Insertion torque and pullout strength of vertebral screws with cylindrical and conic core

OBJETIVO: Avaliar o torque de inserção e a força de arrancamento de três diferentes parafusos utilizados para a fixação anterior da coluna vertebral, considerando a influência do diâmetro do orifício-piloto (DOP), a densidade dos corpos de prova (CDP) e o desenho da rosca dos parafusos. MÉTODOS: Foram utilizados CDP de poliuretana com duas densidades: 0,16 e 0,32g/cm³, e três tipos de parafusos (USS I, USS II posterior e USS II anterior). Na primeira etapa o orifício-piloto foi feito com sonda de 3,8mm para todos os parafusos; na segunda etapa, com sonda menor do que o diâmetro interno dos parafusos (3,5mm para os parafusos USS I; 3,4mm para os parafusos USS II posterior e 3,0mm para os parafusos USS II anterior). Foram formados 12 grupos experimentais com dez corpos de prova em cada grupo, de acordo com a densidade da poliuretana, DOP e tipo de parafuso utilizado. O torque foi mensurado durante a inserção dos parafusos e a força de arrancamento por meio de ensaio mecânico em máquina universal de teste. RESULTADOS: O torque máximo de inserção apresentou valores decrescentes nos corpos de prova de 0,16g/cm³ e 0,32g/cm³ e em todos os diâmetros do orifício-piloto. A força máxima de arrancamento, nos corpos de prova de 0,16g/cm³ e diâmetro da perfuração de 3,8mm, foi maior nos parafusos USS II posterior que nos parafusos USS I. Com o diâmetro da perfuração menor do que o diâmetro interno do parafuso, os parafusos USS II posterior e anterior apresentaram valores maiores que o parafuso USS I. Nos corpos de prova com 0,32g/cm³ de densidade e diâmetro de perfuração de 3,8mm, a força de arrancamento do parafuso USS II posterior e a do USS I foram maiores que a do parafuso USS II anterior. Com o diâmetro da perfuração menor que o diâmetro interno, os valores foram decrescentes entre o USS II posterior, USS II anterior e USS I. CONCLUSÕES: O torque de inserção e a força de arrancamento dos parafusos utilizados para fixação anterior da coluna vertebral são influenciados pela densidade do corpo de prova, desenho da rosca do parafuso e diâmetro do orifício-piloto.OBJECTIVE: To evaluate insertion torque and pullout strength of three different screws used in the anterior fixation of the spine, considering the influence of the diameter of the pilot hole (DOP), the test specimen density (CDP), and the screw thread design. METHODS: The authors used polyurethane test specimens with two densities: 0.16 and 0.32 g/cm³, and three types of screws (USS I, USS II posterior, and USS II anterior). In the first stage, the pilot hole was made with a 3.8 mm probe for all screws; in the second stage, with a probe smaller than the inner diameter of the screws (3.5 mm for screws USS I; 3.4 mm for USS II posterior screws, and 3.0 mm for USS II anterior screws). 12 experimental groups were formed with ten specimen tests in each group, according to the polyurethane density, DOP, and the type of screw used. Torque was measured during insertion of the screws and the pullout strength by a mechanical assay in a universal test machine. RESULTS: The maximum insertion torque presented a decreasing value in test specimens of 0.16 g/cm³ and 0.32 g/cm³ and in all pilot hole diameters. Maximum pullout strength in test specimens of 0.16 g/cm³ and 3.8 mm of perforation diameter was greater in USS II posterior screws than in USS I screws. With the perforation diameter smaller than the inner screw diameter, USS II posterior and anterior screws presented higher values than the USS I screw. In test specimens with 0.32 g/cm³ of density and perforation diameter of 3.8 mm, the pullout strength of USS II posterior and USS I screws was greater than that of USS II anterior screws. With the smaller perforation diameter than the inner diameter, the values were decreasing between the USS II posterior screw, then the USS II anterior screw, and then the USS I screw. CONCLUSION: Insertion torque and pullout strength of the screws used in the anterior fixation of the vertebral spine are influenced by the test specimen density, by the screw thread design, and by the diameter of the pilot hole.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Biomechanical and histological analysis of the gastrocnemius in rats subjected to muscle injury and treatment with low-level laser therapy

