-based tensile specimens with and without PEO surface modification, which included fully automated spatial reconstruction of the phenomenological features of corrosion through micro-CT scanning, followed by uniaxial tensile testing. Then the experimental data of both unmodified and PEO-modified groups were used to calibrate parameters of a finite element-based surface corrosion model. In-vitro, it was found that the WE43-PEO modified group had a significantly lower corrosion rate and maintained significantly higher mechanical properties than the unmodified. While corrosion rates were ∼50% lower in the WE43-PEO modified specimens, the local geometric features of corroding surfaces remained similar to the unmodified WE43 group, however evolving after almost the double amount of time. We were also able to quantitatively demonstrate that the PEO surface treatment on magnesium continued to protect samples from corrosion throughout the entire period tested, and not just in the early stages of corrosion. Using the results from the testing framework, the model parameters of the surface-based corrosion model were identified for both groups. This enabled, for the first time, in-silico prediction of the physical features of corrosion and the mechanical performance of both unmodified and PEO modified magnesium specimens. This simulation framework can enable future in-silico design and optimisation of bioabsorbable magnesium devices for load-bearing medical applications.

Mechanical properties of a bioabsorbable magnesium interference screw for anterior cruciate ligament reconstruction in various testing bone materials

Tears of the anterior cruciate ligament (ACL) negatively impact the stability and kinematics of the knee. Interference screws (ISs) are used for graft fixation in ACL reconstruction and provide sufficient fixation strength to withstand the patients' activities during the graft-to-bone integration process. Magnesium is a novel material used to manufacture IS given its strength and bioabsorbability. In previous studies, the selected magnesium IS design showed a better fixation performance in comparison to the conventional IS design due to its shape design and surface condition. In this study, bioabsorbable magnesium ISs were tested for their insertion (insertion torque and a number of turns to implement the IS) and fixation performance (pull-out and dynamic test). To obtain a reliable initial assessment of IS performance, ISs were implanted in 15 per cubic foot (PCF) Sawbones polyurethane foam blocks, Sawbones biomechanical tibia models with 17 PCF foam cores, and human cadaveric tibiae. Porcine tendons were used in the foam block pull-out test, and nylon ropes were used in all other test setups to prevent influences of the ligament graft material itself. In the pull-out test, the graft was subjected to tensile stress at a rate of 6 mm/min. For the dynamic test, 1000 cycles between 0 and 200 N were performed, followed by a final pull-out test. After each test, the tunnel widening pattern was observed by measuring the aspect ratio of the tunnel at the insertion site. The insertion torque lies within the normal insertion torque of the ISs as well as the average ligament tension before the insertion. In the foam block setup, the nylon rope showed a higher pull-out force than the porcine tendon. The comparison of each setup using nylon rope for both pull-out and pull-out after the dynamic test showed no significant difference between the foam block and cadaver setup. However, all tibia model setup shows unexpectedly high pull-out force due to the influence of its cortical layer. There were no statistically significant differences in tunnel widening between foam block-porcine tendon and foam block-nylon rope constructs. The pull-out resistance of magnesium ISs falls within the typical ACL tension range during daily activities. Even though the test results of the magnesium ISs are different in each bone material, the magnesium IS shows adequate fixation ability and workability during insertion without material failure.

Comparison between bioabsorbable magnesium and titanium compression screws for hallux valgus treated with distal metatarsal osteotomies: A meta-analysis.

In this review, we discuss the efficacy and safety of biodegradable magnesium screws compared to titanium screws in the treatment of hallux valgus (HV) in patients undergoing distal metatarsal osteotomy (DMO). Eligible scientific articles published prior to October 2022 were retrieved from the PubMed, Springer, ScienceDirect, and Cochrane Library databases. The terms used for searching included "hallux valgus", "distal metatarsal osteotomies", and "bioabsorbable magnesium screw" which were limited in the title or abstract through the text. The title and abstract were checked one by one to exclude the non-related studies. For primary identified studies and relevant systematic reviews, the full texts were accessed and browsed to finally include the eligible studies. No restriction was set on publication language and publication status. Two randomized-controlled trials (RCTs) and three non-RCTs that met the inclusion criteria were included. There was no significant difference in the American Orthopaedic Foot and Ankle Society (AOFAS) score, postoperative HV angle (HVA), intermetatarsal angle (IMA), Visual Analog Scale (VAS) score, soft tissue irritation, implant fracture, reoperation, and infection rates between two groups. Bioabsorbable magnesium compression screws show comparable clinical or radiological results to titanium compression screws in the treatment of HV in patients undergoing DMO.

