The Safety of Micro-Implants for the Brain

Technological advancements in electronics and micromachining now allow the development of discrete wireless brain implantable micro-devices. Applications of such devices include stimulation or sensing and could enable direct placement near regions of interest within the brain without the need for electrode leads or separate battery compartments that are at increased risk of breakage and infection. Clinical use of leadless brain implants is accompanied by novel risks, such as migration of the implant. Additionally, the encapsulation material of the implants plays an important role in mitigating unwanted tissue reactions. These risks have the potential to cause harm or reduce the service of life of the implant. In the present study, we have assessed post-implantation tissue reaction and migration of borosilicate glass-encapsulated micro-implants within the cortex of the brain. Twenty borosilicate glass-encapsulated devices (2 × 3.5 × 20 mm) were implanted into the parenchyma of 10 sheep for 6 months. Radiographs were taken directly post-surgery and at 3 and 6 months. Subsequently, sheep were euthanized, and GFAP and IBA-1 histological analysis was performed. The migration of the implants was tracked by reference to two stainless steel screws placed in the skull. We found no significant difference in fluoroscopy intensity of GFAP and a small difference in IBA-1 between implanted tissue and control. There was no glial scar formation found at the site of the implant’s track wall. Furthermore, we observed movement of up to 4.6 mm in a subset of implants in the first 3 months of implantation and no movement in any implant during the 3–6-month period of implantation. Subsequent histological analysis revealed no evidence of a migration track or tissue damage. We conclude that the implantation of this discrete micro-implant within the brain does not present additional risk due to migration.

A biomechanical comparison of steel screws versus PLLA and magnesium screws for the Latarjet procedure

Introduction The fixation of the coracoid process onto the glenoid is an important step of the Latarjet procedure, and implant-associated complications are a relevant and severe problem. This study compares the fixation strength and failure mode of two biodegradable materials with stainless-steel screws. Methods 24 Fresh-frozen cadaveric scapulae were divided into three groups of equal size and received a coracoid transfer. Cadavers were matched according to their bone mineral density (BMD). In group 1, small-fragment screws made of stainless steel were used. In the second group, magnesium screws were used, and in the third group, screws consisted of polylactic acid (PLLA). A continuously increasing sinusoidal cyclic compression force was applied until failure occurred, which was defined as graft displacement relative to its initial position of more than 5 mm. Results At 5-mm displacement, the axial force values showed a mean of 374 ± 92 N (range 219–479 N) in group 1 (steel). The force values in group 2 (magnesium) had a mean of 299 ± 57 N (range 190–357 N). In group 3 (PLLA), failure occurred at 231 ± 83 N (range 109–355 N). The difference between group 1 (steel) and group 2 (magnesium) was not statistically significant (P = 0.212), while the difference between group 1 (steel) and group 3 (PLLA) was significant (P = 0.005). Conclusion Stainless-Steel screws showed the highest stability. However, all three screw types showed axial force values of more than 200 N. Stainless steel screws and PLLA screws showed screw cut-out as the most common failure mode, while magnesium screws showed screw breakage in the majority of cases. Evidence Controlled laboratory study.

Viability of polyamide 12 intramedullary rods coated with hydroxyapatite in experimentally induced fractures in young roosters (white Plymouth rock)

The present study aimed the viability evaluation of solid intramedullary rods made with polyamide 12 and coated with hydroxyapatite in experimentally osteotomized humerus of young roosters (white Plymouth rock). Sixteen animals of 45 days old each were used. After general anesthesia, they underwent to complete transverse osteotomy of the right humerus diaphysis to implant the already described rods which filled the entire length of the medullary cavity and were fixed by two cortical stainless steel screws in each bone fragment. The surgical technique was well succeeded without any trans-operative intercurrence. Through clinical and radiographic examination, it was observed that soon after the anesthesia recovery, six rods (37,5%) broke next to the fracture focus and the same was noticed with the others (62,5%) on seventh day post-surgery. Based on the obtained results, it can be hypothesized that polyamide 12 rods resistance could have been affected by all the thermal stages necessary to its incorporation with hydroxyapatite. Furthermore, the roosters’ age may also have contributed to adverse outcomes. However, future researches will be necessary to confirm those hypotheses.

