Introduction. Local anaesthetic has been reported to have a detrimental effect on human chondrocytes both in vitro and in vivo. Magnesium, an NMDA-receptor antagonist, may be an alternative intra-articular analgesic agent following arthroscopy. We aimed to report the dose response effect of commonly used local anaesthteitc on chondrocyte viability and also report on the effect of adding magnesium to local anaesthetic. Methods. Human chondrocytes were grown under standard conditions. Cells were exposed to either lignocaine (0.5, 1, 2%), levobupivacaine (0.125, 0.25, 0.5%), bupivacaine (0.125, −.25, 0.5%) or ropivacaine (0.1875, 0.375, 0.75%) for 15 minutes. Cells were also exposed to a local anesthetic agent with the addition of magnesium (10, 20, or 50%). Cells exposed to media or saline served as controls. The MTS assay was used to assess cell viability 24-hours after exposure. Results. One-way ANOVA showed an expected dose response in all local anaesthetic groups with the exception of lignocaine. Magnesium alone was no more toxic than normal saline (P>0.3). 50% magnesium showed similar effect on cell viability to the least toxic local anaesthetic (lignocaine 1%, P=0.31). The addition of magnesium to the local anesthetic agents resulted in greater cell viability than when cells were treated with the respective local anaesthetic alone (lignocaine (P=0.033), levobupivacaine (P=0.007), bupivacaine (P<0.001), ropivacaine (P<0.001)). Conclusion. We have shown that cell viability is greater in the presence of magnesium than selected local anaesthetics and also with the addition of magnesium to local anaesthetic compared to the local anesthetic agent alone. We believe that these findings offer support to an alternative intra-articular analgesia following arthroscopy

Orthopedic implants containing biodegradable magnesium have been used for fracture repair with considerable efficacy; however, the underlying mechanisms by which these implants improve fracture healing remain elusive. Here we show the formation of abundant new bone at peripheral cortical sites after intramedullary implantation of a pin containing ultrapure magnesium into the intact distal femur in rats. This response was accompanied by substantial increases of neuronal calcitonin gene-related polypeptide-a (CGRP) in both the peripheral cortex of the femur and the ipsilateral dorsal root ganglia (DRG). Surgical removal of the periosteum, capsaicin denervation of sensory nerves or knockdown in vivo of the CGRP-receptor-encoding genes Calcrl or Ramp1 substantially reversed the magnesium-induced osteogenesis that we observed in this model. Overexpression of these genes, however, enhanced magnesium-induced osteogenesis. We further found that an elevation of extracellular magnesium induces magnesium transporter 1 (MAGT1)-dependent and transient receptor potential cation channel, subfamily M, member 7 (TRPM7)-dependent magnesium entry, as well as an increase in intracellular adenosine triphosphate (ATP) and the accumulation of terminal synaptic vesicles in isolated rat DRG neurons. In isolated rat periosteum-derived stem cells, CGRP induces CALCRL- and RAMP1-dependent activation of cAMP-responsive element binding protein 1 (CREB1) and SP7 (also known as osterix), and thus enhances osteogenic differentiation of these stem cells. Furthermore, we have developed an innovative, magnesium-containing intramedullary nail that facilitates femur fracture repair in rats with ovariectomy-induced osteoporosis. Taken together, these findings reveal a previously undefined role of magnesium in promoting CGRP-mediated osteogenic differentiation, which suggests the therapeutic potential of this ion in orthopedics

Bone defects and fractures, caused by injury, trauma or tumour resection require hospital treatment and temporary loss of mobility, representing an important burden for societies and health systems worldwide. Autografts are the gold standard for promoting new bone formation, but these may provide insufficient material and lead to donor site morbidity and pain. We previously showed that Fibrinogen (Fg) scaffolds promote bone regeneration in vivo (1), and that modifying them with 10mM of Magnesium (Mg) ions modulates macrophage response in vitro and in vivo (2). Also, we showed that Extracellular Vesicles (EV) secreted by Dendritic Cells (DC) recruit Mesenchymal Stem/Stromal Cells (MSC)(3). Herein, we aim to functionalize FgMg scaffolds with DC-EV, to promote recruitment and osteogenic differentiation of MSC. Scaffolds were produced by freeze-drying (2). Ethical permission was sought for all studies. Primary human peripheral blood monocyte-derived DC were cultured, their secreted EV were isolated by differential (ultra)-centrifugation and characterised by transmission electron microscopy and nanoparticle tracking analysis (3). Bone marrow MSC were used to determine the impact of EV-functionalized scaffolds through migration assays and their osteogenic differentiation was assessed by Alizarin Red staining. Fg and FgMg scaffolds functionalized with EV were characterized. Fg and FgMg scaffolds functionalized with DC-secreted EV were more efficient at recruiting MSC than scaffolds alone. MSC cultured on FgMg scaffolds showed significantly increased calcium deposits, in comparison with those cultured on Fg scaffolds. Fg scaffold modification by Mg promotes MSC osteogenic differentiation, while their functionalization with DC-secreted EV acts to promote MSC recruitment. This renders the FgMg-EV functionalized scaffolds an attractive material to promote new bone formation. Acknowledgments: Work funded by Orthoregeneration Network (ON Pilot Grant Spine 2021, EVS4Fusion). MCT supported by ERASMUS+ program

