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

Influence of implant base material on secondary bone healing: an in silico study

The implant material at the fracture site influences fracture healing not only from biological perspective but also from mechanical perspective. Biodegradable implants such as magnesium (Mg) based alloys have shown faster secondary bone healing properties as compared to bioinert implants such as titanium (Ti). The general reasoning behind this is the benefit of Mg from biocompatibility perspectives. We studied the effect of Ti and Mg as base materials for implants from mechanical perspectives, where we focused on the displacements at the fracture site of the tibia and their influence on the stimulus for bone healing. We found out that in comparison to Ti, Mg implants have minimal stress shielding problem, only which led to better mechanical stimulus at the fracture site.

Prospective evaluation of ultrasound features of magnesium-based bioabsorbable screw resorption in pediatric fractures

OBJECTIVE

Bioabsorbable magnesium-based alloy screws release gas upon resorption. The resulting findings in the adjacent soft tissues and joints may mimic infection. The aim of the study was to evaluate the ultrasound (US) findings in soft tissues and joints during screw resorption.

METHODS

Prospectively acquired US studies from pediatric patients treated with magnesium screws were evaluated for screw head visibility, posterior acoustic shadowing, twinkling artifact, foreign body granuloma, gas (soft tissue, intra-articular), alterations of the skin and subcutaneous fat, perifascial fluid, localized fluid collections, hypervascularization, and joint effusion.

RESULTS

Sixty-six US studies of 28 pediatric patients (nfemale = 9, nmale = 19) were included. The mean age of the patients at the time of surgery was 10.84 years; the mean time between surgery and ultrasound was 128.3 days (range = 6-468 days). The screw head and posterior acoustic shadowing were visible in 100% of the studies, twinkling artifact in 6.1%, foreign body granuloma in 92.4%, gas locules in soft tissue in 100% and intra-articular in 18.2%, hyperechogenicity of the subcutaneous fat in 90.9%, cobblestoning of the subcutaneous fat in 24.2%, loss of normal differentiation between the epidermis/dermis and the subcutaneous fat in 57.6%, localized fluid collection in 9.9%, perifascial fluid in 12.1%, hypervascularization in 27.3%, and joint effusion in 18.2%.

CONCLUSION

US findings in pediatric patients treated with magnesium screws strongly resemble infection, but are normal findings in the setting of screw resorption.

CLINICAL RELEVANCE STATEMENT

Bioabsorbable magnesium-based alloy screws release gas during resorption. The resulting US findings in the adjacent soft tissues and joints in pediatric patients may mimic infection, but are normal findings.

KEY POINTS

• Bioabsorbable magnesium-based alloy screws release gas upon resorption. • The resulting ultrasound findings in children's soft tissues and joints closely resemble those of soft tissue infection or osteosynthesis-associated infection. • Be familiar with these ultrasound findings in order to avoid inadvertently misdiagnosing a soft tissue infection or osteosynthesis-associated infection.

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.

Detailing the influence of PEO-coated biodegradable Mg-based implants on the lacuno-canalicular network in sheep bone: A pilot study

An increasing prevalence of bone-related injuries and aging geriatric populations continue to drive the orthopaedic implant market. A hierarchical analysis of bone remodelling after material implantation is necessary to better understand the relationship between implant and bone. Osteocytes, which are housed and communicate through the lacuno-canalicular network (LCN), are integral to bone health and remodelling processes. Therefore, it is essential to examine the framework of the LCN in response to implant materials or surface treatments. Biodegradable materials offer an alternative solution to permanent implants, which may require revision or removal surgeries. Magnesium alloys have resurfaced as promising materials due to their bone-like properties and safe degradation in vivo. To further tailor their degradation capabilities, surface treatments such as plasma electrolytic oxidation (PEO) have demonstrated to slow degradation. For the first time, the influence of a biodegradable material on the LCN is investigated by means of non-destructive 3D imaging. In this pilot study, we hypothesize noticeable variations in the LCN caused by altered chemical stimuli introduced by the PEO-coating. Utilising synchrotron-based transmission X-ray microscopy, we have characterised morphological LCN differences around uncoated and PEO-coated WE43 screws implanted into sheep bone. Bone specimens were explanted after 4, 8, and 12 weeks and regions near the implant surface were prepared for imaging. Findings from this investigation indicate that the slower degradation of PEO-coated WE43 induces healthier lacunar shapes within the LCN. However, the stimuli perceived by the uncoated material with higher degradation rates induces a greater connected LCN better prepared for bone disturbance.