DMSO potentiates the suppressive effect of dronabinol, a cannabinoid, on sleep apnea and REM sleep

PurposeDimethyl sulfoxide (DMSO) is an amphipathic molecule with innate biological activity that also is used to dissolve both polar and nonpolar compounds in preclinical and clinical studies. Recent investigations of dronabinol, a cannabinoid, dissolved in DMSO demonstrated decreased sleep apnea frequency and time spent in REM sleep in rats. Here, we tested the effects of dronabinol dissolved in 25% DMSO (diluted in phosphate-buffered saline) to rule out potentiating effects of DMSO.MethodsSprague-Dawley rats were anesthetized and implanted with bilateral stainless steel screws into the skull for electroencephalogram recording and bilateral wire electrodes into the nuchal muscles for electromyogram recording. Each animal was recorded by polysomnography. The study was a fully nested, repeated measures crossover design, such that each rat was recorded following each of 8 intraperitoneal injections separated by three days: vehicle (25% DMSO/PBS); vehicle and CB1 antagonist (AM 251); vehicle and CB2 antagonist (AM 630); vehicle and CB1/CB2 antagonist; dronabinol (CB1/CB2 agonist); dronabinol and CB1 antagonist; dronabinol and CB2 antagonist; and dronabinol and CB1/CB2 antagonist. Sleep was manually scored into NREM and REM stages, and apneas were quantified.ResultsDronabinol dissolved in 25% DMSO did not suppress apnea or modify sleep efficiency compared to vehicle controls, in contrast to previously published results. However, dronabinol did suppress REM sleep, which is in line with previously published results.ConclusionsDronabinol in 25% DMSO partially potentiated dronabinol’s effects, suggesting a concomitant biological effect of DMSO on breathing during sleep.

Pengaruh Parameter Pemotongan Pada Proses Bubut Ulir (Threading) Terhadap Kepresisian Geometri Ulir Magnesium Paduan AZ31

Magnesium telah dikembangkan dalam bidang kedokteran yaitu sebagai material untuk implan dalam tubuh. Hasil penelitian sebelumnya menunjukan bahwa faktor utamanya adalah sifat magnesium sangat mirip dengan sifat tulang manusia. Sekrup AZ31 menunjukkan kekuatan tarik keluar yang serupa dengan sekrup stainless steel saat ditarik dari bahan tulang sintetis, dan tingkat degradasi jenis sekrup Mg-alloy di ruang tulang sumsum dan otot lebih cepat daripada di ruang tulang kortikal. Hal ini menunjukan bahwa pembuatan ulir pada magnesium AZ31 sangat mendukung untuk diaplikasikan pada bidang material biomedic. Kepresisian geometri ulir akan memberikan pengaruh terhadap kwalitas ulir, terutama pada saat ulir bekerja bila sudah digunakan sebagai penyambung tulang. Untuk mengatasi masalah tersebut, dapat dilakukan variasi pada parameter proses pemesinan magnesium, yaitu parameter pemotongan pada saat pembubutan ulir untuk mendapatkan hasil yang paling baik akurasinya. Hasil penelitian menunjukan nilai kesalahan tinggi ulir minimum yaitu 0,018188 mm didapatkan pada parameter kecepatan spindel 424 rpm dan kedalaman potong 0,433015. Nilai kesalahan jarak puncak ulir (pitch) minimum yaitu 0,0205 mm didapatkan pada parameter kecepatan spindel 212 rpm dan kedalaman potong 0,649523 mm. Nilai kesalahan sudut minimum yaitu 0,603 didapatkan pada parameter kecepatan spindel 212 rpm dan kedalaman potong 0,324761 mm. Magnesium has been developed in the field of medic as a material for implants. The results of previous studies show that the main factor is the characteristic of magnesium very similar to the characteristic of human bones. AZ31 screws show outward tensile strength similar to stainless steel screws when pulled from synthetic bone material, and the degradation rate of Mg-alloy screw types in the marrow and muscle bone space is faster than in cortical bone space. This shows that the screw making on magnesium AZ31 is very possible to be applied in the biomedical material field.The precision of the screw geometry will have an effect on the quality of the thread, especially when the screw works when it has been used as a bone joint. To overcome this problem, variations in the machining process parameters are carried out, the cutting parameters at the time of screw turning to get the best accuracy results. The results showed that the minimum screw depth error value is 0.018188 mm, obtained at the spindle speed parameter of 424 rpm and depth of cut 0.433015 mm. The minimum pitch error value is 0.0205 mm obtained on the parameters of the spindle speed of 212 rpm and depth of cut 0.649523 mm. The minimum angle error value is 0.603 ° obtained in the parameters of the spindle speed 212 rpm and the depth of cut 0.324761 mm.