Critical size bone defects are frequently caused by accidental trauma, oncologic surgery, and infection. Distraction osteogenesis (DO) is a useful technique to promote the repair of critical size bone defects. However, DO is usually a lengthy treatment, therefore accompanied with increased risks of complications such as infections and delayed union. Herein, we developed an innovative intramedullary biodegradable magnesium (Mg) nail to accelerate bone regeneration in critical size bone defect repair during DO. We observed that Mg nail induced almost 4-fold increase of new bone formation and over 5-fold of new vessel formation at 2 weeks after distraction. Mg nail upregulated the expression of calcitonin gene-related peptide (CGRP) in the new bone as compared with the DO alone group. We further revealed that blockade of the sensory nerve by overdose capsaicin blunted Mg nail enhanced critical size bone defect repair during the DO process. Moreover, inhibitors/antagonist of CGRP receptor, FAK, and VEGF receptor blocked the Mg nail stimulated vessel and bone formation. In summary, we revealed, for the first time, a CGRP-FAK-VEGF signaling axis linking sensory nerve and endothelial cells, which may be the main mechanism underlying Mg-enhanced critical size bone defect repair when combined with DO, suggesting a great potential of Mg implants in reducing DO treatment time for clinical applications

Introduction. Local anaesthetic has been reported to have a potentially detrimental effect on human chondrocytes both in vitro and in vivo. Due to chondroproliferative effects, magnesium may be an alternative intra-articular analgesic agent following arthroscopy. We aimed to examine the dose response effect of commonly used local anaesthetics on chondrocyte viability and also to report on the effect of adding magnesium to the local anesthetic agent. Methods. Human chondrocytes were grown under standard culture conditions. Cells were exposed to either lignocaine (0.5, 1, 2%), levobupivacaine (0.125, 0.25, 0.5%), bupivacaine (0.125, 0.25, 0.5%) or ropivacaine (0.1875, 0.375, 0.75%) for 15 minutes. Cells were also exposed to a local anesthetic agent with the addition of magnesium (10, 20, or 50%). Cells exposed to culture media or saline served as controls. The MTS assay was used to assess cell viability 24 hours after exposure. One-way ANOVA were used to test for statistical significance. Results. One-way ANOVA showed a dose response in all local anesthetic groups with the exception of lignocaine with higher concentrations leading to lower levels of cell viability. Magnesium alone was no more toxic than normal saline (P>0.3) compared to untreated cells. 50% magnesium showed similar effect on cell viability to the least toxic local anesthetic (lignocaine 1%, P=0.31). The addition of magnesium to the local anesthetic agents resulted in greater cell viability than when cells were treated with the respective local anaesthetic alone (lignocaine (P=0.033), levobupivacaine (P=0.007), bupivacaine (P<0.001), ropivacaine (P<0.001)). Conclusion. We have showed that cell viability is improved with the addition of magnesium to local anaesthetic compared to the local anesthetic agent alone. We believe that these findings offer support to an alternative intra-articular analgesia following arthroscopy. However, the optimum doses and combinations of local anaesthetic and magnesium are yet to be shown

Aims. Mendelian randomization (MR) is considered to overcome the bias of observational studies, but there is no current meta-analysis of MR studies on rheumatoid arthritis (RA). The purpose of this study was to summarize the relationship between potential pathogenic factors and RA risk based on existing MR studies. Methods. PubMed, Web of Science, and Embase were searched for MR studies on influencing factors in relation to RA up to October 2022. Meta-analyses of MR studies assessing correlations between various potential pathogenic factors and RA were conducted. Random-effect and fixed-effect models were used to synthesize the odds ratios of various pathogenic factors and RA. The quality of the study was assessed using the Strengthening the Reporting of Observational Studies in Epidemiology using Mendelian Randomization (STROBE-MR) guidelines. Results. A total of 517 potentially relevant articles were screened, 35 studies were included in the systematic review, and 19 studies were eligible to be included in the meta-analysis. Pooled estimates of 19 included studies (causality between 15 different risk factors and RA) revealed that obesity, smoking, coffee intake, lower education attainment, and Graves’ disease (GD) were related to the increased risk of RA. In contrast, the causality contribution from serum mineral levels (calcium, iron, copper, zinc, magnesium, selenium), alcohol intake, and chronic periodontitis to RA is not significant. Conclusion. Obesity, smoking, education attainment, and GD have real causal effects on the occurrence and development of RA. These results may provide insights into the genetic susceptibility and potential biological pathways of RA. Cite this article: Bone Joint Res 2023;12(9):601–614