OBJETIVO: Avaliar, mecânica e histologicamente, a aplicação do laser terapêutico de baixa potência, no processo reparativo de lesões provocadas por impacto em músculos gastrocnêmios de ratas. MÉTODOS: 45 ratas Wistar foram divididas em três grupos (n=15/grupo): C (controle, sem lesão), LM (lesão muscular) e LM-L (lesão muscular e laserterapia). A lesão muscular experimental foi produzida pela queda de uma carga de 250 g, de uma altura de 30cm, diretamente sobre o músculo. Os animais do grupo LM-L foram submetidos à aplicação de laser 960nm, 2J/cm², durante três dias, duas aplicações por dia, no local da lesão. Foi realizado ensaio mecânico na máquina universal de ensaio Emic®. RESULTADOS: As médias dos valores de força máxima foram: (35,70 ± 2,69) N no grupo C, (31,77 ± 2,59) N no grupo LM e (34,36 ± 3,63) N no grupo LM-L, com diferença estatística significativa nos grupos C e LM (p < 0,05). As médias dos valores de rigidez relativa foram (3,75 ± 0,98) N/mm no grupo C, (3,84 ± 0,32) N/mm no grupo LM e (4,43 ± 0,68) N/mm no grupo LM-L, sem diferença estatística (p &gt; 0,05). A análise histológica evidenciou presença de vasos sanguíneos no grupo LM-L e hematomas em processo de reparação. CONCLUSÃO: A laserterapia influencia de forma positiva no processo de regeneração da lesão muscular.OBJETIVE: To evaluate, by means of biomechanical and histological analysis, the effect of low-level laser therapy on the gastrocnemius of rats subjected to muscle lesion by impact. METHODS: 45 female Wistar rats, weighing 250g, were divided into 3 groups (n=15/group): C (control), ML (animals submitted to muscle lesion) and ML-L (animals submitted to muscle lesion and laser therapy). The animals from groups ML and ML-L were subjected to an experimental muscle lesion by means of an impact of a 250g load, released from a height of 30 cm, directly on the gastrocnemius. The animals from group ML-L were submitted to a treatment with a 960 Nm laser, 2 J/cm², for 3 days, twice a day. RESULTS: The mechanical tests were performed on the Universal Testing Machine. The average values of maximum force were: 35.70 (± 2.69) N in group C, 31.77 (± 2.59) N in group ML and 34.36 (± 3.63) N in group ML-L, with a statistically significant difference between groups C and ML (p < 0.05). The average values of stiffness were: 3.75 (± 0.98) N/mm in group C, 3.84 (± 0.32) N/mm in group ML and 4.43 (± 0.68) N/mm in group ML-L, with no statistically significant differences (p&gt;0.05). Histological analysis showed a presence of blood vessels in group ML-L and a hematoma in the healing stage. CONCLUSION: Treatment with low-level laser had a positive effect in the healing process of muscle injury

Association of Urinary and Blood Concentrations of Heavy Metals with Measures of Bone Mineral Density Loss: a Data Mining Approach with the Results from the National Health and Nutrition Examination Survey

Osteoporosis and its consequence of fragility fracture represent a major public health problem. Human exposure to heavy metals has received considerable attention over the last decades. However, little is known about the influence of co-exposure to multiple heavy metals on bone density. The present study aimed to examine the association between exposure to metals and bone mineral density (BMD) loss. Blood and urine concentrations of 20 chemical elements were selected from 3 cycles (2005–2010) NHANES (National Health and Nutrition Examination Survey), in which we included white women over 50 years of age and previously selected for BMD testing (N = 1892). The bone loss group was defined as participants having T-score < − 1.0, and the normal group was defined as participants having T-score ≥ − 1.0. We developed classification models based on support vector machines capable of determining which factors could best predict BMD loss. The model which included the five-best features-selected from the random forest were age, body mass index, urinary concentration of arsenic (As), cadmium (Cd), and tungsten (W), which have achieved high scores for accuracy (92.18%), sensitivity (90.50%), and specificity (93.35%). These data demonstrate the importance of these factors and metals to the classification since they alone were capable of generating a classification model with a high prediction of accuracy without requiring the other variables. In summary, our findings provide insight into the important, yet overlooked impact that arsenic, cadmium, and tungsten have on overall bone health