Assessment of the load capacity of the anchorage system connecting the textured layer with the structural wall of large slab buildings in the lights of experimental research and FEM analysis

The goal of the article is to compare the results obtained from experimental tests of a new type of anchoring, connecting the texture layer with the structural layer in external wall elements, used in large-panel construction with the results from FEM analysis. Two types of samples were subjected to experimental tests: single-layer uniform concrete and three-layer concrete with embedded point anchors and analogous samples with glued anchors. The test elements used C 12/15 and C 30/37 concrete, 12 mm diameter anchors, made of steel corresponding to the grade of stainless steel screws class 5.8, Sika Anchorfix-1 resin and XPS polystyrene. As for the three-layer samples, when testing, two forces were applied: tearing and shearing due to the detachment of the textured layer. The ANSYS program was used for numerical modelling of the analyzed samples. 3D models were built in which solid elements were used. For steel anchors, the material characteristics were taken as a two-line elasticplastic reinforcement. The Drucker-Prager model was used in the concrete elements, the linear-elastic model was adopted for the resin, and the brittle model according to the linear-elastic fracture mechanics for the polystyrene.

Study on the Performance of Orthodontic Self-Drilling Correction Screw of Ti6Al4V and Stainless 316L

In this research, the performance of orthodontic self-drilling correction screw of Titanium alloy (Ti6Al4V) and stainless steel (Stainless 316L) was analyzed by using the finite element method. SolidWorks software was employed to design the 3D models. The dimensions and geometrical parameters of the mini-screw according to ASTM F543-07. The analysis was conducted by using Ansys software. The biomechanical test is carried out that includes the static bending test and the torsion test. Based on the analysis of the results of the tests, the initial stability of the stainless steel screw is slightly higher than the titanium alloy screw. However, in prolonged stress results, attention to interactions with biological organisms from the medical perspective, the titanium bone screw have more advantages. In terms of the maximum load, the titanium alloy screws are better than the stainless steel screws. In terms of stiffness, the stainless steel screws proved superior to the type of titanium alloy. The orthodontic self-drilling correction screw saving of about 30% of the torque and more stable compared to the nonself-drilling type.

Pull-Out Strength of Screws in Screw Chases: Part 2

This paper (Part 2 of 2) presents a study of the structural behavior of tension-loaded screws installed in screw chases in extruded aluminum profiles. This connection is commonly used to resist outward wind load on glass in curtainwalls and skylights. See Part 1 for details of the pull-out testing. Two types of chase, each with 1/4 in. (6.35 mm) diameter stainless steel screws were used: a flat chase with AB tapping screws (1/4-14; 14 threads per 25.4 mm) and F tapping screws (1/4-20; 20 threads per 25.4 mm), and a longitudinally ribbed chase with UNC-thread machine screws (1/4-20). The extrusions included six cross-section shapes (three with flat chases and three with ribbed chases) and three alloy-tempers.