Este estudo foi financiado pela Boston Scientific Neuromodulação.

1. Introdução: A estimulação da medula espinhal, ou SCS, tem sido clinicamente aplicada desde 1967, quando o Dr. Norman Shealy primeiro implantaram eletrodos de estimulação sobre as colunas dorsal em uma tentativa de proporcionar um alívio para pacientes com dor crônica intratável (Shealy et al., 1967). SCS é a implementação clínica da Teoria Gate, que postula que a ativação de grandes nervos aferentes mielinizados que medeiam toque e sensações de pressão, pode inibir, ou &quot;fechar a porta&quot; na transmissão de sinais de dor para os centros superiores no cérebro (Melzack &amp; Wall , 1965). Tecnologia para o SCS tem melhorado ao longo das décadas, com equipamento de estimulação mais confiável melhor concebido para estimular as colunas dorsal evoluiu. Chave para estas melhorias tem sido uma maior compreensão da neuroanatomia e da neurofisiologia da medula espinhal relevantes para a estimulação elétrica clínico. Esse entendimento tem sido avançado pela modelagem computacional de SCS. Modelagem computacional de neurônios tem sido usada para compreender os mecanismos básicos para a estimulação neural desde modelo matemático de Hodgkin e Huxley foi descrita pela primeira vez (Hodgkin e Huxley, 1952). Atividade neural é modulada por campos elétricos aplicados como injeção de corrente intracelular e extracelular campos potenciais. Ranck qualitativamente discutido como as mudanças na tensão extracelular nas proximidades de um axônio causar algumas regiões da membrana do axônio para despolarizar e outros para hiperpolarizar (Ranck, 1975). Um modelo computacional para SCS foi inicialmente desenvolvido por Coburn e Sin (Coburn, 1980) e foi significativamente reforçada por Holsheimer e colegas, começando com Struijk e desenvolvimento Holsheimer de um modelo tridimensional do campo SCS (Holsheimer e Struijk, 1988). Seu modelo computacional estima o efeito de parâmetros anatômicos sobre os limiares de fibras da coluna dorsal (Struijk et al., 1992), previu a localização potencial de excitação nas fibras da raiz dorsal (Struijk et al., 1993b), e analisaram o efeito da CSF espessura (Struijk et al, 1993a.) com validações clínicas (He et al, 1994;. Holsheimer et al, 1995a;.. Holsheimer et al, 1994). O modelo contribuiu significativamente para a concepção do projeto levar a estimulação, sugerindo parâmetros ótimos para o tamanho do contato e espaçamento (Holsheimer e Struijk, 1992; Holsheimer e Wesselink, 1997), para favorecer a estimulação preferencial de fibras da coluna dorsal sobre as fibras da raiz (Holsheimer et al,. 1995b). 2. Métodos: Definição do modelo matemático Um elemento finito modelo matemático (FEM) foi criado da medula espinhal torácica baixa e seu ambiente circundante. O modelo FEM consistia de matéria medula espinhal branco e cinza, líquido cefalorraquidiano, dura, o tecido do espaço epidural, o osso vertebral, e dois leva Multicontact cilíndrico. Cada ligação, composta de oito cilíndrica de platina-irídio contatos (domínios condução, comprimento 3 mm e 1,25 mm de diâmetro), separados por um milímetro de comprimento isolante de polímero (não-realização de domínios, comprimento 1mm). Os eletrodos