Degradable implants made of magnesium alloys as osteosynthesis material for weight-bearing bone are at present a main research area. With regards to biocompatibility, a MA with 0.8 wt. % Calcium (MgCa(0.8)) has been shown to possess advantageous qualities. Long-term investigations in animal models however, showed that the degradation rate of this magnesium alloy was relatively rapid and therefore the mechanical properties decreased early during the implantation period. An implant for osteosynthesis in weight-bearing bones however needs to exhibit adequate stability during the first few weeks of fracture healing. This cannot sufficiently be assured by the MgCa(0.8) alloy. It has been suggested in the literature, that the degradation rate of MA could be reduced using a fluoride coating. Therefore it was the aim of this study to investigate, whether the coating of degradable MA MgCa(0.8) implants with magnesium fluoride layer leads to decreased degradation rate and in consequence to an improvement of the mechanical properties using an animal model. Extruded pins (2.5 mm x 25 mm) of MgCa(0.8) were produced. Twenty of these pins were coated with a fluoride layer by submerging the implants in a bath with 40% hydrofluoric acid. With this procedure, the pins were covered with a thin (150–200μm thickness) MgF2 layer. Coated and uncoated pins were intramedullary implanted into both tibiae of ten New Zealand White Rabbits. Three and six months after surgery five animals of each group were euthanized and the tibiae were explanted for further analysis. Micro-computed tomography (μCT) and scanning electron microscopy (SEM) were performed of the explanted pins. In order to investigate changes of the mechanical properties, 3-point bending tests were carried out with MgCa(0.8) pins at the initial state and with the explanted pins, with and without the fluoride layer at both times. In addition, the mass loss of the pins was determined. To evaluate the degradation process of the MgCa(0.8) pins with the MgF2 layer, micrographs and element analyses (EDX) were accomplished after the three point bending tests. During the investigation period, the rabbits showed no signs of lameness or pain. The MgCa(0.8) alloy and the MgCa(0.8) alloy with the MgF2 layer showed significant differences regarding the mechanical properties in dependence of the implantation duration. Generally, the mechanical resistance decreases with increasing implantation time. The 3-point bending test showed, that the values of maximal force of the coated MgCa(0.8) implants after three month implantation duration were lower than those of the uncoated implants. After an implantation duration of six months, the values of maximal force of the implants coated with MgF2 were higher than those of the uncoated implants. Regarding the implant mass, the coated and uncoated MgCa(0.8) implants showed a loss of mass during the implantation period. The mass loss of the coated implants was only slightly lower. This difference was minor after three months and more obviously after six months. With μCT new endosteal bone formation could be seen close to all implants. A decrease of the cross section dimension could be demonstrated with μCT and SEM and changes of the surfaces due to pitting corrosion could be demonstrated in both the coated and uncoated MgCa(0.8) implants on the whole length, which was more obvious after six months. The micrographs showed corroded surfaces but not preferred corrosion on the grain boundaries. The element analysis showed a degradation layer on the implant surface, which was more bulky on implants after six month implantation duration. The mapping shows, that the fluoride molecules are clearly visible after three and six months around the margin of the implant. With the results of this study it could be demonstrated, that the coating of the MgCa(0.8) implants with a flouride layer did not have a positive influence on the mechanical properties and the degradation rate of the implant in the bone. This leads to the conclusion that MgF2-coated MgCa(0.8) implants are also not suitable for osteosynthesis in weightbearing bones