Metal Oxide Coating On Biodegradable Magnesium Alloys

Magnesium is a biodegradable metal that has potential in orthopaedics. It has several advantages over other metallic materials because it is biocompatible and degradable now being used for biomedical applications, including elimination of stress shielding effects, enhancing degradation properties and enhancing biocompatibility concern in vivo, eliminating the second surgery for implant removal. Bioabsorbable magnesium (Mg) and related alloys have been limited in their usage because of its lower corrosion resistance. Surface alteration and functionality, in addition to basic alloying, is an important technique to deal with Mg and its alloys' reduced corrosion resistance. Magnesium's rapid depreciation however is a double-edged sword because it's critical to match bone renewal to material corrosion. As a result, calcium phosphate coatings have been proposed as a way to slow down corrosion. There are various possible calcium phosphate phases and their coating methods and can give a few distinct properties to various applications. Despite magnesium's lower melting point and greater reactivity, calcium phosphate coatings require precise settings to be effective. Because of their toxicity, non-biodegradability, and much higher cost, the recently used inorganic conversion coatings are less appealing and their application is limited. Conversion coatings are a viable alternative technology that is based on a cost- effective, environmentally friendly, and biodegradable organic component. Surface chelating functional groups in these compounds allow them to link with the magnesium/surface hydroxide layer while also providing anchoring groups for the polymer topcoat. Nanoreservoirs with multilayer inhibitors for active self-healing corrosion resistance thrive in this environment. This study examines the organic conversion coatings for Mg and its alloys in depth.

Intramedullary fixation of metacarpal and phalangeal bone fractures with bioabsorbable Mg K-wire in 20 cases.

The treatment of irreducible or severely displaced metacarpal and phalangeal bone fractures is still much debated. The recent development of the bioabsorbable magnesium K-wire is thought to allow effective treatment upon insertion via intramedullary fixation by minimizing articular cartilage injuries without discomfort until pin removal and drawbacks, such as pin track infection and metal plate removal. Therefore, this study investigated and reported the effects of intramedullary fixation with the bioabsorbable magnesium K-wire in unstable metacarpal and phalangeal bone fractures. This study included 19 patients admitted to our clinic for metacarpal or phalangeal bone fractures from May 2019 to July 2021. As a result, 20 cases were examined among these 19 patients. Bone union was observed in all 20 cases, with a mean bone union time of 10.5 (SD 3.4) weeks. Reduction loss was observed in six cases, all showing dorsal angulation with a mean angle of 6.6° (SD 3.5°) at 4.6weeks as compared with that noted in the unaffected side. The gas cavity upon H2 gas formation was first observed approximately 2weeks postoperatively. The mean DASH score was 33.5 for instrumental activity and 9.5 for work/task performance. No patient complained of notable discomfort after surgery. Intramedullary fixation with the bioabsorbable magnesium K-wire may be used for unstable metacarpal and phalanx bone fractures. This wire is expected to be a particularly favorable indication for shaft fractures, although care should be taken due to the possibility of complications related to rigidity and deformity.

Magnesium-Based Compression Screws in Acute Scaphoid Fractures and Nonunions.