foram posicionados dorsalmente, no topo da dura-máter, e simétrico, 1mm para cada lado da linha média da medula espinhal. No modelo, a &quot;espessura&quot; da camada de líquido cefalorraquidiano entre os contatos ea superfície dorsal da medula espinhal (DCSF) foi especificado para ser 3,2 mm. A geometria do modelo é ilustrada na Figura 1A e resistividades elétricas são apresentadas na Tabela I, os valores que vem predominantemente da literatura (Holsheimer, 2002;. Wesselink et al, 1999). O volume foi malha com mais de 1 milhão de nós, com uma malha de alta densidade na região próxima ao local onde estão localizados os eletrodos, conforme ilustrado na Figura 1B. <img src="/files/ftp_upload/2443/2443fig1.jpg" alt="Figura 1" /> Figura 1. Representação da malha da FEM para a medula espinhal e levar Multicontact. (A) Componentes e estrutura do modelo. (B) de malha Modelo - apenas a parte de alta densidade é mostrado. A malha foi dividido em seções de densidade de nós variável: perto os contatos (≤ M 300); isolante, dura ea medula espinhal (M ≤ 750); espaço epidural (≤ 3000 mm); e osso vertebral (≤ 5000 mm). <img src="/files/ftp_upload/2443/2443table1.jpg" alt="Tabela 1" /> Tabela 1 valores de resistividade dos domínios FEM (Holsheimer, 2002;. Wesselink et al, 1999). E modificação (espaço epidural) para combinar com dados clínicos. A geometria da medula espinhal (Figura 2) foi criado usando uma combinação de recursos de fontes literatura relevante. A secção transversal do cabo foi derivado de Kameyama et al, ea trajetória da raiz dorsal (DR) de Struijk et al foi adotado (Kameyama et al, 1996;... Struijket al., 1993b). Coluna dorsal (DC) fibras foram colocados em grade regular de (200um para a direção médio-lateral e direção dorsoventral 100um; ver Figura 2A) e projetado na direção rostro-caudal. Cada DR foi modelada como fibra de &#39;mãe&#39; de maior diâmetro ligado a fibras &#39;filha&#39; bifurcado de menor diâmetro (Fig. 2B). <img src="/files/ftp_upload/2443/2443fig2.jpg" alt="Figura 2" /> Figura 2. Estrutura do modelo de medula espinhal. (A) visão transacional da medula espinhal e localização das fibras da coluna dorsal. (B) raízes dorsais são compostos de uma fibra de mãe e filha fibras bifurcada. A trajetória da fibra mãe foi digitalizado a partir Struijk 1993. (C) visão tridimensional da medula espinhal e das fibras DR. Investigação modelo Uma vez que os eletrodos foram posicionados dentro do modelo, os dois tipos de estimuladores foram implementadas, definindo as correntes de dois contatos paralelos. Para um sistema de fonte única, havia três métodos possíveis para fornecer corrente: a. o contato mais à esquerda tem todas as correntes; b. os dois contatos de cada entregar 50% da corrente; c. o contato mais à direita fornece todos os atuais. Notamos aqui que a impedância dos dois contatos é assumido ser igual, embora isto seja pouco provável que seja verdade na aplicação clínica. Para o sistema de múltiplas fontes, cada contato foi definida a ter sua própria fonte atual controlável em 1% incremental mudanças em curso entre os contatos. Em outras palavras, se a corrente total entregue aos dois contatos é 10mA, no sistema de múltiplas fontes a corrente a cada contato foi