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.

Prospective Evaluation of Magnetic Resonance Imaging Features of Magnesium-Based Alloy Screw Resorption in Pediatric Fractures

BACKGROUND

The resorption of magnesium-based alloy bioabsorbable screws results in the release of hydrogen gas, which can mimic infection and enter the growth plate. The screw itself and the released gas may also affect image quality.

OBJECTIVE

The evaluation of magnetic resonance imaging (MRI) findings during the most active phase of screw resorption is the objective, with particular focus on the growth plate and to assess for the presence of metal-induced artifacts.

MATERIAL AND METHODS

In total, 30 prospectively acquired MRIs from 17 pediatric patients with fractures treated with magnesium screws were assessed for the presence and distribution of intraosseous, extraosseous, and intra-articular gas; gas within the growth plate; osteolysis along the screw; joint effusion; bone marrow edema; periosteal reaction; soft tissue edema; and metal-induced artifacts.

RESULTS

Gas locules were found in the bone and soft tissues in 100% of the examinations, intra-articular in 40%, and in 37% of unfused growth plates. Osteolysis and the periosteal reaction were present in 87%, bone marrow edema in 100%, soft tissue edema in 100%, and joint effusion in 50% of examinations. Pile-up artifacts were present in 100%, and geometric distortion in 0% of examinations. Fat suppression was not significantly impaired in any examination.

CONCLUSIONS

Gas and edema in the bone and soft tissues are normal findings during the resorption of magnesium screws and should not be misinterpreted as infection. Gas can also be detected within growth plates. MRI examinations can be performed without metal artifact reduction sequences. Standard fat suppression techniques are not significantly affected.

The combined effect of zinc and calcium on the biodegradation of ultrahigh-purity magnesium implants

Magnesium (Mg)-based implants are promising candidates for orthopedic interventions, because of their biocompatibility, good mechanical features, and ability to degrade completely in the body, eliminating the need for an additional removal surgery. In the present study, we synthesized and investigated two Mg-based materials, ultrahigh-purity ZX00 (Mg-Zn-Ca; <0.5 wt% Zn and <0.5 wt% Ca, in wt%; Fe-content <1 ppm) and ultrahigh-purity Mg (XHP-Mg, >99.999 wt% Mg; Fe-content <1 ppm), in vitro and in vivo in juvenile healthy rats to clarify the effect of the alloying elements Zn and Ca on mechanical properties, microstructure, cytocompatibility and degradation rate. Potential differences in bone formation and bone in-growth were also assessed and compared with state-of-the-art non-degradable titanium (Ti)-implanted, sham-operated, and control (non-intervention) groups, using micro-computed tomography, histology and scanning electron microscopy. At 6 and 24 weeks after implantation, serum alkaline phosphatase (ALP), calcium (Ca), and Mg level were measured and bone marrow stromal cells (BMSCs) were isolated for real-time PCR analysis. Results show that ZX00 implants have smaller grain size and superior mechanical properties than XHP-Mg, and that both reveal good biocompatibility in cytocompatibilty tests. ZX00 homogenously degraded with an increased gas accumulation 12 and 24 weeks after implantation, whereas XHP-Mg exhibited higher gas accumulation already at 2 weeks. Serum ALP, Ca, and Mg levels were comparable among all groups and both Mg-based implants led to similar relative expression levels of Alp, Runx2, and Bmp-2 genes at weeks 6 and 24. Histologically, Mg-based implants are superior for new bone tissue formation and bone in-growth compared to Ti implants. Furthermore, by tracking the sequence of multicolor fluorochrome labels, we observed higher mineral apposition rate at week 2 in both Mg-based implants compared to the control groups. Our findings suggest that (i) ZX00 and XHP-Mg support bone formation and remodeling, (ii) both Mg-based implants are superior to Ti implants in terms of new bone tissue formation and osseointegration, and (iii) ZX00 is more favorable due to its lower degradation rate and moderate gas accumulation.