Magnesium calcium alloys are promising candidates for an application as biodegradable osteosynthesis implants [1,2]. As the success of most internal fracture fixation techniques relies on safe anchorage of bone screws, there is necessity to investigate the holding power of biodegradable magnesium calcium alloy screws. Therefore, the aim of the present study was to compare the holding power of magnesium calcium alloy screws and commonly used surgical steel screws, as a control, by pull-out testing. Magnesium calcium alloy screws with 0.8wt% calcium (MgCa0.8) and conventional surgical steel screws (S316L) of identical geometries (major diameter 4mm, core diameter 3mm, thread pitch 1mm) were implanted into both tibiae of 40 rabbits. The screws were placed into the lateral tibial cortex just proximal of the fibula insertion and tightened with a manual torque gauge (15cNm). For intended pull-out tests a 1.5mm thick silicone washer served as spacer between bone and screw head. Six animals with MgCa0.8 and four animals with S316L were followed up for 2, 4, 6 and 8 weeks, respectively. Thereafter the rabbits were sacrificed. Both tibiae were explanted, adherent soft tissue and new bone was carefully dissected around the screw head. Pull-out tests were carried out with an MTS 858 MiniBionix at a rate of 0.1mm/sec until failure of the screw or the bone. For each trial the maximum pull-out force [N] was determined. Statistical analysis was performed (ANOVA, Student's t-test). Both implant materials were tolerated well. Radiographically, new bone was detected at the implantation site of MgCa0.8 and S316L, which was carefully removed to perform pull-out trials. Furthermore, periimplant accumulations of gas were radiographically detected in MgCa0.8. The pull-out force of MgCa0.8 and S316L did not significantly differ (p = 0.121) after two weeks. From 6 weeks on the pull-out force of MgCa0.8 decreased resulting in significantly lower pull-out values after 8 weeks. Contrary, S316L pull-out force increased throughout the follow up. Thus, S316L showed significantly higher pull-out values than MgCa0.8 after 4, 6 and 8 weeks (p<0.001). MgCa0.8 showed good biocompatibility and pull-out values comparable to S316L in the first weeks of implantation. Thus, its application as biodegradable osteosynthesis implant is conceivable. Further studies are necessary to investigate whether the reduced holding power of MgCa0.8 is sufficient for secure fracture fixation. In addition, not only solitary screws, but also screw-plate-combinations should be examined over a longer time period. Acknowledgements. The study is part of the collaborative research centre 599 funded by the German Research Foundation

The ideal bone substituting biomaterials should possess bone-mimicking mechanical properties; have of porous interconnected structure, and adequate biodegradation behaviour to enable full recovery of bony defects. Direct metal printed porous scaffolds hold potential to satisfy all these requirements and were additively manufactured (AM) from atomized WE43 magnesium alloy powder with grain sizes between 20 and 60 μm. Their micro-structure, mechanical properties, degradation behavior and biocompatibility was then evaluated in vitro. Firstly, post-processing values nicely followed design parameters. Next, Young's moduli were similar to that of trabecular bone (i.e., E = 700–800 MPa) even after 28 days of simulated in vivo-like corrosion by in vitro immersion. Also, a relatively moderate hydrogen evolution, corresponding to a calculated 19.2% of scaffold mass loss, was in good agreement with 20.7% volume reduction as derived from reconstructed μCT images. Finally, only moderate cytotoxicity (i.e., level 0, <25%), even after extensive ISO 10993-conform testing for 72 h using MG-63 cells, was determined using WE43 extracts (2 way ANOVA, post-hoc Tukey's multiple comparisons test; α = 0.05). Cytotoxicity was further evaluated by direct live-dead staining assays, revealing a higher cell death in static culture. However, intimate cell-metal contact was observed by SEM. In summary, while pure WE43 may not yet be an ideal surface for cell adhesion, this novel AM process allows for adjusting biodegradation through topological design. Our approach holds tremendous potential to develop functional and biodegradable implants for orthopaedic applications

There is no optimal therapy to stop or cure chondral degeneration in osteoarthritis (OA). Beside cartilage, subchondral bone is involved. The often sclerotic bone is mechanically less solid which in turn influences negatively chondral quality. Microfracturing as therapeutic technique aims to enhance bone quality but is applied only in smaller cartilage lesions. The osteoproliferative properties of Magnesium (Mg) have been shown repeatedly. 1-3. The present study examined the influence of micro-scaled Mg cylinders compared to sole drilling in an OA model. Ten New Zealand White rabbits underwent anterior crucial ligament transection. During 12 weeks after surgery, the animals developed OA as previously described. 4. In a second surgery, half of the animals received 20 drill holes (ø 0.5mm) and the other half received 20 drill holes, which were additionally filled with one Mg cylinder each. Extracapsular plication was performed in all animals. During the follow-up of 8 weeks three µ-computed tomographic (µCT) scans were performed: immediately after surgery and after four and eight weeks. Changes of bone volume, trabecular thickness and bone density were calculated and compared. µCT evaluation showed an increase in bone volume and trabecular thickness in both groups. This increase was significantly higher in rabbits which received Mg cylinders showing thrice as high values for both parameters (bone volume: Mg group +44.5%, drilling group +15.1%, p≤0.025; trabecular thickness: Mg group +53.2%, drilling group +16.9%, p≤0.025). Also bone density increased in both groups, but on a distinctly lower level and with no significant difference. Although profound higher bone volume was found after implantation of Mg cylinders, µCT showed similar levels of bone density indicating adequate bone quality in this OA model. Macroscopic and histological evaluation of cartilage condition have to reveal possible impact on OA progression. Additionally, current examination implement different alloys and influence on lameness

