Fixation of medial malleolar fractures with magnesium bioabsorbable headless compression screws: short-term clinical and radiological outcomes in eleven patients

A comparative study on the effects of biodegradable high-purity magnesium screw and polymer screw for fixation in epiphyseal trabecular bone

With mechanical strength close to cortical bone, biodegradable and osteopromotive properties, magnesium (Mg)-based implants are promising biomaterials for orthopedic applications. However, during the degradation of such implants, there are still concerns on the potential adverse effects such as formation of cavities, osteolytic phenomena and chronic inflammation. Therefore, to transform Mg-based implants into clinical practice, the present study evaluated the local effects of high-purity Mg screws (HP-Mg, 99.99 wt%) by comparing with clinically approved polylactic acid (PLA) screws in epiphyseal trabecular bone of rabbits. After implantation of screws at the rabbit distal femur, bone microstructural, histomorphometric and biomechanical properties were measured at various time points (weeks 4, 8 and 16) using micro-CT, histology and histomorphometry, micro-indentation and scanning electron microscope. HP-Mg screws promoted peri-implant bone ingrowth with higher bone mass (BV/TV at week 4: 0.189 ± 0.022 in PLA group versus 0.313 ± 0.053 in Mg group), higher biomechanical properties (hardness at week 4: 35.045 ± 1.000 HV in PLA group versus 51.975 ± 2.565 HV in Mg group), more mature osteocyte LCN architecture, accelerated bone remodeling process and alleviated immunoreactive score (IRS of Ram11 at week 4: 5.8 ± 0.712 in PLA group versus 3.75 ± 0.866 in Mg group) as compared to PLA screws. Furthermore, we conducted finite element analysis to validate the superiority of HP-Mg screws as orthopedic implants by demonstrating reduced stress concentration and uniform stress distribution around the bone tunnel, which led to lower risks of trabecular microfractures. In conclusion, HP-Mg screws demonstrated greater osteogenic bioactivity and limited inflammatory response compared to PLA screws in the epiphyseal trabecular bone of rabbits. Our findings have paved a promising way for the clinical application of Mg-based implants.

Peri-articular elbow fracture fixations with magnesium implants and a review of current literature: A case series

BACKGROUND

In recent years, the use of Magnesium alloy implants have gained renewed popularity, especially after the first commercially available Conformité Européenne approved Magnesium implant became available (MAGNEZIX® CS, Syntellix) in 2013.

AIM

To document our clinical and radiographical outcomes using magnesium implants in treating peri-articular elbow fractures.

METHODS

Our paper was based on a retrospective case series design. Intra-operatively, a standardized surgical technique was utilized for insertion of the magnesium implants. Post - operatively, clinic visits were standardized and physical exam findings, functional scores, and radiographs were obtained at each visit. All complications were recorded.

RESULTS

Five patients with 6 fractures were recruited (2 coronoid, 3 radial head and 1 capitellum). The mean patient age and length of follow up was 54.6 years and 11 months respectively. All fractures healed, and none exhibited loss of reduction or complications requiring revision surgery. No patient developed synovitis of the elbow joint or suffered electrolytic reactions when titanium implants were used concurrently.

CONCLUSION

Although there is still a paucity of literature available on the subject and further studies are required, magnesium implants appear to be a feasible tool for fixation of peri-articular elbow fractures with promising results in our series.

Mg-Zn-Ca Alloy (ZX00) Screws Are Resorbed at a Mean of 2.5 Years After Medial Malleolar Fracture Fixation: Follow-up of a First-in-humans Application and Insights From a Sheep Model

BACKGROUND

In the ongoing development of bioresorbable implants, there has been a particular focus on magnesium (Mg)-based alloys. Several Mg alloys have shown promising properties, including a lean, bioresorbable magnesium-zinc-calcium (Mg-Zn-Ca) alloy designated as ZX00. To our knowledge, this is the first clinically tested Mg-based alloy free from rare-earth elements or other elements. Its use in medial malleolar fractures has allowed for bone healing without requiring surgical removal. It is thus of interest to assess the resorption behavior of this novel bioresorbable implant.

QUESTIONS/PURPOSES

(1) What is the behavior of implanted Mg-alloy (ZX00) screws in terms of resorption (implant volume, implant surface, and gas volume) and bone response (histologic evaluation) in a sheep model after 13 months and 25 months? (2) What are the radiographic changes and clinical outcomes, including patient-reported outcome measures, at a mean of 2.5 years after Mg-alloy (ZX00) screw fixation in patients with medial malleolar fractures?

METHODS

A sheep model was used to assess 18 Mg-alloy (ZX00) different-length screws (29 mm, 24 mm, and 16 mm) implanted in the tibiae and compared with six titanium-alloy screws. Micro-CT was performed at 13 and 25 months to quantify the implant volume, implant surface, and gas volume at the implant sites, as well as histology at both timepoints. Between July 2018 and October 2019, we treated 20 patients with ZX00 screws for medial malleolar fractures in a first-in-humans study. We considered isolated, bimalleolar, or trimalleolar fractures potentially eligible. Thus, 20 patients were eligible for follow-up. However, 5% (one patient) of patients were excluded from the analysis because of an unplanned surgery for a pre-existing osteochondral lesion of the talus performed 17 months after ZX00 implantation. Additionally, another 5% (one patient) of patients were lost before reaching the minimum study follow-up period. Our required minimum follow-up period was 18 months to ensure sufficient time to observe the outcomes of interest. At this timepoint, 10% (two patients) of patients were either missing or lost to follow-up. The follow-up time was a mean of 2.5 ± 0.6 years and a median of 2.4 years (range 18 to 43 months).

RESULTS

In this sheep model, after 13 months, the 29-mm screws (initial volume: 198 ± 1 mm 3 ) degraded by 41% (116 ± 6 mm 3 , mean difference 82 [95% CI 71 to 92]; p < 0.001), and after 25 months by 65% (69 ± 7 mm 3 , mean difference 130 [95% CI 117 to 142]; p < 0.001). After 13 months, the 24-mm screws (initial volume: 174 ± 0.2 mm 3 ) degraded by 51% (86 ± 21 mm 3 , mean difference 88 [95% CI 52 to 123]; p = 0.004), and after 25 months by 72% (49 ± 25 mm 3 , mean difference 125 [95% CI 83 to 167]; p = 0.003). After 13 months, the 16-mm screws (initial volume: 112 ± 5 mm 3 ) degraded by 57% (49 ± 8 mm 3 , mean difference 63 [95% CI 50 to 76]; p < 0.001), and after 25 months by 61% (45 ± 10 mm 3 , mean difference 67 [95% CI 52 to 82]; p < 0.001). Histologic evaluation qualitatively showed ongoing resorption with new bone formation closely connected to the resorbing screw without an inflammatory reaction. In patients treated with Mg-alloy screws after a mean of 2.5 years, the implants were radiographically not visible in 17 of 18 patients and the bone had homogenous texture in 15 of 18 patients. No clinical or patient-reported complications were observed.