especificada a qualquer fração do total, enquanto a soma das correntes através de cada contato 10mA iguais. Por exemplo, o contato mais à esquerda pode entregar 6,8 mA, onde o contato mais à direita, então, entregar 3,2 mA. Para o sistema de múltiplas fontes, 100 fracionária divide de corrente foram programados desta forma. Para calcular a região de ativação dentro das colunas dorsal de cada sistema, uma análise da função de ativação foi realizada. A função de ativação é uma aproximação da mudança no potencial transmembrana quando a corrente estimulando extracelular é aplicada ao tecido neural para um dado eletrodo ea geometria da fibra. A região de ativação foi definido como o locus de fibras no modelo onde a função de ativar (ou simplesmente diferença de tensões segundo ao longo axônio) ultrapassou um determinado limite (ex. 0.1mV/mm2). O ponto central da estimulação foi definido e calculado como o centróide geométrico da região 3-dimensional de ativação. Para determinar a amplitude de estimulação, os dois contatos foram especificados para ser catodos (50% e 50% potencial negativo em dois contactos) em uma configuração monopolar (fontes atuais entregue com densidade de corrente equivalente a partir das fronteiras do modelo). A amplitude de estimulação foi, então, iterativamente aumentada até a primeira fibra ativada foi observado (isso foi sempre uma fibra coluna dorsal). Esta primeira ativação foi assumida para correlacionar primeira percepção de parestesia por um paciente no contexto clínico. No modelo, a corrente foi depois aumentada para 1,4 * (mA para ativar primeira fibra) eo centróide da região resultante de ativação foi calculado. Centróides de todas as etapas de direcção (100:0 a 0:100) foram calculados com amplitude determinado na etapa anterior. Resolução de variação média centróide foi gama localização centróide dividida por etapas atuais. 3. Resultado: Quando direcção estimulação mediolaterally entre as derivações dual, o modelo computacional que prevê um dispositivo com fontes independentes de corrente para cada contato pode ter como alvo pontos mais centrais de estimulação na coluna dorsal que um sistema de fonte única (100 vs 3). Como resultado disso, a resolução do ajuste do ponto central de estimulação é de 30 hm com um sistema de múltiplas fontes, um aumento de 50 vezes comparado ao aproximada de uma única fonte de sistemas (ver Figura 3). <img src="/files/ftp_upload/2443/2443fig3.jpg" alt="Figura 3" /> Figura 3. O modelo computacional faz as seguintes previsões. A. configuração levar Dual: 2,0 mm entre a separação conduz com estimulação monopolo. Dispositivos de origem B. Único que fornecer uma única fonte de poder compartilhado para todos os contatos pode ter como alvo três pontos centrais de estímulo ao deslocar a estimulação mediolaterally (um tamanho de passo de 1 mm, em média, com 2 separação levar mm). C: Um dispositivo com uma fonte de alimentação dedicada para cada contato pode atingir 100 pontos centrais lateralmente na coluna dorsal quando fractionalizing corrente em incrementos de 1%, ou 10 pontos centrais quando fractionalizing em incrementos de 10% (um tamanho de passo de 0,02 mm para 1% passos e 0,2 mm para as etapas 10% em média).