Magnesium-based bioabsorbable osteosynthesis material continues to receive increasing attention. The following study documents our experience with bioabsorbable magnesium screws in scaphoid fracture treatment in hopes to capture further evidence and successful application. Eight acute scaphoid fractures and four nonunions were treated with the magnesium-based bioabsorbable compression screw MAGNEZIX®. Objective outcome was assessed by X-ray imaging and/or CT scan for bone healing. Clinical assessment was achieved using the modified Mayo Wrist Score. Patient-reported outcome measure was performed threefold via QuickDASH, PRWE, and EQ-5D-5L questionnaires in all patients. Follow-up was 32.5months (SD 18.7) in the acute fracture group and 31months (SD 7.4) in the nonunion group. Bone healing was achieved in all eight patients with acute scaphoid fractures and in three of four patients with scaphoid nonunion. The modified Mayo Wrist Score was 95 (SD 7.1) in fractures and 80 (SD 7.1) in nonunion patients during follow-up. QuickDASH score was 3.9 (SD 5.8) in fracture and 19.3 (SD 10.6) in nonunion patients. All but one patient (87,5%) with scaphoid fractures presented with a full health state during follow-up (EQ-5D-5L). Nonunion patients had problems in 10 out of 19 dimensions in EQ-5D-5L. Acute fractures presented with a score of 3.9 (SD 7.9) and nonunions with a score of 19.7 (SD 32.4) in PRWE total scoring during follow-up. Magnesium-based implants have excellent clinical outcomes when used for scaphoid fractures in eight presented cases and good to moderate clinical outcomes when used for nonunions in three of four presented cases. Additional studies are required to further analyze the differentiated applicability in scaphoid nonunion as well as overall performance when compared to non-absorbable screws in larger cohorts.

In Vitro Investigation of the Fixation Performance of a Bioabsorbable Magnesium ACL Interference Screw Compared to a Conventional Interference Screw.

An anterior cruciate ligament (ACL) reconstruction is a common treatment for patients with ACL rupture that aims to regain pre-injury knee stability and kinematics. During the ACL reconstruction, one method to fix the graft is the use of an interference screw (IS). The IS should provide initial stability and secure the graft during the healing period. In recent years, magnesium has emerged as an alternative material to permanent metal and polymer ISs. In addition, differences in designs, such as the shape of the IS, can influence the fixation performance of the IS. Therefore, in this biomechanical experiment, two different screw designs with two ligament materials were compared in an insertion and a pull-out test at a rate of 1 mm/s. The screw designs were a conventional polymer screw and a magnesium screw. Porcine tendon and nylon rope were used as ligament materials. All tests were performed in polyurethane foam blocks with 15 PCF density (Synbone AG, Switzerland). As a result, both screw designs required an insertion torque of less than 3 Nm. There was a significant difference between the porcine and nylon rope in pull-out tests for each screw design. The magnesium screw had the highest pull-out force at 412.14 ± 50.00 N for porcine tendon and 707.38 ± 21.81 N for nylon rope. There were no significant differences in tunnel widening (narrow-wide ratio) between each ligament material. The magnesium screw showed the lowest narrow-wide tunnel ratio, implying a better ability to compress the graft to the tunnel. In conclusion, a more optimized magnesium IS design resulted in better graft fixation and an improved ACL reconstruction outcome.

Long-term in vivo observations show biocompatibility and performance of ZX00 magnesium screws surface-modified by plasma-electrolytic oxidation in Göttingen miniature pigs.

Bioabsorbable magnesium implants for orthopedic fixation of bone have recently become available for different fields of indication. While general questions of biocompatibility have been answered, tailoring suitable degradation kinetics for specific applications as well as long-term tissue integration remain the focus of current research. The aim of this study was the evaluation of the long-term degradation behavior and osseointegration of Mg-Ca-Zn (ZX00MEO) based magnesium implants with plasma-electrolytic oxidation (PEO) surface modification (ZX00MEO-PEO) in comparison to non-surface modified implants in vivo and in vitro. Besides a general evaluation of the biological performance of the alloy over a prolonged period, the main hypothesis was that PEO surface modification significantly reduces implant degradation rate and improves tissue interaction. In vitro, the microstructure and surface of the bioabsorbable screws were characterized by SEM/EDS, cytocompatibility and degradation testing facilitating hydrogen gas evolution, carried out following ISO10993-5/-12 and ASTM F3268-18a/ASTM G1-03 (E1:2017). In vivo, screws were implanted in the frontal bone of Minipigs for 6, 12, and 18 months, following radiological and histomorphometric analysis. A slower and more uniform degradation and improved cytocompatibility could be shown for the ZX00MEO-PEO group in vitro. A significant reduction of degradation rate and enhanced bone formation around the ZX00MEO-PEO screws in vivo was confirmed. Proficient biocompatibility and tissue integration could generally be shown in vivo regardless of surface state. The tested magnesium alloy shows generally beneficial properties as an implant material, while PEO-surface modification further improves the bioabsorption behavior both in vitro and in vivo. STATEMENT OF SIGNIFICANCE: Devices from bioabsorbable Magnesium have recently been introduced to orthopedic applications. However, the vast degradation of Magnesium within the human body still gives limitations. While reliable in-vivo data on most promising surface treatments such as Plasma-electrolytic-Oxidation is generally scarce, long-time results in large animals are to this date completely missing. To overcome this lack of evidence, we studied a Magnesium-Calzium-Zinc-alloy with surface enhancement by PEO for the first time ever over a period of 18 months in a large animal model. In-vitro, surface-modified screws showed significantly improved cytocompatibility and reduction of degradation confirmed by hydrogen gas evolution testing, while in-vivo radiological and histological evaluation generally showed good biocompatibility and bioabsorption as well as significantly enhanced reduction of degradation and faster bone regeneration in the PEO-surface-modified group.