Patellar fractures account for approximately 1% of all fractures. Open reduction and internal fixation is recommended to restore extensor continuity and articular congruity. However, complications such as nonunion and symptomatic hardware, still exist. Furthermore, there is a risk of re-fracturing of the healed bone during the removal of the implants. Magnesium (Mg), a biodegradable metal, has elastic moduli and compressive yield strength that are comparable to those of natural bone. Our previous study showed that released Mg ions enhanced fracture healing. However, Mg-based implants degrade rapidly after implantation and lead to insufficient mechanical strength to support the fracture. Microarc oxidation (MAO) is a metal surface coating that reduces corrosion. We hypothesized that Mg pins, with or without MAO, would enhance fracture healing radiologically, mechanically, and histologically, while MAO would decrease degradation of Mg pins. Patellar fracture was performed on forty-eight 18-week-old female New Zealand White rabbits according to established protocol. Briefly, the patella is osteotomized transversely and a tunnel (1.1mm) was drilled longitudinally through the two bone fragments. A pin (1 mm, stainless steel, Mg, or MAO-Mg) was inserted into the tunnel. The reduced construct was stabilized with a figure-of-eight band wire (⊘ 0.6 mm stainless steel wire). Cast immobilization was applied for 6 weeks. The rabbits were euthanized at week 8 and 12 post-operation. Microarchitecture and mechanical properties of the repaired patella were analyzed with microCT and tensile testing respectively. Histological sections of the repaired patella were stained. To evaluate the effect of the MAO treatment on degradation rate of Mg pin, the volume of the Mg pins in the patella was measured with microCT. At week 8, both Mg and Mg-MAO showed higher ratio of bone volume to tissue volume (BV/TV) than the control while there was no significant different between Mg and Mg-MAO. At week 12, Control, Mg, and Mg-MAO groups showed enlarged patella when compared to the normal patella. Tissue volume (TV) and bone volume (BV) of the patella in Mg and Mg-MAO were larger than those in the Control group. However, the Control had higher ratio of bone volume to tissue volume (BV/TV), TV density, and BV density than Mg and Mg-MAO. Tensile testing showed that the mechanical properties of the repaired patella (failure load, stiffness, ultimate strength, and energy-to-failure) of Mg and Mg-MAO were higher than that of the control at both week 8 and week 12. Histological analysis showed that there was significant new bone formation in the Mg and Mg-MAO group compared with the Control group at week 8 and 12. The degradation rate of the MAO-coated Mg pins was significantly slower than those without MAO at week 8 but no significant difference was detected at week 12. Mechanical, microarchitectural, and histological assessments showed that Mg pins, with or without MAO, enhanced fracture healing of the repaired patella compared to the Control. MAO treatment enhanced the corrosion resistance of the Mg pins at the early time point

Aims

Adenosine, lidocaine, and Mg²⁺ (ALM) therapy exerts differential immuno-inflammatory responses in males and females early after anterior cruciate ligament (ACL) reconstruction (ACLR). Our aim was to investigate sex-specific effects of ALM therapy on joint tissue repair and recovery 28 days after surgery.