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.

Medial oblique malleolar osteotomy for approach of medial osteochondral lesion of the talus

PURPOSE

The medial malleolar osteotomy is commonly performed to gain access to the medial talar dome for treatment of osteochondral lesions of the talus. The primary aim of this study was to assess osseous healing based on postoperative radiographs to determine consolidation, non-union and malreduction rates.

METHODS

Sixty-seven cases were reviewed where an oblique uniplanar medial malleolar osteotomy was performed to gain access to the medial talar dome for addressing an osteochondral lesion. Two, respectively three fully threaded 3.5 mm corticalis screws were used to fixate the osteotomy. Postoperative radiographs were reviewed to assess consolidation, non-union, malreduction and dislocation of the osteotomy.

RESULTS

Out of 67 patients, 66 patients had a consolidation of the osteotomy. 23.9% of the cases showed malreduction of the osteotomy. One patient suffered a non-union, which required a revision surgery. No significant difference was shown between two and three screws used for fixation in terms of malreduction and consolidation of the osteotomy. Eighty-four percent of the patients underwent hardware removal due to pain or medial impingement.

CONCLUSION

The oblique medial malleolar osteotomy is a safe and relatively simple procedure with a high consolidation rate and low revision providing excellent exposure of the talus. The moderately high malreduction rate and required hardware removal surgery by most of the patients are relevant factors which should be considered before performing this surgery.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Biodegradable magnesium fixation screw for barrier membranes used in guided bone regeneration

An ideal fixation system for guided bone (GBR) regeneration in oral surgery must fulfil several criteria that includes the provision of adequate mechanical fixation, complete resorption when no longer needed, complete replacement by bone, as well as be biocompatible and have a good clinical manageability. For the first time, a biodegradable magnesium fixation screw made of the magnesium alloy WZM211 with a MgF₂ coating has been designed and tested to fulfill these criteria. Adequate mechanical fixation was shown for the magnesium fixation screw in several benchtop tests that directly compared the magnesium fixation screw with an equivalent polymeric resorbable device. Results demonstrated slightly superior mechanical properties of the magnesium device in comparison to the polymeric device even after 4 weeks of degradation. Biocompatibility of the magnesium fixation screw was demonstrated in several in vitro and in vivo tests. Degradation of the magnesium screw was investigated in in vitro and in vivo tests, where it was found that the screw is resorbed slowly and completely after 52 weeks, providing adequate fixation in the early critical healing phase. Overall, the magnesium fixation screw demonstrates all of the key properties required for an ideal fixation screw of membranes used in guided bone regeneration (GBR) surgeries.

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The first comprehensive report on experimental data for a biodegradable metallic fixation pin for use in oral surgery is presented.

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Results demonstrated superior mechanical properties of the Mg fixation pin in comparison to the polymeric pin even after 4 weeks of degradation.

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The MgF₂ coated Mg pin made of alloy WZM211 has a slow corrosion rate with a service time of 4 weeks and is fully resorped at 52 weeks after implantation.