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Os autores são funcionários da Boston Scientific Neuromodulação.

A capacidade de estimulação regiões centro na coluna dorsal com alta resolução pode permitir uma melhor optimização de parestesia dor sobreposição de pacientes. Ou seja, em um determinado paciente, a região de ativação nas colunas dorsal podem ser focalizados para maximizar a cobertura de áreas dolorosas, minimizando efeitos colaterais (devido à estimulação de fibras indesejáveis, que podem gerar parestesia em locais indesejáveis ​​ou criar motora ou autonômica efeitos).

<ul><li> NEURÔNIO ( <a href="http://www.neuron.yale.edu">http://www.neuron.yale.edu</a> ) </li><li> ANSYS (Canonsburg, PA, <a href="http://www.ansys.com">http://www.ansys.com</a> ) </li><li> Matlab (Natick, MA, <a href="http://www.mathworks.com">http://www.mathworks.com</a> ) </li></ul>

dorsal column steerability with dual parallel leads using dedicated power sources:  a computational model

Na estimulação da medula espinal (SCS), a concordância de estimulação induzida por parestesia dolorosa mais regiões do corpo é uma condição necessária para a eficácia terapêutica. Uma vez que os padrões de dor do paciente pode ser único, uma configuração de estímulo comum é a colocação de dois fios em paralelo no espaço epidural dorsal. Esta construção proporciona flexibilidade na condução estimulação atual mediolaterally sobre a coluna dorsal para conseguir uma melhor dor parestesia se sobrepõem. Usando um modelo matemático com uma distribuição precisa de fibra de diâmetro, estudamos a possibilidade de paralelo dupla leva para orientar a estimulação entre contatos adjacentes em paralelo dupla leva usando (1) um sistema de fonte única, e (2) um sistema multi-fonte, com um dedicada fonte de corrente para cada contato. O modelo de volume condutor de um cabo de baixa espinhal torácica com epidural posicionada paralela dupla (2 separação mm) leva percutânea foi criado, eo campo elétrico foi calculada usando ANSYS, uma ferramenta de modelagem finita elemento. A função de ativação por 10 fibras hum foi calculada como a segunda diferença do potencial extracelular ao longo dos nós de Ranvier sobre as fibras nervosas na coluna dorsal. O volume de ativação (VOA) eo ponto central da VOA foram computados usando um determinado limite da função de ativação. O modelo comparou os resultados de campo com direção única fonte de energia versus sistemas dedicados fonte de dupla leva oito contato estimulação. O modelo previu que o sistema multi-source pode direcionar mais pontos centrais de estimulação na coluna dorsal que um sistema de fonte única (100 vs 3) ea etapa de direcção, para a direção médio-lateral é de 0,02 mm para fonte de sistemas multi-vs 1 mm para sistemas de fonte única, uma melhoria de 50 vezes. A capacidade de estimulação regiões centro na coluna dorsal com alta resolução pode permitir uma melhor optimização de parestesia dor sobreposição de pacientes.

Watch this Scientific Journal Video about Dorsal Column Steerability with Dual Parallel Leads using Dedicated Power Sources:  A Computational Model at JoVE.com

Dorsal Column Steerability with Dual Parallel Leads using Dedicated Power Sources:  A Computational Model

Usando um modelo matemático de estimulação da medula espinhal, descobrimos que um sistema multi-source com fontes de energia independente para cada contato pode direcionar mais pontos centrais de estimulação na coluna dorsal (100 vs 3) e tem 50 vezes mais resolução de direção de campo ( 0,02 milímetros vs 1mm) do que um sistema de fonte única.

Dirigibilidade coluna dorsal com terminais paralelo duplo usando fontes de energia dedicados: um modelo computacional

In spinal cord stimulation (SCS), concordance of stimulation-induced paresthesia over painful body regions is a necessary condition for therapeutic ...

dorsal-column-steerability-with-dual-parallel-leads-using-dedicated

Research

JoVE Journal

Medicine

11.8K visualizações.  Neuromodulation. Usando um modelo matemático de estimulação da medula espinhal, descobrimos que um sistema multi-source com fontes de energia independente para cada contato pode direcionar mais pontos centrais de estimulação na coluna dorsal (100 vs 3) e tem 50 vezes mais resolução de direção de campo ( 0,02 milímetros vs 1mm) do que um sistema de fonte única.

Vídeo: Dorsal Column Steerability with Dual Parallel Leads using Dedicated Power Sources:  A Computational Model

A Novel Capsulorhexis Technique Using Shearing Forces with Cystotome

Purpose:
To demonstrate a capsulorhexis technique using predominantly shearing forces with a cystotome on a virtual reality simulator and on a human eye.
Method:
Our technique involves creating the initial anterior capsular tear with a cystotome to raise a flap. The flap left unfolded on the lens surface. The cystotome tip is tilted horizontally and is engaged on the flap near the leading edge of the tear. The cystotome is moved in a circular fashion to direct the vector forces. The loose flap is constantly swept towards the centre so that it does not obscure the view on the tearing edge.
Results:
Our technique has the advantage of reducing corneal wound distortion and subsequent anterior chamber collapse. The capsulorhexis flap is moved away from the tear leading edge allowing better visualisation of the direction of tear. This technique offers superior control of the capsulorhexis by allowing the surgeon to change the direction of the tear to achieve the desired capsulorhexis size.
Conclusions:
The EYESI Surgical Simulator is a realistic training platform for surgeons to practice complex capsulorhexis techniques. The shearing forces technique is a suitable alternative and in some cases a far better technique in achieving the desired capsulorhexis.

This video demonstrates a novel capsulorhexis technique in modern cataract surgery. Capsulorhexis is the most difficult and important part of phacoemulsification surgery.

A Técnica Capsulorhexis Novel Usando as forças de cisalhamento com Cystotome

Purpose:
To demonstrate a capsulorhexis technique using predominantly shearing forces with a cystotome on a virtual reality simulator and on a human eye....