Summary Statement. Magnesium has a number of qualities suitable for bioresorbable metallic implants. However, high corrosion rate and formation of hydrogen gas can compromise its performance. Combining magnesium with calcium phosphate improves magnesium's biocompatibility by decreasing gas formation and increasing bone remodeling. Introduction. Clinical problems like risk of postoperative infection and increased incidence of pediatric trauma requiring surgical intervention raised the need for temporary orthopedic implants that would resorb after the bone healing is complete. This would decrease high costs associated with repeated surgeries, minimise recovery times, decrease the risk of postoperative infections, and thus promote higher quality of life to the patients. The specific requirement for orthopedic implants, aside from being bioresorbable, is the ability to bear high loads. Magnesium was suggested as a suitable material for these purposes because it is biocompatible; has excellent mechanical properties; is natural for human body, and seems to stimulate new bone formation. However, an important problem with magnesium is high corrosion rate with consistent hydrogen gas formation on contact with fluids. This in vivo study focuses on investigation of new magnesium-based implants specifically designed to minimise hydrogen gas formation. Methods. Four types of degradable magnesium-based materials were tested for biocompatibility in this study: Magnesium-Hydroxyapatite implants (Mg-HA); Magnesium-Calcium Phosphate Cement (Mg-CPC); alloy of 96% Magnesium and 4% Yttrium (W4); and 99.95% pure magnesium which was a control group. Biomaterials were operated into 33 male New Zealand white rabbits. The animals were sacrificed after 6 and 12 weeks after which the samples were embedded into Epon, paraffin and Technovit resin. The staining was done with TRAP, hematoxylin eosin and toluidine blue. Additionally, TEM and immunohistochemical analysis were performed. The data was analysed both qualitatively and quantitatively by Statistical Package for the Social Sciences (SPSS, v18, SPSS Inc, Chicago, IL). Results. Mg-CPC showed the best performance in this study. New bone formation was significantly more prevalent in Mg-CPC group while gas formation was significantly less comparing to the other materials. Mg-HA had the worst properties due to extremely fast degradation already at 6 weeks, the least amount of new bone formation, and the lowest amount of osteoclasts and multinucleated cells in the implantation site. Pure magnesium and W4 had similar properties: both were surrounded with corrosion layer, and the gas volumes were significantly higher in these two groups compared to other materials. Discussion/Conclusion. New bone was seen forming either in direct contact to implants or around the gas bubbles. The later can be interpreted as body's reaction to protect from gas spreading. Mg-HA's degradation rate was far too fast and this is unacceptable for orthopedic fractures which often require several months to heal and that experience much load. Pure magnesium and W4 although maintained their integrity, were surrounded by corrosion layer and gas bubbles that were bigger in diameter than in the other groups. These findings could compromise implant stability. Mg-CPC was the most biocompatible; it showed significantly higher amount of osteoclasts which is a first sign of bone remodeling. It had also significantly less gas production than other groups. These results show that magnesium's biocompatibility could be improved by combining it with other suitable materials, such as calcium phosphate

Aims. This study is a prospective, non-randomized trial for the treatment of fractures of the medial malleolus using lean, bioabsorbable, rare-earth element (REE)-free, magnesium (Mg)-based biodegradable screws in the adult skeleton. Methods. A total of 20 patients with isolated, bimalleolar, or trimalleolar ankle fractures were recruited between July 2018 and October 2019. Fracture reduction was achieved through bioabsorbable Mg-based screws composed of pure Mg alloyed with zinc (Zn) and calcium (Ca) ( Mg-Zn0.45-Ca0.45, in wt.%; ZX00). Visual analogue scale (VAS) and the presence of complications (adverse events) during follow-up (12 weeks) were used to evaluate the clinical outcomes. The functional outcomes were analyzed through the range of motion (ROM) of the ankle joint and the American Orthopaedic Foot and Ankle Society (AOFAS) score. Fracture reduction and gas formation were assessed using several plane radiographs. Results. The follow-up was performed after at least 12 weeks. The mean difference in ROM of the talocrural joint between the treated and the non-treated sites decreased from 39° (SD 12°) after two weeks to 8° (SD 11°) after 12 weeks (p ≤ 0.05). After 12 weeks, the mean AOFAS score was 92.5 points (SD 4.1). Blood analysis revealed that Mg and Ca were within a physiologically normal range. All ankle fractures were reduced and stabilized sufficiently by two Mg screws. A complete consolidation of all fractures was achieved. No loosening or breakage of screws was observed. Conclusion. This first prospective clinical investigation of fracture reduction and fixation using lean, bioabsorbable, REE-free ZX00 screws showed excellent clinical and functional outcomes. Cite this article: Bone Joint Res 2020;9(8):477–483

Bone allograft is the most widely accepted approach in treating patients suffering from large segmental bone defect regardless of the advancement of synthetic bone substitutes. However, the long-term complications of allograft application in term of delayed union and nonunion were reported due to the stringent sterilization process. Our previous studies demonstrated that the incorporation of magnesium ions (Mg2+) into biomaterials could significantly promote the gene up-regulation of osteoblasts and new bone formation in animal model. Hence, our group has proposed to establish an Mg2+ enriched tissue microenvironment onto bone allograft so as to enhance the bone healing. The decellularization and gamma irradiation process were performed on bovine bone allograft and followed by magnesium plasma treatment. To evaluate the biocompatibility and bioactivity, materials characterizations, in vitro and in vivo studies were conducted, respectively. Mg composite layer on bone surface ranged from 500nm to ∼800nm thick. The cell viability on magnesium enriched allograft was significantly higher than that of the control. The ALP gene expression of hTMSCs in the group of PIII&D treated samples was highly up-regulated. The bone regeneration ability of Mg modified bone allograft implanted in animal model was significantly superior than the control after 2-month post-operation