Biodegradable open-porous scaffolds made of sintered magnesium W4 and WZ21 short fibres show biocompatibility in vitro and in long-term in vivo evaluation

Open-porous scaffolds made of W4 and WZ21 fibres were evaluated to analyse their potential as an implant material. WZ21 scaffolds without any surface modification or coating, showed promising mechanical properties which were comparable to the W4 scaffolds tested in previous studies. Eudiometric testing results were dependent on the experimental setup, with corrosion rates differing by a factor of 3. Cytotoxicity testing of WZ21 showed sufficient cytocompatibility. The corrosion behavior of the WZ21 scaffolds in different cell culture media are indicating a selective dealloying of elements from the magnesium scaffold by different solutions. Long term in-vivo studies were using 24 W4 scaffolds and 12 WZ21 scaffolds, both implanted in rabbit femoral condyles. The condyles and important inner organs were explanted after 6, 12 and 24 weeks and analyzed. The in-vivo corrosion rate of the WZ21 scaffolds calculated by microCT-based volume loss was up to 49 times slower than the in-vitro corrosion rate based on weight loss. Intramembranous bone formation within the scaffolds of both alloys was revealed, however a low corrosion rate and formation of gas cavities at initial time points were also detected. No systemic or local toxicity could be observed. Investigations by μ-XRF did not reveal accumulation of yttrium in the neighboring tissue. In summary, the magnesium scaffold´s performance is biocompatible, but would benefit from a surface modification, such as a coating to obtain lower the initial corrosion rates, and hereby establish a promising open-porous implant material for load-bearing applications. STATEMENT OF SIGNIFICANCE: Magnesium is an ideal temporary implant material for non-load bearing applications like bigger bone defects, since it degrades in the body over time. Here we developed and tested in vitro and in a rabbit model in vivo degradable open porous scaffolds made of sintered magnesium W4 and WZ21 short fibres. These scaffolds allow the ingrowth of cells and blood vessels to promote bone healing and regeneration. Both fibre types showed in vitro sufficient cytocompatibility and proliferation rates and in vivo, no systemic toxicity could be detected. At the implantation site, intramembranous bone formation accompanied by ingrowth of supplying blood vessels within the scaffolds of both alloys could be detected.

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.

Alterations in magnetic resonance imaging characteristics of bioabsorbable magnesium screws over time in humans: a retrospective single center study

Objectives

This study aimed to examine the alterations in magnetic resonance imaging (MRI) characteristics of bioabsorbable magnesium (Mg) screws over time in a single center study in humans.

Methods

Seventeen patients who underwent medial malleolar (MM) fracture or osteotomy fixation using bioabsorbable Mg screws and had at least one postoperative MRI were included in this retrospective study. Six of them had more than one MRI in the postoperative period and were subject of the artifact reduction measurements. 1.5T or 3T MRI scans were acquired in different periods in each patient. The size and extent of the artifact were assessed independently by two experienced radiologists both quantitatively (distance measurement) and qualitatively (Likert scale).

Results

In the quantitative measurements of the six follow-up patients the screw’s signal loss artifact extent significantly decreased over the time, regardless of the MRI field strength (p<0.001). The mean artifact reduction was 0.06 mm (95% confidence interval [CI]: 0.05–0.07) for proton density weighted [PDw] and 0.04 mm (95% CI: 0.03–0.05) for T1 weighted (T1w) sequences per week. The qualitative assessments similarly showed significant artifact reduction in all MRI sequences. Different imaging findings, like bone marrow edema (BME), liquid collections, and gas formation were reported. The overall inter-reader agreement was high (κ=0.88, p<0.001).

Conclusions

The time-dependent artifact reduction of Mg screws in postoperative controls might indicate the expected self-degradation of the Mg implants. In addition, different MRI findings were reported, which are characteristic of Mg implants. Further MRI studies are required to get a better understanding of Mg imaging properties.

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.

Safety and performance of biodegradable magnesium-based implants in children and adolescents

AIMS

Biodegradable magnesium-based alloy implants represent a promising option in orthopedic surgery, as the clinical outcomes have been reported to be comparable to those of titanium implants and no surgical interventions are required for removal. To date, little is known about the results of the use of these implants in children and adolescents. Therefore, the aim of the present study was to analyze the safety and performance of these implants in children and adolescents.

PATIENTS AND METHODS

Eighty-nine patients treated with magnesium-based implants for fracture stabilization, osteotomy and osteochondral refixation were analyzed; 38 were treated by osteosynthesis; 18, osteotomy; and 33, osteochondral refixation. The mean follow-up duration was 8.2 months (range, 1.5-30 months). Clinical and radiographical follow-up examinations were performed at 4-8 weeks and 3-6 months, respectively, to evaluate implant performance and osseous consolidation.