Medicina

In vivo Dual Substrate Bioluminescent Imaging

Our understanding of how and when breast cancer cells transit from established primary tumors to metastatic sites has increased at an exceptional rate since the advent of in vivo bioluminescent imaging technologies 1-3. Indeed, the ability to locate and quantify tumor growth longitudinally in a single cohort of animals to completion of the study as opposed to sacrificing individual groups of animals at specific assay times has revolutionized how researchers investigate breast cancer metastasis. Unfortunately, current methodologies preclude the real-time assessment of critical changes that transpire in cell signaling systems as breast cancer cells (i) evolve within primary tumors, (ii) disseminate throughout the body, and (iii) reinitiate proliferative programs at sites of a metastatic lesion. However, recent advancements in bioluminescent imaging now make it possible to simultaneously quantify specific spatiotemporal changes in gene expression as a function of tumor development and metastatic progression via the use of dual substrate luminescence reactions. To do so, researchers take advantage for two light-producing luciferase enzymes isolated from the firefly (Photinus pyralis) and sea pansy (Renilla reniformis), both of which react to mutually exclusive substrates that previously facilitated their wide-spread use in in vitro cell-based reporter gene assays 4. Here we demonstrate the in vivo utility of these two enzymes such that one luminescence reaction specifically marks the size and location of a developing tumor, while the second luminescent reaction serves as a means to visualize the activation status of specific signaling systems during distinct stages of tumor and metastasis development. Thus, the objectives of this study are two-fold. First, we will describe the steps necessary to construct dual bioluminescent reporter cell lines, as well as those needed to facilitate their use in visualizing the spatiotemporal regulation of gene expression during specific steps of the metastatic cascade. Using the 4T1 model of breast cancer metastasis, we show that the in vivo activity of a synthetic Smad Binding Element (SBE) promoter was decreased dramatically in pulmonary metastasis as compared to that measured in the primary tumor 4-6. Recently, breast cancer metastasis was shown to be regulated by changes within the primary tumor microenvironment and reactive stroma, including those occurring in fibroblasts and infiltrating immune cells 7-9. Thus, our second objective will be to demonstrate the utility of dual bioluminescent techniques in monitoring the growth and localization of two unique cell populations harbored within a single animal during breast cancer growth and metastasis.

In vivo Dual Substrate Bioluminescent Imaging

Herein we describe the methods to construct, visualize, and quantify the bioluminescent reactions of both firefly and renilla luciferase enzymes expressed in metastatic breast cancer cells during their growth and metastasis in vivo.

In vivo dupla Substrato Bioluminescent imagem

Our understanding of how and when breast cancer cells transit from established primary tumors to metastatic sites has increased at an exceptional rate ...

Deep Neuromuscular Blockade Leads to a Larger Intraabdominal Volume During Laparoscopy

Shoulder pain is a commonly reported symptom following laparoscopic procedures such as myomectomy or hysterectomy, and recent studies have shown that lowering the insufflation pressure during surgery may reduce the risk of post-operative pain. In this pilot study, a method is presented for measuring the intra-abdominal space available to the surgeon during laproscopy, in order to examine whether the relaxation produced by deep neuromuscular blockade can increase the working surgical space sufficiently to permit a reduction in the CO2 insufflation pressure. Using the laproscopic grasper, the distance from the promontory to the skin is measured at two different insufflation pressures: 8 mm Hg and 12 mm Hg. After the initial measurements, a neuromuscular blocking agent (rocuronium) is administered to the patient and the intra-abdominal volume is measured again. Pilot data collected from 15 patients shows that the intra-abdominal space at 8 mm Hg with blockade is comparable to the intra-abdominal space measured at 12 mm Hg without blockade. The impact of neuromuscular blockade was not correlated with patient height, weight, BMI, and age. Thus, using neuromuscular blockade to maintain a steady volume while reducing insufflation pressure may produce improved patient outcomes.