CONCLUSION

In this sheep model, Mg-alloy (ZX00) screws showed a resorption to one-third of the original volume after 25 months, without eliciting adverse immunologic reactions, supporting biocompatibility during this period. Mg-alloy (ZX00) implants were not detectable on radiographs after a mean of 2.5 years, suggesting full resorption, but further studies are needed to assess environmental changes regarding bone quality at the implantation site after implant resorption.

CLINICAL RELEVANCE

The study demonstrated successful healing of medial malleolar fractures using bioresorbable Mg-alloy screws without clinical complications or revision surgery, resulting in pain-free ankle function after 2.5 years. Future prospective studies with larger samples and extended follow-up periods are necessary to comprehensively assess the long-term effectiveness and safety of ZX00 screws, including an exploration of limitations when there is altered bone integrity, such as in those with osteoporosis. Additional use of advanced imaging techniques, such as high-resolution CT, can enhance evaluation accuracy.

Magnesium-based alloys with adapted interfaces for bone implants and tissue engineering

Magnesium and its alloys are one of the most used materials for bone implants and tissue engineering. They are characterized by numerous advantages such as biodegradability, high biocompatibility and mechanical properties with values close to the human bone. Unfortunately, the implant surface must be adequately tuned, or Mg-based alloys must be alloyed with other chemical elements due to their increased corrosion effect in physiological media. This article reviews the clinical challenges related to bone repair and regeneration, classifying bone defects and presenting some of the most used and modern therapies for bone injuries, such as Ilizarov or Masquelet techniques or stem cell treatments. The implant interface challenges are related to new bone formation and fracture healing, implant degradation and hydrogen release. A detailed analysis of mechanical properties during implant degradation is extensively described based on different literature studies that included in vitro and in vivo tests correlated with material properties' characterization. Mg-based trauma implants such as plates and screws, intramedullary nails, Herbert screws, spine cages, rings for joint treatment and regenerative scaffolds are presented, taking into consideration their manufacturing technology, the implant geometrical dimensions and shape, the type of in vivo or in vitro studies and fracture localization. Modern technologies that modify or adapt the Mg-based implant interfaces are described by presenting the main surface microstructural modifications, physical deposition and chemical conversion coatings. The last part of the article provides some recommendations from a translational perspective, identifies the challenges associated with Mg-based implants and presents some future opportunities. This review outlines the available literature on trauma and regenerative bone implants and describes the main techniques used to control the alloy corrosion rate and the cellular environment of the implant.

Magnesium implant degradation provides immunomodulatory and proangiogenic effects and attenuates peri-implant fibrosis in soft tissues

Implants made of magnesium (Mg) are increasingly employed in patients to achieve osteosynthesis while degrading in situ. Since Mg implants and Mg²⁺ have been suggested to possess anti-inflammatory properties, the clinically observed soft tissue inflammation around Mg implants is enigmatic. Here, using a rat soft tissue model and a 1-28 d observation period, we determined the temporo-spatial cell distribution and behavior in relation to sequential changes of pure Mg implant surface properties and Mg²⁺ release. Compared to nondegradable titanium (Ti) implants, Mg degradation exacerbated initial inflammation. Release of Mg degradation products at the tissue-implant interface, culminating at 3 d, actively initiated chemotaxis and upregulated mRNA and protein immunomodulatory markers, particularly inducible nitric oxide synthase and toll-like receptor-4 up to 6 d, yet without a cytotoxic effect. Increased vascularization was demonstrated morphologically, preceded by high expression of vascular endothelial growth factor. The transition to appropriate tissue repair coincided with implant surface enrichment of Ca and P and reduced peri-implant Mg²⁺ concentration. Mg implants revealed a thinner fibrous encapsulation compared with Ti. The detailed understanding of the relationship between Mg material properties and the spatial and time-resolved cellular processes provides a basis for the interpretation of clinical observations and future tailoring of Mg implants.

In Vitro and In Vivo Applications of Magnesium-Enriched Biomaterials for Vascularized Osteogenesis in Bone Tissue Engineering: A Review of Literature

Bone is a highly vascularized tissue, and the ability of magnesium (Mg) to promote osteogenesis and angiogenesis has been widely studied. The aim of bone tissue engineering is to repair bone tissue defects and restore its normal function. Various Mg-enriched materials that can promote angiogenesis and osteogenesis have been made. Here, we introduce several types of orthopedic clinical uses of Mg; recent advances in the study of metal materials releasing Mg ions (pure Mg, Mg alloy, coated Mg, Mg-rich composite, ceramic, and hydrogel) are reviewed. Most studies suggest that Mg can enhance vascularized osteogenesis in bone defect areas. Additionally, we summarized some research on the mechanisms related to vascularized osteogenesis. In addition, the experimental strategies for the research of Mg-enriched materials in the future are put forward, in which clarifying the specific mechanism of promoting angiogenesis is the crux.

Magnesium-Based Temporary Implants: Potential, Current Status, Applications, and Challenges

Biomedical implants are important devices used for the repair or replacement of damaged or diseased tissues or organs. The success of implantation depends on various factors, such as mechanical properties, biocompatibility, and biodegradability of the materials used. Recently, magnesium (Mg)-based materials have emerged as a promising class of temporary implants due to their remarkable properties, such as strength, biocompatibility, biodegradability, and bioactivity. This review article aims to provide a comprehensive overview of current research works summarizing the above-mentioned properties of Mg-based materials for use as temporary implants. The key findings from in-vitro, in-vivo, and clinical trials are also discussed. Further, the potential applications of Mg-based implants and the applicable fabrication methods are also reviewed.

High Complication Rate and High Percentage of Regressing Radiolucency in Magnesium Screw Fixation in 18 Consecutive Patients

(1) Background: Magnesium-based implants use has become a research focus in recent years. Radiolucent areas around inserted screws are still worrisome. The objective of this study was to investigate the first 18 patients treated using MAGNEZIX^® CS screws. (2) Methods: This retrospective case series included all 18 consecutive patients treated using MAGNEZIX^® CS screws at our Level-1 trauma center. Radiographs were taken at 3-, 6- and 9-month follow-ups. Osteolysis, radiolucency and material failure were assessed, as were infection and revision surgery. (3) Results: Most patients (61.1%) had surgery in the shoulder region. Radiolucency regressed from 55.6% at 3-month follow-ups to 11.1% at 9-month follow-ups. Material failure occurred in four patients (22.22%) and infection occurred in two patients, yielding a 33.33% complication rate. (4) Conclusion: MAGNEZIX^® CS screws demonstrated a high percentage of radiolucency that regressed and seems to be clinically irrelevant. The material failure rate and infection rate require further research.

Resorbable magnesium screws for fixation of medial epicondyle avulsion fractures in skeletally immature patients: A comparison with Kirschner wires

BACKGROUND

Displaced medial epicondyle fractures are treated with open reduction and internal fixation with K-wires or screws. Rates of implant prominence, failure, or non-union reported are considerable. Magnesium screws have demonstrated biocompatibility, osteoconductivity, and high pull-out strength. The aim of this study was to compare surgical fixation of medial epicondyle fracture using resorbable magnesium Herbert screws to K-wires, in skeletally immature patients.

