Fatigue Failure from Inner Surfaces of Additive Manufactured Ti-6Al-4V Components.

Selective laser melting (SLM) is an additive manufacturing process for producing metallic components with complex geometries. A drawback of this process is the process-inherent poor surface finish, which is highly detrimental in materials submitted to fatigue loading situations. The goal of this work is to analyze the fatigue behavior of Ti-6Al-4V specimens with internal axial channels under the following different conditions: hole drilled, hole as manufactured, and hole threaded M4 × 0.7. All the cases studied showed a lower fatigue performance as compared with solid samples due to the surface roughness and geometry effect that produced a surface stress concentration leading to a reduction in fatigue strength. The fractography revealed that crack initiation occurred from the internal surface in all specimens with internal channel mostly from defects as unfused particles and lack of fusion zones, while for the solid specimens crack initiation was observed from the external surface due to insufficient fusion defect. The application of the Smith-Watson-Topper energy-based parameter was revealed to be a good tool for fatigue life prediction of the different series studied.

Optimization of an Arterialized Venous Fasciocutaneous Flap in the Abdomen of the Rat.

BACKGROUND: Although numerous experimental models of arterialized venous flaps (AVFs) have been proposed, no single model has gained widespread acceptance. The main aim of this work was to evaluate the survival area of AVFs produced with different vascular constructs in the abdomen of the rat. METHODS: Fifty-three male rats were divided into 4 groups. In group I (n = 12), a 5-cm-long and 3-cm-wide conventional epigastric flap was raised on the left side of the abdomen. This flap was pedicled on the superficial caudal epigastric vessels caudally and on the lateral thoracic vein cranially. In groups II, III, and IV, a similar flap was raised, but the superficial epigastric artery was ligated. In these groups, AVFs were created using the following arterial venous anastomosis at the caudal end of the flap: group II (n = 13) a 1-mm-long side-to-side anastomosis was performed between the femoral artery and vein laterally to the ending of the superficial caudal epigastric vein. In group III (n = 14), in addition to the procedure described for group II, the femoral vein was ligated medially. Finally, in group IV (n = 14), the superficial caudal epigastric vein was cut from the femoral vein with a 1-mm-long ellipse of adjacent tissue, and an end-to-side arterial venous anastomosis was established between it and the femoral artery. RESULTS: Seven days postoperatively, the percentage of flap survival was 98.89 ± 1.69, 68.84 ± 7.36, 63.84 ± 10.38, 76.86 ± 13.67 in groups I-IV, respectively. CONCLUSION: An optimized AVF can be produced using the vascular architecture described for group IV.

Brachial plexus morphology and vascular supply in the wistar rat.

INTRODUCTION: The rat is probably the animal species most widely used in experimental studies on nerve repair. The aim of this work was to contribute to a better understanding of the morphology and blood supply of the rat brachial plexus. MATERIAL AND METHODS: Thirty adult rats were studied regarding brachial plexus morphology and blood supply. Intravascular injection and dissection under an operating microscope, as well as light microscopy and scanning electron microscopy techniques were used to define the microanatomy of the rat brachial plexus and its vessels. RESULTS: The rat brachial plexus was slightly different from the human brachial plexus. The arterial and venous supply to the brachial plexus plexus was derived directly or indirectly from neighboring vessels. These vessels formed dense and interconnected plexuses in the epineurium, perineurium, and endoneurium. Several brachial plexus components were accompanied for a relatively long portion of their length by large and constant blood vessels that supplied their epineural plexus, making it possible to raise these nerves as flaps. DISCUSSION: The blood supply to the rat brachial plexus is not very different from that reported in humans, making the rat a useful animal model for the experimental study of peripheral nerve pathophysiology and treatment. CONCLUSION: Our results support the homology between the rat and the human brachial plexus in terms of morphology and blood supply. This work suggests that several components of the rat brachial plexus can be used as nerve flaps, including predominantly motor, sensory or mixed nerve fibers. This information may facilitate new experimental procedures in this animal model.

Introdução: O rato é provavelmente a espécie animal mais utilizada em estudos experimentais de reparação nervosa. Com este trabalho pretendeu-se aprofundar o conhecimento da morfologia e da vascularização do plexo braquial do rato.Material e Métodos: Trinta ratos adultos foram estudados relativamente à morfologia e vascularização do plexo braquial. As técnicas usadas foram a injecção intravascular e dissecção sob microscópio operatório, bem como técnicas de microscopia óptica e microscopia electrónica de varrimento.Resultados: Morfologicamente, o plexo braquial do rato é um pouco diferente do plexo braquial humano. O suprimento arterial e venoso do plexo braquial do rato deriva direta ou indiretamente dos vasos vizinhos. Estes vasos formam plexos vasculares densos e interconectados no epinervo, perinervo e endonervo. Vários componentes do plexo braquial do rato são acompanhados durante um trajecto relativamente longo por vasos sanguíneos relativamente calibrosos e constantes que fornecem o seu plexo epineural, tornando o seu levantamento como retalhos nervosos possível.Discussão: A vascularização do plexo braquial do rato não é muito diferente da reportada na espécie humana, tornando o rato um modelo animal útil para o estudo experimental da fisiopatologia e tratamento da patologia do nervo periférico.Conclusão: Os nossos resultados apoiam a homologia entre o rato e o Homem em termos de morfologia e vascularização do plexo braquial. Este trabalho sugere que vários componentes do plexo braquial do rato podem ser utilizados como retalhos nervosos, incluindo fibras predominantemente motoras, sensitivas ou fibras mistas.