This article presents a method for measuring the working abdominal volume during laproscopic myomectomy using the surgical grasper, and applies this technique to obtain pilot data on whether deep neuromuscular blockade (NMB) can enable the use of lower insufflation pressure. Reduced insufflation pressure during laproscopic surgery has been shown to reduce post-operative pain, and thus the use of NMB during surgery may enable improved patient outcomes.

Bloqueio Neuromuscular profunda leva a um volume maior intra-abdominal durante a laparoscopia

Shoulder pain is a commonly reported symptom following laparoscopic procedures such as myomectomy or hysterectomy, and recent studies have shown that ...

Ischemic Tissue Injury in the Dorsal Skinfold Chamber of the Mouse: A Skin Flap Model to Investigate Acute Persistent Ischemia

Despite profound expertise and advanced surgical techniques, ischemia-induced complications ranging from wound breakdown to extensive tissue necrosis are still occurring, particularly in reconstructive flap surgery. Multiple experimental flap models have been developed to analyze underlying causes and mechanisms and to investigate treatment strategies to prevent ischemic complications. The limiting factor of most models is the lacking possibility to directly and repetitively visualize microvascular architecture and hemodynamics. The goal of the protocol was to present a well-established mouse model affiliating these before mentioned lacking elements. Harder et al. have developed a model of a musculocutaneous flap with a random perfusion pattern that undergoes acute persistent ischemia and results in ~50% necrosis after 10 days if kept untreated. With the aid of intravital epi-fluorescence microscopy, this chamber model allows repetitive visualization of morphology and hemodynamics in different regions of interest over time. Associated processes such as apoptosis, inflammation, microvascular leakage and angiogenesis can be investigated and correlated to immunohistochemical and molecular protein assays. To date, the model has proven feasibility and reproducibility in several published experimental studies investigating the effect of pre-, peri- and postconditioning of ischemically challenged tissue.

The window of the murine dorsal skinfold chamber presented visualizes a zone of acute persistent ischemia of a musculocutaneous flap. Intravital epi-fluorescence microscopy permits for direct and repetitive assessment of the microvasculature and quantification of hemodynamics. Morphologic and hemodynamic results can further be correlated with histological and molecular analyses.

Lesão tecido isquêmico na Skinfold Câmara do mouse Dorsal: Um Modelo retalho de pele para investigar aguda isquemia persistente

Despite profound expertise and advanced surgical techniques, ischemia-induced complications ranging from wound breakdown to extensive tissue necrosis are ...

Using Saccadometry with Deep Brain Stimulation to Study Normal and Pathological Brain Function

The oculomotor system involves a large number of brain areas including parts of the basal ganglia, and various neurodegenerative diseases including Parkinson's and Huntington's can disrupt it. People with Parkinson's disease, for example, tend to have increased saccadic latencies. Consequently, the quantitative measurement of saccadic eye movements has received considerable attention as a potential biomarker for neurodegenerative conditions. A lot more can be learned about the brain in both health and disease by observing what happens to eye movements when the function of specific brain areas is perturbed. Deep brain stimulation is a surgical intervention used for the management of a range of neurological conditions including Parkinson's disease, in which stimulating electrodes are placed in specific brain areas including several sites in the basal ganglia. Eye movement measurements can then be made with the stimulator systems both off and on and the results compared. With suitable experimental design, this approach can be used to study the pathophysiology of the disease being treated, the mechanism by which DBS exerts it beneficial effects, and even aspects of normal neurophysiology.

This paper describes the use of quantitative measurement of eye movements in conjunction with stimulation of focal areas of the deep brain in order to study physiology, pathophysiology, and the mechanisms of deep brain stimulation.

Usando Saccadometry com Estimulação Cerebral Profunda para estudar normal e patológico função cerebral

The oculomotor system involves a large number of brain areas including parts of the basal ganglia, and various neurodegenerative diseases including ...

Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and drugs. It is widely used in many studies on the physiological functions of vascular smooth muscle, the pathogenesis of vascular diseases such as hypertension, and the development of smooth muscle relaxant drugs. The mouse is a widely used model animal with a large pool of disease models and genetically modified strains. We introduced this method to measure the isometric contraction of mouse mesenteric artery in detail. A 1.4-mm segment of mouse mesenteric resistance artery was isolated and mounted on a myograph chamber by passing two steel wires through its lumen. After equilibration and normalization steps, the vessel segment was potentiated by a high-K+ solution twice prior to the contraction assay. As an example of the application of this method in drug development, we measured the relaxant effect of a novel natural substance, neoliensinine, isolated from a Chinese herb, embryos of the lotus seed (Nelumbo nucifera Gaertn.) on mouse mesenteric arteries. The vessel segments mounted on the myograph chamber were stimulated with a high-K+ solution. When the force tension reached a stable sustained phase, cumulative doses of neoliensinine were added to the chamber. We found that neoliensinine had a dose-dependent relaxant effect on smooth muscle contraction, thus suggesting that it bears potential activity against hypertension. In addition, as the vessel segment can survive at least 4 hours after mounting and maintain contractility induced by the high-K+ solution for many times, we suggest that the wire myograph system may be used for the time-consuming process of drug screening.

The wire myograph technique is used to investigate vascular smooth muscle functions and screen new drugs. We report a detailed protocol for measuring the isometric contractility of the mouse mesenteric artery and for screening new relaxants of vascular smooth muscle.

Medição de contratilidade isométrica da artéria mesentérica Mouse usando fio miografia

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and ...

Murine Model of Central Venous Stenosis using Aortocaval Fistula with an Outflow Stenosis

Central venous stenosis is an important entity contributing to arteriovenous fistula (AVF) failure. A murine AVF model was modified to create a partial ligation of the inferior vena cava (IVC) in the outflow of the fistula, mimicking central venous stenosis. Technical aspects of this model are introduced. The aorta and IVC are exposed, following an abdominal incision. The infra-renal aorta and IVC are dissected for proximal clamping, and the distal aorta is exposed for puncture. The IVC at the midpoint between the left renal vein and the aortic bifurcation is carefully dissected to place an 8-0 suture beneath the IVC. After clamping the aorta and IVC, an AVF is created by puncturing the infra-renal aorta through both walls into the IVC with a 25 G needle, followed by ligating a 22 G intra-venous (IV) catheter and IVC together. The catheter is then removed, creating a reproducible venous stenosis without occlusion. The aorta and IVC are unclamped after confirming primary hemostasis. This novel model of central vein stenosis is easy to perform, reproducible, and will facilitate studies on AVF failure.

An aortocaval fistula was created by puncturing the murine infra-renal aorta through both walls into the inferior vena cava and was followed by creation of a stenosis in its outflow via partial ligation of the inferior vena cava. This reproducible model can be used to study central venous stenosis.

Modelo murino de estenose venosa central usando fístula Aortocaval com estenose de saída

Central venous stenosis is an important entity contributing to arteriovenous fistula (AVF) failure. A murine AVF model was modified to create a partial ...

A Porcine Corneal Endothelial Organ Culture Model Using Split Corneal Buttons

Experimental research on corneal endothelial cells is associated with several difficulties. Human donor corneas are scarce and rarely available for experimental investigations as they are normally needed for transplantation. Endothelial cell cultures often do not translate well to in vivo situations. Due to the biostructural characteristics of non-human corneas, stromal swelling during cultivation induces substantial corneal endothelial cell loss, which makes it difficult to perform cultivation for an extended period of time. Deswelling agents such as dextran are used to counteract this response. However, they also cause significant endothelial cell loss. Therefore, an ex vivo organ culture model not requiring deswelling agents was established. Pig eyes from a local slaughterhouse were used to prepare split corneal buttons. After partial corneal trephination, the outer layers of the cornea (epithelium, bowman layer, parts of the stroma) were removed. This significantly reduces corneal endothelial cell loss induced by massive stromal swelling and Descemet&#39;s membrane folding throughout longer cultivation periods and improves general preservation of the endothelial cell layer. Subsequent complete corneal trephination was followed by the removal of the split corneal button from the remaining eye bulb and cultivation. Endothelial cell density was assessed at follow-up times of up to 15 days after preparation (i.e., days 1, 8, 15) using light microscopy. The preparation technique used allows a better preservation of the endothelial cell layer enabled by less stromal tissue swelling, which results in slow and linear decline rates in split corneal buttons comparable to human donor corneas. As this standardized organo-typically cultivated research model for the first time allows a stable cultivation for at least two weeks, it is a valuable alternative to human donor corneas for future investigations of various external factors with regards to their effects on the corneal endothelium.