METHODS

A retrospective analysis was performed from January 2015 to April 2020. Inclusion criteria were as follows displaced medial epicondyle fracture, <15 years, and absence of concomitant ipsilateral upper limb fractures. Two consecutive cohorts based on fixation device were made: Group A (wires) and Group B (magnesium screws). Alignment, pain, range of motion, Mayo Elbow Performance Score, and radiological healing were assessed.

RESULTS

A total of 27 patients were included: 15 in Group A and 12 in Group B. Groups were comparable for age and sex. Mean follow-up was higher in Group A (38.73 ± 3.15 vs 26.18 ± 4.85 months; p < 0.001). No significant differences were observed regarding range of motion, alignment, pain, and Mayo Elbow Performance Score, with excellent results in both groups. Two patients in Group A developed a deep wound pin site infection requiring antibiotics. X-rays revealed three cases of non-union in Group A and one in Group B, all of them asymptomatic. No patient required a second surgical procedure.

CONCLUSION

Open reduction and internal fixation of medial epicondyle fractures with magnesium screws showed comparable results to a widely accepted procedure such as the use of K-wires, potentially with a lower incidence of non-union and infection. No adverse reactions were recorded.

LEVEL OF EVIDENCE

level III.

Osteotomy after medial malleolus fracture fixed with magnesium screws ZX00 - A case report

Magnesium alloys have recently become the focus of research, as these implants exhibit suitable biocompatibility and appropriate mechanical properties (Grün et al., 2018 [1]). Through intensive preclinical and clinical investigation, many questions regarding stability, biocompatibility and degradation behavior have been answered (Holweg et al., 2020 [2]). This case report aims to describe handling of these implants in a revision situation, especially when located in situ. To describe available options and relevant considerations, including planning and implementation, a revision surgery of a healed medial malleolus fracture is presented. A medial malleolus fracture was primarily treated by a trauma surgeon with two magnesium screws. Due to an osteochondral lesion of the talus, a revision surgery with osteotomy of the medial malleolus was necessary after 17 months. In this revision, conventional screw removal was not possible due to the degradation of the implant. Taking the degradation and the yield strength of the implant into account, we have chosen on the one hand to over-drill and on the other to leave and perforate the screw. To the best of our knowledge, this is the first case study focusing on the clinical intraoperative site of human bone stabilized with magnesium screws. Despite the hydrogen gas production that occurs during degradation, a solid bone-to-implant interface was evident. With this report, we want to encourage the surgical user to get more involved with resorbable magnesium implants.

New and innovative biomaterials, techniques and therapy concepts: Biologization in maxillofacial surgery, oral surgery and dentistry is in full swing. PRF, PRGF, PRP, blood plasma-stabilized augmentations, supplementation of micronutrients and vitamins - what opportunities do such "biological" approaches actually offer? We introduce them here

Biomaterials of natural origin have recently gained increasing attention in the field of dental implantology. The requirements for such materials, however, are very high. In addition to high clinical efficiency in tissue regeneration, wound healing should be demonstrably positively influenced. The translational division for regenerative orofacial medicine of the Clinic and Polyclinic for Oral and Maxillofacial Surgery of the University Medical Center Hamburg-Eppendorf (UKE) is examining this research topic by investigating which innovative treatment methods for the reconstruction of bone defects or for augmentative procedures can be applied in the future or are already being applied in the field of oral and maxillofacial surgery.

Magnesium implants in orthopaedic surgery create a diagnostic conundrum: A radiology case series and literature review

During a routine post-operative orthopaedic radiograph reading session, repeated unusual radiographic soft tissue and bone appearances became evident. It was discovered that these patients had received biodegradable magnesium implants which have recently been introduced into orthopaedic clinical practice. To the untrained eye, the combination of peri-metallic bone resorption with associated soft tissue gas, could easily be mistaken for post-operative infection. The aim of this study is to properly characterise the radiographic post-operative appearances of biodegradable magnesium orthopaedic hardware. We retrospectively evaluated radiographs of all patients who underwent magnesium screw implantation for fractures over a 6 month period. Four patients, mean age of 9.75 (range: 6-15) years who underwent magnesium screw fixation following fracture were included in the study. Follow up duration was 100 days (range: 75-122) with a mean of 2.5 postoperative radiographs being performed per patient during this period. All cases demonstrated post-operative peri-metallic radiolucency which developed around the magnesium screws on x-ray, which subsequently resorbed over time. Peri-metallic soft tissue gas was observed in all patients. In two cases, magnesium implants fractured. As the use of biodegradable metal implants becomes more common, it is important for radiologists to be aware of their imaging characteristics. Prior to reporting a case, it would be prudent to know if biodegradable screws have been utilised and whether there exists a clinical concern for post-operative infection in patients with these particular implants, in which case it would be critical not to dismiss peri-prosthetic radiolucencies and soft tissue gas as merely a sequela of the natural metal degradation process.

Making Hardware Removal Unnecessary by Using Resorbable Implants for Osteosynthesis in Children

Introduction: Following osteosynthesis, children generally require a second surgery to remove the hardware. This becomes unnecessary, by using resorbable implants. Limiting the number of required surgeries and their associated risks, this technique provides critical aspects of minimally invasive surgery. This review focuses on resorbable implants for osteosynthesis for the treatment of fractures in children and discusses their clinical features. Method: We provide an overview of the two most common technologies used in resorbable osteosynthesis materials: polymer- and magnesium-based alloys. Clinical examples of osteosynthesis are presented using polymer-based ActivaTM products and magnesium-based Magnezix^® products. Results: Polymer-based implants demonstrate surgical safety and efficacy. Due to their elasticity, initial placement of polymer-based products may demonstrate technical challenges. However, stability is maintained over the course of healing. While maintaining good biocompatibility, the rate of polymer-resorption may be controlled by varying the composition of polyesters and copolymers. Similarly, magnesium-based implants demonstrate good mechanical stability and resorption rates, while these characteristics may be controlled by varying alloy components. One of the significant shortcomings of magnesium is that metabolism results in the production of hydrogen gas. Both technologies provide equally good results clinically and radiographically, when compared to non-resorbable implants. Conclusion: Resorbable osteosynthesis materials demonstrate similar therapeutic results as conventional materials for osteosynthesis. Resorbable implants may have the potential to improve patient outcomes, by sparing children a second surgery for hardware removal.