In vitro degradation and multi-antibacterial mechanisms of β-cyclodextrin@curcumin embodied Mg(OH)2/MAO coating on AZ31 magnesium alloy

It is a challenging task to prepare a coating on Mg alloys for desirable corrosion resistance, good antibacterial ability and biocompatibility. In this research work, an in-situ Mg(OH)2 coating incorporated with sodium alginate (SA) and β-cyclodextrin (β-CD)@curcumin (Cur) was formed on the surface of micro arc oxidation (MAO) coated AZ31 alloy via a low temperature hydrothermal method. Characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FT-IR) and scanning electron microscope (SEM) were employed to characterize the chemical composition and surface morphology of the coatings. The corrosion protection ability of the coatings was monitored via electrochemical polarization, hydrogen evolution and immersion tests. Photothermal antibacterial ability and cytocompatibility of the coatings were evaluated by plate counting method under the irradiation of 808 nm-near infrared light, in vitro cytotoxicity tests (MTT) and live/dead cell staining. The results indicate that a chelation of the organic molecules led to the formation of a MAO/(β[email protected])-SA-Mg(OH)2 coating with excellent corrosion protection, multi- antibacterial ability and almost no toxicity to the cells. Especially, the coating provided photothermal performance through the light absorption of Cur, which was encapsulated by β-CD to improve its bioavailability. SA enhanced the binding force between the drug and the substrate. This novel coating designated the potential application on bioabsorbable magnesium alloys.

Results of the Use of Bioabsorbable Magnesium Screws for Surgical Treatment of Mason Type II Radial Head Fractures.

In Mason classification type II radial head fractures, compared to plate fixation, fixation with cannulated headless screws and absorbable pins has been reported to provide more favorable postoperative outcomes, including less postoperative limitation in range of motion. The fact that radial head fractures are less prone to weight-bearing during fracture union further supports the use of absorbable screws as a suitable alternative treatment option in radial head fractures. This study aimed to perform fixation through open reduction using bioabsorbable magnesium screws for Mason type II radial head fractures and to report radiographic and clinical results. Among patients who visited the orthopedic department from April 2017 to August 2021, 22 with surgical indications were selected for participation. Radiographic tests were conducted at 2 weeks, 4 weeks, 8 weeks, 12 weeks, 6 months, and over 1 year after surgery to confirm the degree of bone union, reduction loss, and degree of H2 gas production. The Disabilities of the Arm, Shoulder and Hand (DASH) score, Mayo Elbow Performance Score (MEPS), hand grip power, and range of joint motion were measured at the 6-month follow-up to evaluate the clinical efficacy of the operation. Bone union was confirmed in all 22 cases, and the mean time to union was 10.2 weeks. DASH score was 22.27 on average and no patients complained of significant discomfort after the surgery. The mean MEPS was 91.1. The hand grip power of the affected hand was similar to that of the unaffected hand, being 1.19% weaker on average. These differences reached statistical significance (p = 0.002). The range of elbow joint motion was measured: mean flexion, 146.1°; mean extension, 1.4°; mean pronation, 88.2°; and mean supination, 87.9°. In treating Mason type II radial head fractures, the use of bioabsorbable screws made of magnesium showed satisfactory results in radiographic and clinical evaluations. Magnesium bioabsorbable screws can maintain sufficient stability at the fracture site and have the advantage of avoiding secondary operation for the removal of internal fixation devices.

