In vitro and in vivo degradation behavior of Mg–2Sr–Ca and Mg–2Sr–Zn alloys

Self Cite

Displaced fractures of patella often require open reduction surgery and internal fixation to restore the extensor continuity and articular congruity. Fracture fixation with biodegradable magnesium (Mg) pins enhanced fracture healing. We hypothesized that fixation with Mg pins and their degradation over time would enhance healing of patellar fracture radiologically, mechanically, and histologically. Transverse patellar fracture surgery was performed on thirty-two 18-weeks old female New Zealand White Rabbits. The fracture was fixed with a pin made of stainless steel or pure Mg, and a figure-of-eight stainless steel band wire. Samples were harvested at week 8 or 12, and assessed with microCT, tensile testing, microindentation, and histology. Microarchitectural analysis showed that Mg group showed 12% higher in the ratio of bone volume to tissue volume at week 8, and 38.4% higher of bone volume at week 12. Tensile testing showed that the failure load and stiffness of Mg group were 66.9% and 104% higher than the control group at week 8, respectively. At week 12, Mg group was 60.8% higher in ultimate strength than the control group. Microindentation showed that, compared to the Control group, Mg group showed 49.9% higher Vickers hardness and 31% higher elastic modulus at week 8 and 12, respectively. At week 12, the new bone of Mg group remodelled to laminar bone, but those of the control group remained woven bone-like. Fixation of transverse patellar fracture with Mg pins and its degradation enhanced new bone formation and mechanical properties of the repaired patella compared to the Control group.

Section: Discussionmentioning

confidence: 99%

Biodegradable magnesium pins enhanced the healing of transverse patellar fracture in rabbits

Chow

Wang

Wan

et al. 2021

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“…For example, the addition of appropriate Zn content into Mg–Ca alloys enhanced the corrosion resistance due to the changes in the corrosion potential in the second phase [ 70 ]. Chen et al [ 71 ] reported that the addition of Ca or Zn in the Mg–2Sr alloys enhanced the in vitro and in vivo corrosion resistance of the binary alloys because of the refined microstructure. Silver has been commonly used to improve the mechanical properties of binary Mg-based alloys.…”

Section: Current Strategies To Address Challenges Of Mg or Its Alloysmentioning

confidence: 99%

Clinical translation and challenges of biodegradable magnesium-based interference screws in ACL reconstruction

Luo

Zhang

Wang³

et al. 2021

Self Cite

As one of the most promising fixators developed for anterior cruciate ligament (ACL) reconstruction, biodegradable magnesium (Mg)-based interference screws have gained increasing attention attributed to their appropriate modulus and favorable biological properties during degradation after surgical insertion. However, its fast degradation and insufficient mechanical strength have also been recognized as one of the major causes to limit their further application clinically. This review focused on the following four parts. Firstly, the advantages of Mg or its alloys over their counterparts as orthopaedic implants in the fixation of tendon grafts in ACL reconstruction were discussed. Subsequently, the underlying mechanisms behind the contributions of Mg ions to the tendon-bone healing were introduced. Thirdly, the technical challenges of Mg-based interference screws towards clinical trials were discussed, which was followed by the introduction of currently used modification methods for gaining improved corrosion resistance and mechanical properties. Finally, novel strategies including development of Mg/Titanium (Ti) hybrid fixators and Mg-based screws with innovative structure for achieving clinically customized therapies were proposed. Collectively, the advancements in the basic and translational research on the Mg-based interference screws may lay the foundation for exploring a new era in the treatment of the tendon-bone insertion (TBI) and related disorders.

“…One of the effective methods to enhance the corrosion resistance of Mg-based implants is alloying. Many elements are added to Mg substrate to develop various types of Mg alloys, such as Mg-Ca, Mg-Sr, Mg-Li and Mg-Zn-Ca [ [10] , [11] , [12] ]. However, the fast degradation in the initial period of implantation is inevitable, because the intrinsic low standard potential of Mg (−2.37 V vs NHE) [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

Osteogenesis, angiogenesis and immune response of Mg-Al layered double hydroxide coating on pure Mg

Cheng

Zhang

et al. 2021

Layered double hydroxides (LDHs) are widely studied to enhance corrosion resistance and biocompatibility of Mg alloys, which are promising bone implants. However, the influence of LDH coating on the osteointegration of Mg implants lacks of a systematic study. In this work, Mg-Al LDH coating was prepared on pure Mg via hydrothermal treatment. The as-prepared Mg-Al LDH coated Mg exhibited better in vitro and in vivo corrosion resistance than bare Mg and Mg(OH) 2 coated Mg. In vitro culture of mouse osteoblast cell line (MC3T3-E1) suggested that Mg-Al LDH coated Mg was more favorable for its osteogenic differentiation. In vitro culture of HUVECs revealed that cells cultured in the extract of Mg-Al LDH coated Mg showed superior angiogenic behaviors. More importantly, the immune response of Mg-Al LDH coated Mg was studied by in vitro culturing murine-derived macrophage cell line (RAW264.7). The results verified that Mg-Al LDH coated Mg could induce macrophage polarize to M2 phenotype (anti-inflammatory). Furthermore, the secreted factor in the macrophage-conditioned culture medium of Mg-Al LDH group was more suitable for the bone differentiation of rat bone marrow stem cells (rBMSCs) and the angiogenic behavior of human umbilical vein endothelial cells (HUVECs). Finally, the result of femoral implantation suggested that Mg-Al LDH coated Mg exhibited better osteointegration than bare Mg and Mg(OH) 2 coated Mg. With favorable in vitro and in vivo performances, Mg-Al LDH is promising as protective coating on Mg for orthopedic applications.