Is the magnesium screw as stable as the titanium screw in the fixation of first metatarsal distal chevron osteotomy? A comparative biomechanical study on sawbones models

Background: Distal chevron osteotomy (DCO) is commonly performed in hallux valgus surgery. The fixation of the osteotomy is provided by various implants. The usage of biodegradable implants such as magnesium is gradually increasing due to the advantages they provide. In this study, we aimed to compare the fixation of DCO with magnesium or titanium screw biomechanically. Methods: Twenty sawbones were used. The samples were divided into two equal groups, including ten sawbones for fixation with single headless titanium (group-1) or magnesium screw (group-2). DCO and screw fixations were performed on all samples using the same technique. Biomechanical testing was applied to five samples in each group in cantilever and the other five in a physiological configuration using a computer connected to the electromechanical test machine. The obtained data were evaluated using the Shapiro-Wilk test, Student's t-test and Mann-Whitney U test on the IBM® SPSS (Statistical Package for the Social Sciences) V22.0 software. Significance was accepted at the p < 0.05 level. Results: There was no statistically significant difference between the magnesium screw and the titanium screw in terms of maximum force, maximum displacement and stiffness measurements in cantilever and physiological loadings (p > 0.05 for all). Conclusion: This study found no significant difference in biomechanical stability between the magnesium and titanium screws in DCO fixation on sawbones. Further studies with real bones are needed.

Can Hardware Removal be Avoided Using Bioresorbable Mg-Zn-Ca Screws After Medial Malleolar Fracture Fixation? Mid-Term Results of a First-In-Human Study

Ankle is the most common site of hardware removal, mainly performed within 12 months of the primary surgery. The prominence of the metallic hardware is a frequent cause of pain after fracture fixation. Over the last decade, the development of bioresorbable materials based on magnesium (Mg) has increased. Bioresorbable metals aim to avoid a second surgery for hardware removal.

METHODS

Twenty patients with isolated, bimalleolar, or trimalleolar ankle fractures were treated with bioresorbable screws made of Mg, 0.45wt% calcium (Ca) and 0.45wt% zinc (Zn) (ZX00). Patient-reported outcome measures (PROMs) including visual analogue scale (VAS) for pain, the presence of complications 6 and 12 months after surgery and the AOFAS scale after 12 months were reported. The functional outcomes were analysed through the range of motion (ROM) of the ankle joint with a standard goniometer. Degradation products and the bioresorbability of the screws were evaluated using plane radiographs.

RESULTS

One patient was lost to follow-up. All patients were free of pain, no complications, shoe conflict or misalignement were reported after 12 months of follow-up. No Mg screws were surgically removed. An additional fixation of the distal fibula or the dorsal tibial fragment with conventional titanium implants (Ti) was performed in 17 patients. Within 12 months after primary refixation, 12 of these patients (71%) underwent a second surgery for Ti hardware removal. The mean AOFAS score was 89.8±7.1 and the difference between the treated and the non-treated site in the ROM of the talocrural joint was 2°±11° after 12 months. Radiolucent areas around the screws were attributed to degradation and did not affect clinical or functional outcomes. After one year, the Mg screw heads could not be detected in the plane radiographs of 17 patients which suggests that the majority of the screw head is degraded without introducing adverse reactions.

CONCLUSIONS

At 6 and 12 months, the bioresorbable Mg screws show excellent PROMs without complications or need for screw removal. The resorbability of the screw heads in most of the patients after one year could also provide an advantage over conventional bio-inert implants by avoiding related skin irritation due for instance to shoe conflict.

Magnesium-Based Alloys Used in Orthopedic Surgery

Magnesium (Mg)-based alloys have become an important category of materials that is attracting more and more attention due to their high potential use as orthopedic temporary implants. These alloys are a viable alternative to nondegradable metals implants in orthopedics. In this paper, a detailed overview covering alloy development and manufacturing techniques is described. Further, important attributes for Mg-based alloys involved in orthopedic implants fabrication, physiological and toxicological effects of each alloying element, mechanical properties, osteogenesis, and angiogenesis of Mg are presented. A section detailing the main biocompatible Mg-based alloys, with examples of mechanical properties, degradation behavior, and cytotoxicity tests related to in vitro experiments, is also provided. Special attention is given to animal testing, and the clinical translation is also reviewed, focusing on the main clinical cases that were conducted under human use approval.

Biodegradable magnesium alloy WE43 porous scaffolds fabricated by laser powder bed fusion for orthopedic applications: Process optimization, in vitro and in vivo investigation

Laser powder bed fusion (L-PBF) of magnesium (Mg) alloy porous scaffolds is expected to solve the dual challenges from customized structures and biodegradable functions required for repairing bone defects. However, one of the key technical difficulties lies in the poor L-PBF process performance of Mg, contributed by the high susceptibility to oxidation, vaporization, thermal expansion, and powder attachment etc. This work investigated the influence of L-PBF energy input and scanning strategy on the formation quality of porous scaffolds by using WE43 powder, and characterized the microstructure, mechanical properties, biocompatibility, biodegradation and osteogenic effect of the as-built WE43 porous scaffolds. With the customized energy input and scanning strategy, the relative density of struts reached over 99.5%, and the geometrical error between the designed and the fabricated porosity declined to below 10%. Massive secondary phases including intermetallic precipitates and oxides were observed. The compressive strength (4.37–23.49 MPa) and elastic modulus (154.40–873.02 MPa) were comparable to those of cancellous bone. Good biocompatibility was observed by in vitro cell viability and in vivo implantation. The biodegradation of as-built porous scaffolds promoted the osteogenic effect, but the structural integrity devastated after 12 h by the immersion tests in Hank's solution and after 4 weeks by the implantation in rabbits' femur, indicating an excessively rapid degradation rate.

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In vitro and in vivo investigations were performed on WE43 porous scaffolds.

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Reliable fusion quality and dimensional accuracy were achieved.

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The compressive strength and Young modulus ranged 4.37–23.49 and 154.40–873.02 MPa.

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Good biocompatibility and improved osteogenic effect were observed.

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The massive secondary phases as well as the enlarged specific surface resulted to a rapid degradation rate.

Dynamic in vivo monitoring of fracture healing process in response to magnesium implant with multimodal imaging: Pilot longitudinal study in a rat external fixation model

Rodent models are commonly used in pre-clinical research of magnesium (Mg) -based and other types of biomaterials for fracture treatment. Most studies selected unstable fixation methods, and there is a...

Fixation of Unstable Osteochondritis Dissecans Lesions and Displaced Osteochondral Fragments Using New Biodegradable Magnesium Pins in Adolescents

OBJECTIVE

Fixation of unstable osteochondritis dissecans (OCD) lesions and displaced osteochondral fragments are frequently performed procedures in pediatric orthopedic surgery. Since 2018, CE-certified MAGNEZIX pins are used in our institution in these cases. The aim of this study was (1) to analyze safety, efficiency, and limitations of magnesium-pin-based fixation of unstable OCD lesions and displaced osteochondral fragments and (2) to report clinical and radiological outcomes at short-term follow-up (FU).

DESIGN

In this prospective cohort study, 19 patients (10 girls and 9 boys) were included. Inclusion criteria were (1) magnetic resonance imaging-confirmed unstable OCD lesion or displaced osteochondral fragment, (2) fixation with magnesium-based pins, and (3) minimum FU of 6 months. X-rays were taken 6 weeks and 6 months after operation and magnetic resonance imaging scans every 4 to 6 months to assess the healing progress.