Device-associated bacterial infections are a major and costly clinical challenge. This project aimed to develop a smart new biomaterial for implants that helps to protect against infection and inflammation, promote bone growth, and is biodegradable. Gallium (Ga) doped strontium-phosphate was coated on pure Magnesium (Mg) through a chemical conversion process. Mg was distributed in a graduated manner throughout the strontium-phosphate coating GaSrPO4, with a compact structure and a Ga-rich surface. We tested this sample for its biocompatibility, effects on bone remodeling and antibacterial activities including Staphylococcus aureus, S. epidermidis and E. coli - key strains causing infection and early failure of the surgical implantations in orthopaedics and trauma. Ga was distributed in a gradient way throughout the entire strontium-phosphate coating with a compact structure and a gallium-rich surface. The GaSrPO4 coating protected the underlying Mg from substantial degradation in minimal essential media at physiological conditions over 9 days. The liberated Ga ions from the coatings upon Mg specimens inhibited the growth of bacterial tested. The Ga dopants showed minimal interferences with the SrPO4 based coating, which boosted osteoblasts and undermined osteoclasts in in vitro co-cultures model. The results evidenced this new material may be further translated to preclinical trial in large animal model and towards clinical trial. Acknowledgements: Authors are grateful to the financial support from the Australian Research Council through the Linkage Scheme (ARC LP150100343). The authors acknowledge the facilities, and the scientific and technical assistance of the RMIT University and John Curtin School of Medical Research, Australian National University

Prosthetic Joint Infection (PJI) is a devastating complication that can occur after total joint replacement surgery. With increasing antimicrobial resistance, there is a need for non-antibiotic approaches to treat and prevent PJI. Doping calcium phosphates with antimicrobial ions shows promise for these purposes. This systematic review aims to search and summarise the evidence-base for the potential of calcium phosphates doped with different antimicrobial ions. A systematic review was conducted on PubMed, Embase, Web-Of-Science, Cochrane Library and Emcare of in vitro and animal studies on the antimicrobial activity of (co)substituted calcium phosphates according to PRIMSA guidelines.. The research protocol, listing search terms and in/exclusion criteria, was registered a priori at . https://doi.org/10.7910/DVN/HEP18U. Data was extracted regarding ions, micro-organisms and antimicrobial activity. The search retrieved 1017 hits of which 148 papers were included. The substitution of 33 different ions was reported. Silver (n= 46), zinc (n=39), copper (n=18) and magnesium (n=14) were the most commonly doped ions. 36 different micro-organisms were studied of which E. coli (n=109), S. aureus (n=99), and C. albicans (n=22) were the most common. 6 different outcomes were reported, most commonly the K-ratio (n=53), the log CFU (n=41) and the bacterial inhibition zone (n=39). A validated outcome for the evaluation of biofilm prevention was lacking. There was considerable heterogeneity in studied ions, micro-organisms and reported outcomes. A lack of clearly defined reporting guidelines in the field of antimicrobial materials has led to the use of clinically irrelevant micro-organisms and a general lack of consistency of the methods used and the reported results. Currently, there is no universally accepted measure for the effectiveness required from biomaterials for treatment and prevention of PJI

Osteoarthritis (OA) is an inflammatory disease affecting the complete synovial joint including the cartilage layer and the subchondral bone plate. Due to the multifactorial causes and the not yet completely resolved molecular mechanisms, it lacks a gold standard treatment to mitigate OA. Hence, biomaterials capable of delaying or preventing OA are a promising alternative or supplement to antiphlogistic and surgical interventions. Magnesium (Mg) and its alloys are among the promising biomaterials with osteoinductive effects. This work investigated the impact of Mg micro cylinders (length ≈of 1.0 mm and width of 0.5 mm) in vitro, in favoring joint regeneration together with preventing OA progression. Therefore, a mesenchymal stem cell line (SCP-1) was applied in order to assess the compatibility of the degradable material. Furthermore, an in vitro OA model utilizing SCP-1 cells based on the supplementation of the cytokines; IL-1β, TNF-α was established and disclosed the capability of Mg microparticles in differentiating SCP-1 cells into chondrogenic and osteogenic lineages proven through extracellular matrix staining and gene marker analysis. A concentration above 10 mM revealed a reduction in the cell viability by 50 %. An increase in the expression of collagens especially and proteoglycans (COL2A1, Aggrecan) as extracellular matrix proteins as well as an increase in osteogenic marker (ALP, BMP2) favoring the mineralization process were observed. The inflammatory condition reduced the viability and productivity of the applied stem cell line. However, the application of Mg microparticles induced a cell recovery and reduction of inflammation marker such as MMP1 and IL6. The cytocompatible and the ability of Mg microparticles in supporting bone and cartilage repair mechanisms in vitro even under inflammatory conditions make biodegradable Mg microparticles a suitable implant material to treat OA therapy. Acknowledgements: This project OAMag was funded by the German Research Foundation (project number 404534760). The author thank Dr. Björn Wiese (hereon) for the production of Mg based material and Prof. Böcker (MUM Musculoskeletal University Center Munich) for the provision of SCP-1 cell line