Photoelastic analisys in the lower region of vertebral body L4

OBJETIVO: Analisar as tensões geradas no corpo vertebral L4 quando submetida à força de compressão, utilizando a técnica da fotoelasticidade de transmissão. MÉTODOS: Doze modelos fotoelásticos foram utilizados e divididos em três grupos, sendo cada grupo formado por quatro modelos, de acordo com a localização do corte sagital nas vértebras L4-L5 (cortes A, B e C). A simulação foi realizada utilizando uma força compressão de 15 N e as ordens de franjas foram avaliadas no corpo vertebral L4 utilizando o método de compensação de Tardy. RESULTADOS: A análise fotoelástica mostrou que em geral, as tensões se distribuíram de forma homogênea nos corpos vertebrais. As tensões no corte C foram maiores que no B, que por sua vez foram maiores que no corte A. CONCLUSÃO: A região posterior do corpo vertebral L4, principalmente no corte C, apresentou maiores concentrações de tensões, sendo assim, é a área mais susceptível à fratura vertebral e à espondilolistese. Análises econômicas e de decisão. Desenvolvimento de modelo econômico ou de decisão, Nível de evidência I

Efeitos da aplicação do laser de baixa potência na regeneração do nervo isquiático de ratos

Os nervos periféricos sofrem constantes lesões de origem traumática, o que resulta em perdas funcionais. A terapia com laser de baixa potência vem sendo utilizada para minimizar os efeitos maléficos da inflamação e acelerar o processo de cicatrização dos tecidos lesados. Este estudo teve como objetivo verificar o efeito da irradiação do laser 830 nm no comportamento do nervo isquiático de ratos submetido a esmagamento. Foram utilizados 20 ratos, todos tendo tido o nervo isquiático esmagado, divididos em 4 grupos (n=5): P7 e P14, tratamento placebo por 7 e 14 dias; L7 e L14, tratamento por laser (dosagem de 4 J/cm²) por 7 e 14 dias. Os animais dos grupos P7 e P14 foram submetidos aos mesmos procedimentos, mas com o laser desligado. Os parâmetros analisados foram presença de infiltrado inflamatório e fibroblastos, destruição da bainha de mielina e degeneração axonal. Na análise estatística foi observada diferença estatística com relação a três parâmetros: os animais do grupo L14 apresentaram maior quantidade de fibroblastos (p=0,0001), menor degeneração da bainha de mielina (p=0,007) e menor quantidade de infiltrado inflamatório (p=0,001). A aplicação do laser de baixa potência contribuiu para a redução do processo inflamatório decorrente da lesão do nervo isquiático de ratos.Peripheral nerves are commonly subject to traumatic injuries, leading to functional loss. Low-power laser therapy has been used in order to minimize harmful effects of inflammation and to accelerate healing of injured tissues. The purpose of this study was to assess the effect of 830 nm-laser irradiation on rat sciatic nerves submitted to crush. Twenty male Wistar rats had their sciatic nerve crushed and were divided into 4 groups (n=5): Sham7 and Sham14, placebo-treated for 7 and 14 days; L7 and L14, laser-treated (at 4 J/cm²) for 7 and 14 days. Sham group animals were submitted to the same procedures, but with the laser turned off. Assessed parameters were inflammatory infiltrates, fibroblasts, myelin sheath destruction, and axonal degeneration. The statistical analysis showed significant differences in three parameters: L14 animals showed more fibroblasts (p=0.0001), lesser myelin sheath degeneration (p=0.007), and lesser inflammatory infiltrates (p=0.001). Low-power laser therapy hence contributed to reduce the inflammatory process due to rat sciatic nerve injury

Hepatic Osteodystrophy: The Mechanism of Bone Loss in Hepatocellular Disease and the Effects of Pamidronate Treatment