RESULTS

In total 67 pins were used, with a mean of 3.6 ± 1.4 per patient. Average age at surgery was 13.7 years (11-17 years). Mean time of operation was 56 ± 31 minutes, including arthroscopy, fixation, and patellar realignment (n = 6). No intraoperative complications occurred. Average FU was 11.3 ± 4.2 months (6-20 months). No redislocation or new dislocation occurred. Until now a complete radiographic healing occurred in 12 cases. Due to an implant failure in one case 11 weeks after the index surgery a revision became necessary.

CONCLUSIONS

In short-term FU of 11 ± 4 months MAGNEZIX pins provide high stability after fixation of unstable OCDs and displaced osteochondral fragments leading to uncomplicated and timely healing.

Use of biomaterials in scaphoid fracture fixation, a systematic review

BACKGROUND

Scaphoid fractures account for 60-70% carpal injury. Due to limited vascular supply achieving adequate reduction and healing is important to avoid complications including avascular necrosis. Recent technological advances have led to renewed vigour in bioabsorbable material research to develop devices which could be used without the need for removal and complications including stress shielding and suboptimal imaging.

METHODS

A systematic search of databases including PubMed, Ovid Medline, and Google Scholar databases was made to identify studies related to the use of bioabsorbable materials in scaphoid fixation and postoperative patient outcomes. PRISMA guidelines were utilised for this review.

FINDINGS

Initial search results yielded 852 studies. 124 studies were screened, with 79 patients across 7 studies included in this review. Poly-L-Lactic acid derivatives were the most common biomaterial for scaphoid fixation, with magnesium and polyglycolide also used. Levels of evidence for studies ranged between III-IV. Analysis demonstrated mixed findings with generally comparable outcomes to conventional alloy-based screws.

INTERPRETATION

Development in bioabsorbable materials is ongoing, however there remains a dearth in data regarding their use in the scaphoid. Further research is needed to establish the efficacy and applicability of bioabsorbable devices in the scaphoid bone.

A review of the physiological impact of rare earth elements and their uses in biomedical Mg alloys

Magnesium (Mg) is well-tolerated by the body, displaying exceedingly low toxicity, rapid excretion, and numerous bioactive effects, including improved bone formation and protection against oxidative stresses; further, Mg alloys can be degraded in vivo to allow complete removal of an implant without surgical intervention, avoiding revision surgery and thrombosis concerns seen with permanent implants. Rare earth elements (REEs) have been of particular interest in alloying Mg alloys for nearly a century due to their unique chemical and physical properties but have attracted increasing attention in recent decades. The REEs contribute greatly to the mechanical and biological properties of metal alloys, and so are common in Mg alloys in a wide variety of applications; in particular, they represent the dominant alloying additions in current, clinically applied Mg alloys. Notably, the use of these elements may assist in the development of advanced Mg alloys for use as biodegradable orthopedic implants and cardiovascular stents. To this end, current research progress in this area, highlighting the physiological impact of REEs in Mg alloys, is reviewed. Clinical work and preclinical data of REE-containing Mg alloys are analyzed. The biological roles of REEs in cellular responses in vivo require further research in the development of biofunctional Mg alloy medical devices. STATEMENT OF SIGNIFICANCE: The presented work is a review into the biological impact and current application of rare-earth elements (REEs) in biodegradable Mg-based biomaterials. Despite their efficacy in improving corrosion, mechanical, and manufacturability properties of Mg alloys, the physiological effects of REEs remain poorly understood. Therefore, the present work was undertaken to both provide guidance in the development of new biomedical alloys, and highlight areas of existing concerns and unclear knowledge. Key findings of this review include a summary of current clinical and preclinical work, and the identification of Sc as the most promising REE with regards to physiological impact. Y, Ce, Pr, Gd, Dy, Yb, Sm, and Eu should be considered carefully before their use as alloying elements, with other REEs intermediate or insufficiently studied.

Zn-0.8Mg-0.2Sr (wt.%) Absorbable Screws-An In-Vivo Biocompatibility and Degradation Pilot Study on a Rabbit Model

In this pilot study, we investigated the biocompatibility and degradation rate of an extruded Zn-0.8Mg-0.2Sr (wt.%) alloy on a rabbit model. An alloy screw was implanted into one of the tibiae of New Zealand White rabbits. After 120 days, the animals were euthanized. Evaluation included clinical assessment, microCT, histological examination of implants, analyses of the adjacent bone, and assessment of zinc, magnesium, and strontium in vital organs (liver, kidneys, brain). The bone sections with the implanted screw were examined via scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). This method showed that the implant was covered by a thin layer of phosphate-based solid corrosion products with a thickness ranging between 4 and 5 µm. Only negligible changes of the implant volume and area were observed. The degradation was not connected with gas evolution. The screws were fibrointegrated, partially osseointegrated histologically. We observed no inflammatory reaction or bone resorption. Periosteal apposition and formation of new bone with a regular structure were frequently observed near the implant surface. The histological evaluation of the liver, kidneys, and brain showed no toxic changes. The levels of Zn, Mg, and Sr after 120 days in the liver, kidneys, and brain did not exceed the reference values for these elements. The alloy was safe, biocompatible, and well-tolerated.

Use of resorbable magnesium screws in children: systematic review of the literature and short-term follow-up from our series

PURPOSE

Biodegradable implants are of major interest in orthopaedics, especially in the skeletally immature population. Magnesium (Mg) implants are promising for selected surgical procedure in adults, but evidence is lacking. Thus, the aim of this study is to analyze the safety and efficacy of resorbable Mg screw in different orthopaedic procedures in skeletally immature patients. In addition, we present a systematic review of the current literature on the clinical use of Mg implants.

METHODS

From 2018 until the writing of this manuscript, consecutive orthopaedic surgical procedures involving the use of Mg screws performed at our centre in patients < 15 years of age were retrospectively reviewed. In addition, a systematic review of the literature was performed in the main databases. We included clinical studies conducted on humans, using Mg-alloy implants for orthopaedic procedures.

RESULTS

A total of 14 patients were included in this retrospective analysis. Mean age at surgery was 10.8 years (sd 2.4), mean follow-up was 13.8 months (sd 7.5). Healing was achieved in all the procedures, with no implant-related adverse reaction. No patients required any second surgical procedure. The systematic review evidenced 20 clinical studies, 19 of which conducted on an adult and one including paediatric patients.

CONCLUSION

Evidence on resorbable Mg implants is low but promising in adults and nearly absent in children. Our series included apophyseal avulsion, epiphyseal fractures, osteochondritis dissecans, displaced osteochondral fragment and tendon-to-bone fixation. Mg screws guaranteed stable fixation, without implant failure, with good clinical and radiological results and no adverse events.

LEVEL OF EVIDENCE

IV - Single cohort retrospective analysis with systematic review.