Here, a step-by-step protocol for the preparation and cultivation of porcine split corneal buttons is presented. As this organo-typically cultivated organ culture model shows cell death rates within 15 days, comparable to human donor corneas, it represents the first model allowing long-term cultivation of non-human corneas without adding toxic dextran.

Um modelo de cultura de órgão endotelial corneano porcina usando Split córnea botões

Experimental research on corneal endothelial cells is associated with several difficulties. Human donor corneas are scarce and rarely available for ...

In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy

Several hip pathologies have been attributed to abnormal morphology with an underlying assumption of aberrant biomechanics. However, structure-function relationships at the joint level remain challenging to quantify due to difficulties in accurately measuring dynamic joint motion. The soft tissue artifact errors inherent in optical skin marker motion capture are exacerbated by the depth of the hip joint within the body and the large mass of soft tissue surrounding the joint. Thus, the complex relationship between bone shape and hip joint kinematics is more difficult to study accurately than in other joints. Herein, a protocol incorporating computed tomography (CT) arthrography, three-dimensional (3D) reconstruction of volumetric images, dual fluoroscopy, and optical motion capture to accurately measure the dynamic motion of the hip joint is presented. The technical and clinical studies that have applied dual fluoroscopy to study form-function relationships of the hip using this protocol are summarized, and the specific steps and future considerations for data acquisition, processing, and analysis are described.

In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy

Dual fluoroscopy accurately captures in vivo dynamic motion of human joints, which can be visualized relative to reconstructed anatomy (e.g., arthrokinematics). Herein, a detailed protocol to quantify hip arthrokinematics during weight-bearing activities of daily living is presented, including the integration of dual fluoroscopy with traditional skin marker motion capture.

In vivo Quantificação da Artrokinematics de Quadril durante atividades dinâmicas de peso usando fluoroscopia dupla

Several hip pathologies have been attributed to abnormal morphology with an underlying assumption of aberrant biomechanics. However, structure-function ...

Modified Posterior Vertebral Column Resection for Patients with Thoracolumbar Kyphotic Deformity

Old compression vertebrae fracture or congenital kyphoscoliosis with abnormal vertebral body development and other diseases that invade the spine may cause severe thoracolumbar kyphotic deformity, often accompanied by intractable low back pain or compression of the spinal cord, leading to severe neurological symptoms or even paralysis. If conservative treatment cannot relieve the symptoms or correct the deformities, surgical treatment is usually needed. For severe kyphotic deformity, reconstruction of the physiological curvature and rigid fixation determine the prognosis of the patients. Osteotomy and orthopedics are the standard procedure for deformities with severe compression of the front and middle column, but the trauma to the patients is high, with a long operation time and massive blood loss. To avoid these disadvantages, we have developed a modified technique to remove the diseased vertebra unilaterally. In this technique, we use a modified trephine to resect the vertebral columns like in the pedicle screw technique by adding a locking instrument that can restrict the trephine to lower the risk of osteotomy and shorten the surgery time and blood loss.

We describe a modified technique for resecting the posterior vertebral column unilaterally based on a modified trephine for patients with thoracolumbar kyphotic deformity.

Ressecção da Coluna Vertebral Posterior Modificada para Pacientes com Deformidade Cifótica Toracolombar

Old compression vertebrae fracture or congenital kyphoscoliosis with abnormal vertebral body development and other diseases that invade the spine may ...