OBJECTIVES: The present study was designed to evaluate the bone phenotypes and mechanisms involved in bone disorders associated with hepatic osteodystrophy. Hepatocellular disease was induced by carbon tetrachloride (CCl4). In addition, the effects of disodium pamidronate on bone tissue were evaluated. METHODS: The study included 4 groups of 15 mice: a) C = mice subjected to vehicle injections; b) C+P = mice subjected to vehicle and pamidronate injections; c) CCl4+V = mice subjected to CCl4 and vehicle injections; and d) CCl4+P = mice subjected to CCl4 and pamidronate injections. CCl4 or vehicle was administered for 8 weeks, while pamidronate or vehicle was injected at the end of the fourth week. Bone histomorphometry and biomechanical analysis were performed in tibiae, while femora were used for micro-computed tomography and gene expression. RESULTS: CCl4 mice exhibited decreased bone volume/trabecular volume and trabecular numbers, as well as increased trabecular separation, as determined by bone histomorphometry and micro-computed tomography, but these changes were not detected in the group treated with pamidronate. CCl4 mice showed increased numbers of osteoclasts and resorption surface. High serum levels of receptor activator of nuclear factor-κB ligand and the increased expression of tartrate-resistant acid phosphatase in the bones of CCl4 mice supported the enhancement of bone resorption in these mice. CONCLUSION: Taken together, these results suggest that bone resorption is the main mechanism of bone loss in chronic hepatocellular disease in mice

Analysis of the effects of spaceflight and local administration of thrombopoietin to a femoral defect injury on distal skeletal sites

With increased human presence in space, bone loss and fractures will occur. Thrombopoietin (TPO) is a recently patented bone healing agent. Here, we investigated the systemic effects of TPO on mice subjected to spaceflight and sustaining a bone fracture. Forty, 9-week-old, male, C57BL/6 J were divided into 4 groups: (1) Saline+Earth; (2) TPO + Earth; (3) Saline+Flight; and (4) TPO + Flight (n = 10/group). Saline- and TPO-treated mice underwent a femoral defect surgery, and 20 mice were housed in space ("Flight") and 20 mice on Earth for approximately 4 weeks. With the exception of the calvarium and incisor, positive changes were observed in TPO-treated, spaceflight bones, suggesting TPO may improve osteogenesis in the absence of mechanical loading. Thus, TPO, may serve as a new bone healing agent, and may also improve some skeletal properties of astronauts, which might be extrapolated for patients on Earth with restraint mobilization and/or are incapable of bearing weight on their bones

Systemically alendronate was incorporated into dental tissues but did not cause morphological or mechanical changes in rats teeth

This study evaluated the effect of the systemic use of sodium alendronate in rats in vivo. Forty-five Wistar rats aged 36 to 42 days and weighing 200 to 230 g were randomly assigned to a control group (n = 20), which received distilled water, and an experimental group (n = 25), which received 2 weekly doses of 1 mg/kg of chemically pure sodium alendronate. The animals were killed after 60 days of treatment. The tibias were removed for analysis of bone mineral density by dual-energy X-ray absorptiometry (DXA). Then, the maxillary incisors were extracted for analysis of the mineralized dental tissues using fluorescence spectroscopy (FS), scanning electron microscopy (SEM), bright field microscopy (BFM), and cross-sectional microhardness (CSMH) testing. DXA and CSMH data were subjected to statistical analysis by Kruskal-Wallis test (5% significance level). The experimental group presented higher bone mineral density than the control group by DXA. FS analysis revealed presence of alendronate in the mineralized dental tissues of the specimens of the experimental group. Significant morphological differences were not found by SEM and BFM. Enamel and dentin (100 and 300 mu m from the dentinoenamel junction) CSMH data did not show significant difference between the control and experimental groups. Based on the obtained results, we conclude that while alendronate increased the bone mineral density and was incorporated into the mineralized dental tissues it did not cause significant alterations in the morphology and microhardness of rat incisor enamel and dentin. Microsc. Res. Tech. 75:12651271, 2012. (C) 2012 Wiley Periodicals, Inc.Brazilian Ministry of Healths Federal Agency for Support and Evaluation of Graduate Education (CAPES