Research status of biodegradable metals designed for oral and maxillofacial applications: A review

The oral and maxillofacial regions have complex anatomical structures and different tissue types, which have vital health and aesthetic functions. Biodegradable metals (BMs) is a promising bioactive materials to treat oral and maxillofacial diseases. This review summarizes the research status and future research directions of BMs for oral and maxillofacial applications. Mg-based BMs and Zn-based BMs for bone fracture fixation systems, and guided bone regeneration (GBR) membranes, are discussed in detail. Zn-based BMs with a moderate degradation rate and superior mechanical properties for GBR membranes show great potential for clinical translation. Fe-based BMs have a relatively low degradation rate and insoluble degradation products, which greatly limit their application and clinical translation. Furthermore, we proposed potential future research directions for BMs in the oral and maxillofacial regions, including 3D printed BM bone scaffolds, surface modification for BMs GBR membranes, and BMs containing hydrogels for cartilage regeneration, soft tissue regeneration, and nerve regeneration. Taken together, the progress made in the development of BMs in oral and maxillofacial regions has laid a foundation for further clinical translation.

Bioresorbable Magnesium-Based Alloys as Novel Biomaterials in Oral Bone Regeneration: General Review and Clinical Perspectives

Bone preservation and primary regeneration is a daily challenge in the field of dental medicine. In recent years, bioresorbable metals based on magnesium (Mg) have been widely investigated due to their bone-like modulus of elasticity, their high biocompatibility, antimicrobial, and osteoconductive properties. Synthetic Mg-based biomaterials are promising candidates for bone regeneration in comparison with other currently available pure synthetic materials. Different alloys based on Mg were developed to fit clinical requirements. In parallel, advances in additive manufacturing offer the possibility to fabricate experimentally bioresorbable metallic porous scaffolds. This review describes the promising clinical results of resorbable Mg-based biomaterials for bone repair in osteosynthetic application and discusses the perspectives of use in oral bone regeneration.

Effectiveness and safety of biodegradable Mg-Nd-Zn-Zr alloy screws for the treatment of medial malleolar fractures

Background

/Objective: This study aimed to evaluate the effectiveness and safety of treating medial malleolar fractures using our patented Mg-Nd-Zn-Zr alloy (abbr. JDBM) screws with Ca–P coating, in order to provide a solid basis for their further clinical translation.

Methods

Nine patients with medial malleolar fractures were treated using coated JDBM screws. All patients had closed injuries, and none had open fractures. Postoperative radiography was performed to evaluate fracture healing and degradation of the JDBM screws. The visual analogue scale (VAS) was used to evaluate the degree of 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. Postoperative complications, including infection, failure of internal fixation, and malunion, were carefully recorded during follow-up.

Results

The mean follow-up time was 12.2 ​± ​4.9 months. After the operation, all patients achieved good medial malleolar fracture alignment, and none of them experienced breakage of the JDBM screws before fracture healing. Postoperative radiography indicated JDBM screws gradually degradated with implantation time, and obvious degradation could be observed 12 months, postoperatively. At the final follow-up, the patients’ mean VAS score was 2.3 ​± ​1.9. The mean AOFAS score was 90.4 ​± ​8.9, with excellent or good rates of 88.9%. None of the patients experienced infection, failure of internal fixation, malunion, or other complications.

Conclusion

Coated biodegradable JDBM screws are effective for the treatment of medial malleolar fractures, and have good prospects for further clinical translation in the future.

Translational potential statement

The results of this study indicates coated biodegradable JDBM screw is an alternative internal fixation instrument for fracture treatment and has excellent prospects for clinical translation.

[Research progress in diagnosis and treatment of distal tibiofibular syndesmosis injury]

Objective

To review the research progress in the diagnosis and treatment of distal tibiofibular syndesmosis injury.

Methods

The recent literature about distal tibiofibular syndesmosis injury was reviewed and analyzed.

Results

Distal tibiofibular syndesmosis injury is commonly seen in ankle joint injury, the anatomical complexities make diagnosis and treatment difficult. Preoperative physical examination, radiologic evaluation, and intraoperative stress-testing are important for the diagnosis. Aggressive treatment is also recommended for these injuries to prevent long-term chronic instability. Internal fixation is the main treatment, including metal screw, degradable screw, elastic fixation, and hybrid techniques. Metal screw fixation is still the current mainstream, but elastic fixation represented by Suture-button is more in line with the physiological characteristics of ankle joint, and the rate of secondary operation is low while the clinical outcome is satisfactory. The application prospect of elastic fixation is worthy of expectation.

Conclusion

It's crucial for patient with ankle fracture to repair the distal tibiofibular syndesmosis injury. How to diagnose the injury more accurately and simply, how to increase the success rate of reduction, and how to reduce the complications of surgery are still worthy for further exploration.

A lean magnesium-zinc-calcium alloy ZX00 used for bone fracture stabilization in a large growing-animal model

Over the last decade, demand has increased for developing new, alternative materials in pediatric trauma care to overcome the disadvantages associated with conventional implant materials. Magnesium (Mg)-based alloys seem to adequately fulfill the vision of a homogeneously resorbable, biocompatible, load-bearing and functionally supportive implant. The aim of the present study is to introduce the high-strength, lean alloy Mg‒0.45Zn‒0.45Ca, in wt% (ZX00), and for the first time investigate the clinical applicability of screw osteosynthesis using this alloy that contains no rare-earth elements. The alloy was applied in a growing sheep model with osteotomized bone (simulating a fracture) and compared to a non-osteotomy control group regarding degradation behavior and fracture healing. The alloy exhibits an ultimate tensile strength of 285.7 ± 3.1 MPa, an elongation at fracture of 18.2 ± 2.1%, and a reduced in vitro degradation rate compared to alloys containing higher amounts of Zn. In vivo, no significant difference between the osteotomized bone and the control group was found regarding the change in screw volume over implantation time. Therefore, it can be concluded that the fracture healing process, including its effects on the surrounding area, has no significant influence on degradation behavior. There was also no negative influence from hydrogen-gas formation on fracture healing. Despite the proximal and distal screws showing chronologically different gas release, the osteotomy showed complete consolidation. STATEMENT OF SIGNIFICANCE: Conventional implants involve several disadvantages in pediatric trauma care. Magnesium-based alloys seem to overcome these issues as discussed in the recent literature. This study evaluates the clinical applicability of high-strength lean Mg‒0.45Zn‒0.45Ca (ZX00) screws in a growing-sheep model. Two groups, one including a simulated fracture and one group without fracture, underwent implantation of the alloy and were compared to each other. No significant difference regarding screw volume was observed between the groups. There was no negative influence of hydrogen-gas formation on fracture healing and a complete fracture consolidation was found after 12 weeks for all animals investigated.

A lean bioabsorbable magnesium-zinc-calcium alloy ZX00 used for operative treatment of medial malleolus fractures: early clinical results of a prospective non-randomized first in man study

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.

Bioabsorbable magnesium screw versus conventional titanium screw fixation for medial malleolar fractures

Background

It is still unknown whether bioabsorbable magnesium (Mg) screws provide an advantage over titanium screws in the treatment of medial malleolar (MM) fractures. The purpose of this retrospective study is to compare the clinical and radiological outcomes of MM fractures fixed with either bioabsorbable Mg screws or conventional titanium screws.

