The toxicity of alloying elements in magnesium alloys used for biomedical purposes is an interesting and innovative subject, due to the great technological advances that would result from their application in medical devices (MDs) in traumatology. Recently promising results have been published regarding the rates of degradation and mechanical integrity that can support Mg alloys; this has led to an interest in understanding the toxicological features of these emerging biomaterials. The growing interest of different segments of the MD market has increased the determination of different research groups to clarify the behavior of alloying elements in vivo. This review covers the influence of the alloying elements on the body, the toxicity of the elements in Mg-Zn-Ca, as well as the mechanical properties, degradation, processes of obtaining the alloy, medical approaches and future perspectives on the use of the Mg in the manufacture of MDs for various medical applications.

This work focuses on the biomechanical simulation of surgery for total replacement of the first metatarsophalangeal joint (MTPJ) allowed us to identify and analyze several key aspects for finite element simulation of hallux rigidus pathology. Predicting the optimal response of a finite element model (FEM) depends on proper characterization. At this part of the work, those conditions that have a direct or indirect influence on the model that can change its behavior should be considered. For this purpose, we presented in this work a finite element model which include 26 bones: 14 phalanges, 5 metatarsals, 3 cuneiform bones, 1 cuboid, 1 navicular, 1 talus and 1 calcaneus, all of them include articular cartilage. In addition, the model also considers: thin ligaments, long ligaments, muscles and a joint implant. Loads and boundary conditions included: a pretension in the flexor caused by position analysis, a distributed load in the talus in its normal and tangential component, a restriction of movement of some points in the phalanges and calcaneus and the contact conditions between flexor and extensor created from surfaces in the bone volumes. Moreover, the selection of support and constrains regions in the phalanges and calcaneus area must be carefully selected to reproduce the conditions of real support and interaction with adjacent tissues not simulated. These conditions have influence in the structural biomechanical response of each tissue and in contact regions, leading to unexpected behavior if they are wrong selected. In addition, results showed that care must be taken in the mechanical characterization of each tissue, selecting the mechanical properties, pretension, geometry and critical position according to in vitro results or MRIs. Biomechanical aspects reported in this work allow to take into account fundamental details to improve future simulations of this pathology as well as to improve the correlation with experimental results. These biomechanical aspects provide knowledge for finite element simulation of the arthroplasty for the first metatarsophalangeal joint, this allow us to generate a virtual model for arthroplasty of the hallux rigidus to predict, prevent and improve surgical techniques for implantation of prostheses in the first metatarsophalangeal joint.

Bone allografts, which are used as bone regeneration material, must satisfy two functions: a biologic function and a mechanical function. The biologic task is satisfied by enrichment of the osseous reconstructive material with mesenchymal cells, radio-sterilized and lyophilized, which helps to a more efficient formation of new bone. Regarding the mechanical function, the allografts must be as rigid and strong as intact bone for immediate load-bearing capability. Consequently, a good mechanical characterization is needed to guarantee the structural integrity of the allografts in the host tissue. Thus, in this work results are presented from compression testing of cancellous and cortical/cancellous allograft tissue chips, as well as results on flexure and pure shear testing of cortical allograft strips. The test specimens were fabricated according to standard procedures. For the cancellous graft chips, different elastic moduli were obtained a long the three perpendicular directions, 32.2, 98.2, and 162.4 MPa, showing orthotropic behavior. For the cortical/cancellous chips, compression loads were only applied along the longitudinal and transversal directions of the cortical phase; the corresponding elastic moduli displayed were 518.6 and 384.8 MPa. On the other hand, for the cortical graft strips, the flexure elastic modulus obtained was 38.9 GPa; reported flexure elastic modulus in the literature for fresh human bone are between 1.525 and 31.5 GPa. Finally the shear strength exhibited by the cortical graft was 43.6 MPa.

The finite element analysis is a useful tool to investigate the behavior of a body subjected to different loads. The objective of this work was the analysis of an aluminum diesel piston provided with a cooling gallery, Cu-Zn bushings, and a Ni-resist insert. This piston is used in 1.9 L turbodiesel engines. The investigation was undertaken in order to observe the mechanical behavior of the piston at the operating temperatures and pressures and thus to study the performance of the different parts of the piston. The analysis was performed using a finite element software, taking into account a coupled field analysis and involving a fluid passing through the cooling gallery, temperature and pressure at the piston head which resulted in heat flow and thermo-mechanical stresses in the piston. According to the obtained results, it is worth noting the important role of Cu-Zn bushings in the piston as they support the highest stress of about 359 MPa and protect the piston against failure, and these bushings are able to support more stress that the body of the piston (aluminum yield stress limit 290 MPa). Also it is observed that the cooling gallery acts as a thermal barrier by preventing the heat flow from the head piston (approximately 213 ° C) toward the piston body (approximately 80 ° C). Another important aspect is the structural thermal interaction analysis and it can be observed the influence of high temperatures in the piston, increasing stress up to 100%. Finally it was concluded that the piston is able to withstand the operating pressures and temperatures.

Background: The aim of the study is to characterize a biomedical magnesium alloy and highlighting the loss of mechanical integrity due to the sterilization method. Ideally, when using these alloys is to delay the onset of degradation so that the implant can support body loads and avoid toxicological effects due to the release of metal ions into the body. Methods: The experimentation was carried out according to the standards of ASTM-F-1264 and ISO-10993-5 for mechanical and biological tests respectively, this testing methodology is carried out in accordance with the monographs of the Pharmacopoeia for the approval of medical devices and obtaining a health registration. An intramedullary implant (IIM) manufactured in magnesium (Mg) WE43 can support loads of the body in the initial period of bone consolidation without compromising the integrity of the fractured area. A system with these characteristics would improve morbidity and health costs by avoiding secondary surgical interventions. As a property, the fatigue resistance of Mg in aggressive environments such as the body environment undergoes progressive degradation, however, the autoclave sterilization method drastically affects fatigue resistance, as demonstrated in tests carried out under in vitro conditions. Coupled with this phenomenon, the relatively poor biocompatibility of Mg WE43 alloys has limited applications where they can be used due to low acceptance rates from agencies such as the FDA. However, Mg alloy with elements such as yttrium and rare earth elements (REEs) have been shown to delay biodegradation depending on the method of sterilization and the physiological solution used.Results: With different sterilization techniques, it may be possible to keep toxicological effects to a minimum while still ensuring a balance between the integrity of fractured bone and implant degradation time. Therefore, the evaluation of fatigue resistance of WE43 specimens sterilized and tested in immersion conditions (enriched Hank's solution) and according to ASTM F-1264, along with the morphological, crystallinity, and biocompatibility characterization of the WE43 alloy allows for a comprehensive evaluation of the mechanical and biological properties of WE43. Conclusions: These results will support decision-making to generate a change in the current perspective of biomaterials utilized in medical devices (MDs), to be considered by manufacturers and health regulatory agencies. An implant manufactured in WE43 alloy can be used as an intramedullary implant, considering keeping elements such as yttrium-REEs below as specified in its designation and with the help of a coating that allows increasing the life of the implant in vivo.