RESULTS

Clinical outcomes were rated as good to very good in all patients. Radiolucent zones were apparent after surgery in all patients but were noted to decrease in size during the follow-up period. Revision surgery was necessary in 1 of 89 patients who had a highly unstable osteochondritis dissecans lesion of the knee. None of the magnesium-based implants required surgical removal.

CONCLUSION

Magnesium-based implants in children and adolescents results in good clinical outcomes when used for fracture stabilization, osteotomy and osteochondral defect refixation. Future studies are needed to further analyze the significance of the transient appearance and temporal development of radiolucent zones in the growing skeleton as well as the long-term performance of these implants.

Midterm Results Following Minimally Invasive Distal Chevron Osteotomy: Comparison With the Minimally Invasive Reverdin-Isham Osteotomy by Means of Meta-analysis

BACKGROUND/AIM

To date, multiple different surgical techniques have been established for hallux valgus surgery, with each technique having its unique advantages and limitations. The open distal chevron osteotomy is widely accepted, but increasing patient demands have led several minimally invasive (MIS) techniques to be described in recent years. The aim of this study was to compare outcomes after minimally invasive (MIS) distal chevron osteotomy and the minimally invasive Reverdin-Isham method.

PATIENTS AND METHODS

We assessed clinical and radiographic outcomes after MIS chevron osteotomy in 57 feet of 49 consecutive patients with a mean follow-up of 58.9 (range=39.0-85.4) months. Outcomes after MIS Reverdin-Isham osteotomy were analyzed by means of a systematic literature review with a minimum follow-up of 6 months.

RESULTS

Radiographic outcomes were significantly better in the MIS chevron cohort for intermetatarsal angle (p<0.001), hallux valgus angle and distal metacarpal articular angle (p<0.05). Concerning clinical outcomes, both methods provided comparable improvement.

CONCLUSION

MIS distal chevron osteotomy in mild to moderate hallux valgus deformity correction results in superior radiographic outcomes compared to the MIS Reverdin-Isham osteotomy. Sufficient correction of IMA cannot be achieved with the MIS Reverdin-Isham osteotomy.

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.

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.

Biocompatibility and degradation of the open-pored magnesium scaffolds LAE442 and La2

Porous magnesium implants are of particular interest for application as resorbable bone substitutes, due to their mechanical strength and a Young's modulus similar to bone. The objective of the present study was to compare the biocompatibility, bone and tissue ingrowth, and the degradation behaviour of scaffolds made from the magnesium alloys LAE442 (n= 40) and Mg-La2 (n= 40)in vivo. For this purpose, cylindrical magnesium scaffolds (diameter 4 mm, length 5 mm) with defined, interconnecting pores were produced by investment casting and coated with MgF₂. The scaffolds were inserted into the cancellous part of the greater trochanter ossis femoris of rabbits. After implantation periods of 6, 12, 24 and 36 weeks, the bone-scaffold compounds were evaluated usingex vivo µCT80 images, histological examinations and energy dispersive x-ray spectroscopy analysis. The La2 scaffolds showed inhomogeneous and rapid degradation, with inferior osseointegration as compared to LAE442. For the early observation times, no bone and tissue could be observed in the pores of La2. Furthermore, the excessive amount of foreign body cells and fibrous capsule formation indicates insufficient biocompatibility of the La2 scaffolds. In contrast, the LAE442 scaffolds showed slow degradation and better osseointegration. Good vascularization, a moderate cellular response, bone and osteoid-like bone matrix at all implantation periods were observed in the pores of LAE442. In summary, porous LAE442 showed promise as a degradable scaffold for bone defect repair, based on its degradation behaviour and biocompatibility. However, further studies are needed to show it would have the necessary mechanical properties required over time for weight-bearing bone defects.

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.

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.