Role of Solvent Used in Development of Graphene Oxide Coating on AZ31B Magnesium Alloy: Corrosion Behavior and Biocompatibility Analysis.

Clinical applications of bio-absorbable magnesium (Mg) and its alloys can be enhanced by increasing their corrosion resistance, using surface modification and functionality. In this study, we synthesized graphene oxide (GO) through improved Hummers' method and deposited it on biodegradable AZ31B Mg alloy for further characterization. Different suspensions of GO were prepared in various solvents, like deionized water, ethanol, and acetone by ultra-sonication. Electrophoretic deposition (EPD) was used to develop GO coatings on AZ31B Mg using different GO suspensions. Effect of various solvents on corrosion behavior, as well as in vitro biocompatibility, was studied. The optimized EPD parameters were 3 volts and 90 s for coating. Different characterization techniques were used to study GO and prepared coatings. Atomic force microscopy found that the average thickness of GO was ~1 nm. Electrochemical behavior of coatings was studied through electrochemical impedance spectroscopy (EIS) and Tafel analysis in Ringer's lactate solution. Tafel analysis revealed that GO coatings deposited by GO water suspension increased corrosion protection efficiency of AZ31B Mg alloy by ~94%. After 72 h incubation in MC3T3-E1 osteoblast cells extract, in vitro analysis was performed to determine the cell viability and biocompatibility of the GO- coated and bare Mg samples. GO coatings deposited by GO water suspension demonstrated ~2× cell viability, as well as nontoxicity and better biocompatibility compared to the bare and other GO-coated Mg samples.

Evaluation of drug-eluting nanoparticle coating on magnesium alloy for development of next generation bioabsorbable cardiovascular stents.

Since the introduction of bioabsorbable magnesium alloys into cardiovascular stent technology, many researches have been conducted to improve these metallic scaffolds. Various coatings and different coating techniques, super plastic deformation techniques and synthesizing different Mg-based alloy are examples of such efforts. In this study, a magnesium based alloy (WE43) was coated with dexamethasone loaded polymeric nanoparticles via electrospraying method. Drug release behavior, drug inhibitory effects, surface properties and cell responses to the surface were evaluated. Drug release profile was investigated and compared to drug-loaded nanoparticle on stainless steel as a control. The inhibitory effects of the drug-loaded nanoparticle coatings on smooth muscle cells was evaluated via MTT assay. Endothelial cells response to the surface was investigated by SEM. The results showed that contact angle and roughness of the surface were 131° and 600-800nm, respectively. Drug release studies showed a burst release less than 30% after 24h which followed by nearly zero order release kinetic. MTT assay showed that SMCs viability decreased to 60% and 25% after 24 and 72h, respectively. SEM images indicated proper adhesion and proliferation of endothelial cells on the surface. The findings suggest that nanoparticle-coated surfaces could effectively inhibit SMC proliferation meanwhile provide desirable surface features for adhesion and proliferation of endothelial cell on magnesium alloy based stents.

Biohybrid elastin-like venous valve with potential for in situ tissue engineering.

Chronic venous insufficiency (CVI) is a leading vascular disease whose clinical manifestations include varicose veins, edemas, venous ulcers, and venous hypertension, among others. Therapies targeting this medical issue are scarce, and so far, no single venous valve prosthesis is clinically available. Herein, we have designed a bi-leaflet transcatheter venous valve that consists of (i) elastin-like recombinamers, (ii) a textile mesh reinforcement, and (iii) a bioabsorbable magnesium stent structure. Mechanical characterization of the resulting biohybrid elastin-like venous valves (EVV) showed an anisotropic behavior equivalent to the native bovine saphenous vein valves and mechanical strength suitable for vascular implantation. The EVV also featured minimal hemolysis and platelet adhesion, besides actively supporting endothelialization in vitro, thus setting the basis for its application as an in situ tissue engineering implant. In addition, the hydrodynamic testing in a pulsatile bioreactor demonstrated excellent hemodynamic valve performance, with minimal regurgitation (<10%) and pressure drop (<5 mmHg). No stagnation points were detected and an in vitro simulated transcatheter delivery showed the ability of the venous valve to withstand the implantation procedure. These results present a promising concept of a biohybrid transcatheter venous valve as an off-the-shelf implant, with great potential to provide clinical solutions for CVI treatment.