Over the last decades, biodegradable metals emerged as promising materials for various biomedical implant applications, aiming to reduce the use of permanent metallic implants and, therefore, to avoid additional surgeries for implant removal. However, among the important issue to be solved is their fast corrosion - too high to match the healing rate of the bone tissue. The most effective way to improve this characteristic is to coat biodegradable metals with substituted calcium phosphates. Tricalcium phosphate (β-TCP) is a resorbable bioceramic widely used as synthetic bone graft. In order to modulate and enhance its biological performance, the substitution of Ca2+ by various metal ions, such as strontium (Sr2+), magnesium (Mg2+), iron (Fe2+) etc., can be carried out. Among them, copper (Cu2+), manganese (Mn2+), zinc (Zn2+) etc. could add antimicrobial properties against implant-related infections. Double substitutions of TCP containing couples of Cu2+/Sr2+ or Mn2+/Sr2+ ions are considered to be the most perspective based on the results of our study. We established that single phase Ca3−2x(MˊMˊˊ)x(PO4)2 solid solutions are formed only at x ≤ 0.286, where Mˊ and Mˊˊ—divalent metal ions, such as Zn2+, Mg2+, Cu2+, Mn2+, and that in case of double substitutions, the incorporation of Sr2+ ions allows one to extend the limit of solid solution due to the enlargement of the unit cell structure. We also reported that antimicrobial properties depend on the substitution ion occupation of Ca2+ crystal sites in the β-TCP structure. The combination of two different ions in the Ca5 position, on one side, and in the Ca1, Ca2, Ca3, and Ca4 positions, on another side, significantly boosts antimicrobial properties. In the present work, zinc-lithium (Zn-Li) biodegradable alloys were coated with double substituted Mn2+/Sr2+ β-TCP and double substituted Cu2+/ Sr2+ β-TCP, with the scope to promote osteoinductive effect (due to the Sr2+ presence) and to impart antimicrobial properties (thanks to Cu2+ or Mn2+ ions). The Pulsed Laser Deposition (PLD) method was applied as the coating's preparation technique. It was shown that films deposited using PLD present good adhesion strength and hardness and are characterized by a nanostructured background with random microparticles on the surface. For coatings characterization, Fourier Transform Infrared Spectroscopy, X-ray Diffraction, and Scanning Electron Microscopy coupled with Energy Dispersive X-ray and X-ray Photoelectron Spectroscopy were applied. The microbiology tests on the prepared coated Zn-Li alloys were performed with the Gram-positive (Staphylococcus aureus, Enterococcus faecalis) and Gram-negative (Salmonella typhimurium, Escherichia coli) bacteria strains and Candida albicans fungus. The antimicrobial activity tests showed that Mn2+/Sr2+ β-TCP -coated and Cu2+/Sr2+ β-TCP coated Zn-Li alloys were able to inhibit the growth of all five microorganisms. The prepared coatings are promising in improving the degradation behavior and biological properties of Zn-Li alloys, and further studies are necessary before a possible clinical translation

In order to evaluate the feasibility of zinc alloys as future biodegradable bone implant materials, the mechanical properties, corrosion resistance, hemocompatibility, cell activity, proliferation and adhesion, in vivo animal implantation experiments have been employed. The experimental results show that the alloying element magnesium, calcium and strontium can significantly improve the mechanical properties of pure zinc, and further deformation processes can further improve the mechanical properties of zinc alloys. Alloying elements can effectively control the corrosion rates of zinc alloys, which are between the rates of magnesium alloys and iron alloys. Zinc and zinc alloys exhibit excellent hemocompatibility and the hemolysis rate is far lower than 5%. After adding alloying elements Mg, Ca and Sr, MG63 and ECV304 cell proliferation rate and activity increased significantly, while for VSMC cell, the influence of alloying elements effect is not obvious. Zinc alloy intramedullary pins can effectively promote the new bone formation, and after 2 months implanted in mice femur, they still maintained a relatively complete structure, indicating that they are able to provide enough mechanical strength and thus more conducive to bone tissue repair and healing