Materials and methods

A cohort of 48 patients with MM fractures who underwent compression screw fixation was retrospectively reviewed. Twenty-three patients (16 male, 7 female; mean age: 37.9 ± 17.7 years) were treated with bioabsorbable Mg screws, and 25 patients (14 male, 11 female; mean age: 45.0 ± 15.7 years) were treated with conventional titanium screw fixation. All patients were followed up for at least 1 year, with a mean time of 24.6 ± 10.5 months (12–53 months). The American Orthopedic Foot and Ankle Society (AOFAS) scale was used to evaluate the clinical results. The Kellgren–Lawrence (KL) osteoarthritis grading was used to evaluate posttraumatic osteoarthritis on final ankle radiographs. Fracture union, rate of implant removal, and complications were recorded. Comparative analysis of two independent groups was performed using the chi-squared test and the Mann–Whitney U-test.

Results

The two groups were comparable concerning demographic and clinical characteristics. Age (p = 0.146), sex (p = 0.252), side (p = 0.190), MM fracture type (p = 0.500), associated fractures (p = 0.470), and follow-up period (p = 0.903) were similar between the groups. At final follow-up examination, AOFAS score (p = 0.191) was similar between groups. Fracture union was achieved in all cases. Grade of posttraumatic osteoarthritis, according to KL, was equally distributed in both groups (p = 0.074). No deep infection or osteomyelitis was seen. Five patients in the titanium screw group underwent implant removal, due to pain in three of them and difficulty in wearing shoes in the other two (p = 0.031). Implant removal was performed after a mean of 14.2 ± 3.1 months (12–19 months).

Conclusions

Bioabsorbable Mg and titanium screws had similar therapeutic efficacy in MM fracture fixation regarding functional and radiological outcomes. However, the rate of implant removal was higher with titanium screws. Bioabsorbable Mg screws may be a favorable fixation option since secondary implant removal procedures can be prevented.

Level of evidence

Level IV, Retrospective case series.

Magnesium Bioabsorbable Screw Fixation of Radial Styloid Fractures: Case Report

Background  Several types of fixation materials may be used for the radial styloid fractures such as Kirschner wire fixation, screw fixation, volar plate fixation, and fragment-specific radial buttress plate fixation. However, each of these fixation techniques has certain complications usually related to either the surgical dissection or the application of fixation and symptomatic permanent hardware. Implant removal secondary to irritation of prominent screw heads or bulky plates is not uncommon after radial styloid fracture fixation. Case Description  Herein, two patients with an isolated radial styloid fracture who were treated with bioabsorbable magnesium (alloy: MgYREZr) screws are presented. In both patients, the fracture union was achieved without any complication and need for implant removal. Literature Review  This is the first report on the use of magnesium screws for this indication. Clinical Relevance  Magnesium bioabsorbable compression screw fixation may be an alternative solution that eliminates removal operations due to symptomatic hardware in radial styloid fractures.

Osteosynthesis of the Mandibular Condyle With Magnesium-Based Biodegradable Headless Compression Screws Show Good Clinical Results During a 1-Year Follow-Up Period

PURPOSE

The use of titanium-based implants in mandibular condyle fractures can require implant removal because of screw penetration through the condylar surface. The use of biodegradable implants can avoid a second operation for implant removal and the associated possible complications. We investigated the clinical and radiologic outcomes of osteosynthesis of mandibular condyle fractures (MCFs) with biodegradable magnesium-based compression screws.

MATERIALS AND METHODS

We performed a retrospective observational study of 6 patients who had been treated at our department. We recorded the changes in jaw movements over time, occlusion, and possible complications at defined intervals of 1, 3, 6, and 12 months postoperatively. We also compared the preoperative computed tomography (CT) scans with the postoperative cone-beam CT (CBCT) scans at 6 and 12 months postoperatively to evaluate mandibular condyle healing and screw degradation.

RESULTS

Of the 6 patients, 4 were men and 2 were women, with a mean age of 43.2 years (range, 30 to 66 years). All 6 patients had unilateral MCFs. All the patients showed well-restored function of the temporomandibular joint with significant improvement in mouth opening (46.17 ± 6.49 mm), right (10.67 ± 1.03 mm) and left (10.67 ± 1.97 mm) laterotrusion, and protrusion (10.17 ± 1.33 mm) distances to physiologic values. The CBCT scans showed the remodeling processes of the mandibular condyle and a few radiolucencies indicating the magnesium-based screws. Although penetration of 1 screw tip through the condylar surface had occurred, no implant removal was necessary owing to biodegradation of the implant.

CONCLUSIONS

The results of the present study have shown that biodegradable magnesium-based compression screws provide good clinical results and avoid implant removal.

Comparison of SCAphoid fracture osteosynthesis by MAGnesium-based headless Herbert screws with titanium Herbert screws: protocol for the randomized controlled SCAMAG clinical trial

Background

Scaphoid fractures are the most common carpal fractures. They often need to be treated by surgery, where the use of a compression screw is the globally accepted gold standard. Surgeons may choose between different implant materials including titanium alloys, which remain in the body or are removed after healing. An alternative are biodegradable magnesium-based implants. Properties of magnesium alloys include high stability, osteoconductivity, potential reduction of infections and few artifacts in magnetic resonance imaging (MRI). The aim of this trial is to demonstrate non-inferiority of magnesium-based compression screws compared with titanium Herbert screws for scaphoid fractures.

Methods

The trial is designed as a multicenter, blinded observer, randomized controlled parallel two-group post market trial. Approximately 190 patients will be randomized (1:1) with stratification by center either to titanium or magnesium-based compression screws. Follow-up is 1 year per patient. Surgical procedures and aftercare will be performed according to the German treatment guideline for scaphoid fractures. The first primary endpoint is the patient-rated wrist evaluation (PRWE) score after 6 months. The second primary endpoint is a composite safety endpoint including bone union until 6 months, no adverse device effect (ADE) during surgery or wound healing and no serious ADE or reoperation within 1 year. The third primary endpoint is the difference in change MRI artifacts over time. Non-inferiority will be investigated for primary endpoints 1 (t-test confidence interval) and 2 (Wilson’s score interval) using both the full analysis set (FAS) and the per protocol population at the one-sided 2.5% test-level. Superiority of magnesium over titanium screws will be established using the FAS at the two-sided 5% test-level (Welch test) only if non-inferiority has been established for both primary endpoints. Secondary endpoints include quality of life.

Discussion

This study will inform care providers whether biodegradable magnesium-based implants are non-inferior to standard titanium Herbert screws for the treatment of scaphoid fractures in terms of wrist function and safety. Furthermore, superiority of magnesium-based implants may be demonstrated using MRI, which is used as surrogate endpoint for screw degradation.

Trial registration

DRKS, DRKS00013368. Registered Dec 04, 2017.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2723-9) contains supplementary material, which is available to authorized users.

Comparison of magnesium versus titanium screw fixation for biplane chevron medial malleolar osteotomy in the treatment of osteochondral lesions of the talus

PURPOSE

This retrospective study aimed to compare the clinical and radiological outcomes of patients who underwent biplane chevron medial malleolar osteotomy (MMO) for osteochondral lesions of the talus (OLT), fixed with either magnesium (Mg) or titanium (Ti) screws.

METHODS

A total of 22 patients (12 male and 10 female) with a mean age of 40.6 ± 12.5 years (range 18-56 years) who underwent MMO for OLT treatment were included in this retrospective study. Of the 22 patients, MMO was fixed with bioabsorbable Mg screws (Alloy: MgYREZr) in 11 patients, and in the remaining 11 patients (one bilateral) MMO was fixed with Ti screws. All patients were followed up for at least 1 year with a mean of 20.7 ± 8.9 months (range 12-49 months). The American Orthopedic Foot and Ankle Society (AOFAS) scale and the visual analog scale (VAS) were used to evaluate the clinical results. Union of the osteotomy, postoperative displacement and all other complications were followed and analyzed.

RESULTS

An improvement in the AOFAS scale and VAS points were recorded in both groups with no statistically significant difference between the groups (p 0.079 and 0.107, respectively). Complete union of the osteotomy was obtained in all patients. One patient in the Ti group required implant removal due to pain and irritation. There were no other significant complications in either group.

CONCLUSIONS

The results of this study showed that bioabsorbable Mg compression screws have similar therapeutic efficacy to Ti screws in respect of functional and radiological outcomes in MMO fixation. Bioabsorbable Mg screw is an alternative fixation material which can be safely used for MMO in ankle surgery.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Hallux valgus correction utilising a modified short scarf osteotomy with a magnesium biodegradable or titanium compression screws - a comparative study of clinical outcomes

BACKGROUND

Biodegradable implants reduce the likelihood of further surgery for hardware removal and reduce the risks of associated infection and allergy. The purpose of this study is to evaluate the clinical efficacy and determine the comparability of biodegradable magnesium alloy MgYREZr (MAGNEZIX® CS) compression screw fixation compared with standard titanium screw fixation in the surgical treatment of hallux valgus deformity.

METHODS

Eleven patients undergoing corrective surgery for hallux valgus utilising biodegradable magnesium screws and a control group of 25 patients undergoing corrective hallux valgus surgery with standard titanium screws were reviewed at a median of 19 months (range 12-30 months). PROM scores (Manchester-Oxford Foot Questionnaire (MOXFQ), Foot and Ankle Outcomes Instrument (FAOI) and the EQ-5D-3 L) were recorded preoperatively and at latest follow-up.

RESULTS

The results between the two groups were broadly similar, with the Magnesium and Titanium patients showing similar patterns in the various domains in the MOXFQ, the FAOI and the EQ-5D-3 L. Most patients reported a near full shoe comfort score, and EQ-5D-3 L scores were significantly improved in both patient groups (with most patients reporting a full score). Foot pain and foot function improved irrespective of the scoring systems and patients in both groups demonstrated significantly improved scores following the surgery (p < 0.05). Notably, there were no significant differences when comparing the post-operative scores between the groups for any individual scoring parameter. No impairment to quality of life was recorded. There were no intra or post-operative complications. There were no problems encountered through the use of the bioabsorbable screws.

CONCLUSION

Biodegradable magnesium-based compression screws appeared to be safe in this study and are an effective fixation device in the treatment of hallux valgus deformity with clinical outcomes similar to standard titanium screw fixation.

Single- vs 2-Screw Lag Fixation of the Medial Malleolus in Unstable Ankle Fractures

BACKGROUND

The purpose of this study was to determine the efficacy of medial malleolar fixation with 1 vs 2 screws.

METHODS

Between April 2013 and February 2017, 196 patients who presented at 2 hospitals within one academic institution with an unstable rotational ankle fracture with a medial fracture and were treated operatively by a trained orthopedic surgeon were identified. These patients' charts were reviewed and their injury, radiographic, surgical, and follow-up data recorded. Medial malleolus fragment size was assessed on the anteroposterior (AP) and lateral views of the initial injury radiograph. Functional outcome was assessed using Maryland Foot Score (MFS). Patients were grouped based upon the number of screws utilized to fox the medial malleolar fragment. Data were assessed using Fisher exact tests and independent t tests with SPSS, version 23.

RESULTS

Out of the 196 patients who met inclusion criteria, 47 patients (24%) were fixed with 1 medial malleolar screw and 149 patients (76%) were fixed with 2 screws. There were no differences among patients who received 1 vs 2 screws with regard to age, gender, body mass index, American Society of Anesthesiologists grade, or smoking status. The average malleolar fragment size was smaller in those treated with 1 screw on both the AP and lateral radiographic views than those with 2 screws (P = .009, P = .001, respectively). There was no difference between groups in ankle dorsiflexion or plantarflexion at 1 year postoperation (P = .451, P = .581). Patients who received 1 screw did not differ from those who received 2 screws with respect to Maryland Foot Scores (P = .924). There was no difference in rate of revision surgery or need for hardware removal between groups (P = .093). Furthermore, time to healing and postoperative complication rate did not differ between groups.

CONCLUSION

The use of a single screw for medial malleolar fixation provided stable fixation to allow ankle fracture healing, without an increase in complications. This information is especially important in situations when the fragment is too small to accommodate multiple fixation points.

LEVEL OF EVIDENCE

Level III, retrospective case-control study.

Fixation of Small Osteochondral Fragments in a Comminuted Distal Humerus Fracture with Magnesium Bioabsorbable Screws: A Case Report

The treatment of comminuted distal humeral fractures with free osteochondral fragments is challenging. Osteochondral fragments should be retained whenever possible and secured with implants buried beneath the articular surface to obtain a uniform articular surface. Headless compression screws and K wires are commonly used for this purpose. However, certain complications have been reported with these fixation implants in case of the non-union and osteolysis of the fragments such as migration and cartilage damage. Fixation of osteochondral fractures in distal humeral fractures using bioabsorbable implants has been rarely reported in the current literature. Herein, a patient who sustained a comminuted distal humeral fracture with multi-fragmentary osteochondral fragments is presented, and treatment with magnesium bioabsorbable compression screws is discussed.

Electrochemical Behavior of Biodegradable FeMnSi–MgCa Alloy

Nowadays, alongside metallic biomaterials, there is increasing interest in using degradable metals in an appreciable number of medical applications. There are new kinds of metallic biomaterials for medical applications and many new findings have been reported over the past few years. Iron-based materials are a solution for biodegradable applications based on their mechanical and chemical properties. In order to control the corrosion rate of the Fe10Mn6Si alloy, we proposed the use of two additional elements, Ca and Mg, as corrosion promoters. The new material was obtained in an air-controlled atmosphere furnace after five melting operations. The material was in vitro analyzed from a corrosion resistance point of view. The experiments were realized by immersion (7, 14, and 30 days) in simulated body fluid (SBF) solution at 37 °C and a constant pH, and by electrochemical tests (electrochemical impedance spectroscopy (EIS), linear polarization (LP), cyclic polarization (CP)). Material surfaces before and after corrosion tests were analyzed through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) techniques. A discussion on the degradation rate of the material was realized from a comparison of the results. The results presented good composition homogeneity after the re-melting stages, with low percentages of Ca and Mg in the material, but with an adequate spread in the alloy.