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101.
Primary and revision total knee arthroplasty have become common orthopaedic procedures. The operating surgeon, at times, may be faced with a difficult surgical case due to soft tissue contractures or bone deformities. A review of multiple surgical techniques using soft tissue releases and osteotomies are presented including their potential complications. Although these techniques are aimed at the atypical operative case, the operating surgeon may utilize them for ‘routine’ exposures as well. Importance is focused on the functional integrity of the knee extensor mechanism. 相似文献
102.
Physics-Driven CFD Modeling of Complex Anatomical Cardiovascular Flows—A TCPC Case Study 总被引:5,自引:0,他引:5
Pekkan K de Zélicourt D Ge L Sotiropoulos F Frakes D Fogel MA Yoganathan AP 《Annals of biomedical engineering》2005,33(3):284-300
Recent developments in medical image acquisition combined with the latest advancements in numerical methods for solving the Navier-Stokes equations have created unprecedented opportunities for developing simple and reliable computational fluid dynamics (CFD) tools for meeting patient-specific surgical planning objectives. However, for CFD to reach its full potential and gain the trust and confidence of medical practitioners, physics-driven numerical modeling is required. This study reports on the experience gained from an ongoing integrated CFD modeling effort aimed at developing an advanced numerical simulation tool capable of accurately predicting flow characteristics in an anatomically correct total cavopulmonary connection (TCPC). An anatomical intra-atrial TCPC model is reconstructed from a stack of magnetic resonance (MR) images acquired in vivo. An exact replica of the computational geometry was built using transparent rapid prototyping. Following the same approach as in earlier studies on idealized models, flow structures, pressure drops, and energy losses were assessed both numerically and experimentally, then compared. Numerical studies were performed with both a first-order accurate commercial software and a recently developed, second-order accurate, in-house flow solver. The commercial CFD model could, with reasonable accuracy, capture global flow quantities of interest such as control volume power losses and pressure drops and time-averaged flow patterns. However, for steady inflow conditions, both flow visualization experiments and particle image velocimetry (PIV) measurements revealed unsteady, complex, and highly 3D flow structures, which could not be captured by this numerical model with the available computational resources and additional modeling efforts that are described. Preliminary time-accurate computations with the in-house flow solver were shown to capture for the first time these complex flow features and yielded solutions in good agreement with the experimental observations. Flow fields obtained were similar for the studied total cardiac output range (1–3 l/min); however hydrodynamic power loss increased dramatically with increasing cardiac output, suggesting significant energy demand at exercise conditions. The simulation of cardiovascular flows poses a formidable challenge to even the most advanced CFD tools currently available. A successful prediction requires a two-pronged, physics-based approach, which integrates high-resolution CFD tools and high-resolution laboratory measurements. 相似文献
103.
Ph. Wind A. Alves J. M. Chevallier C. Gillot J. P. Sales A. Sauvanet Ch. A. Cuénod V. Vilgrain P. H. Cugnenc V. Delmas 《Surgical and radiologic anatomy : SRA》1998,20(2):129-134
Summary Portal hypertension is characterised by the development of a collateral portocaval circulation. Among these venous reroutings, some are situated posteriorly in the left subphrenic compartment. These are the spontaneous splenorenal and gastrorenal anastomoses. Their incidence is estimated at around 16%. On the one hand, there are the direct shunts, which anastomose the spelling v. to the left renal v., of an anecdotal nature, and on the other the spontaneous indirect splenorenal shunts, characterised by the presence of a complete neurovascular pedicle traversing the gastrophrenic ligament. This relates to the gastric collateral v., which is connected to the left renal v. via the inferior v. of the left crus of the diaphragm and the middle capsular v., hence the name gastro-phreno-capsulorenal shunt. At an advanced stage of portal hypertension these splenorenal shunts may acquire a major caliber and behave like actual surgical shunts.
Anatomie des anastomoses veineuses spléno-rénale et gastro-rénales spontanées: revue de la littérature
Résumé L'hypertension portale se caractérise par le développement d'une circulation collatérale porto-cave. Parmi ces dérivations veineuses, certaines ont une topographie postérieure, localisée dans la loge sous-phrénique gauche. Ce sont les anastomoses spontanées splénorénales et gastro-rénales. Leur prévalence est estimée aux alentours de 16%. On distingue, d'une part, les shunts directs, qui anastomosent la v. splénique à la v. rénale gauche, de constatation anecdotique, non systématisés sur le plan anatomique ; d'autre part, les shunts splénorénaux spontanés indirects caractérisés par l'existence d'un pédicule complet vasculo-nerveux, cheminant dans le ligament gastro-phrénique. Il s'agit de la v. collatérale gastrique qui est reliée à la v. rénale gauche par l'intermédiaire de la v. inférieure du pilier gauche du diaphragme et de la v. capsulaire moyenne, d'où le nom de shunt gastro-phrénocapsulo-rénal. A un stade avancé de l'hypertension portale, ces shunts splénorénaux peuvent acquérir un calibre important et se comporter alors comme de véritables shunts chirurgicaux.相似文献
104.
Montes-Rodríguez CJ Alavez S Elder JH Haro R Morán J Prospéro-García O 《Neuroscience letters》2004,360(3):133-136
The human immunodeficiency virus (HIV) induces neuronal death, presumably by apoptosis. This effect may be triggered by the glycoprotein 120 (HIVgp120) released by HIV when infecting a cell, and mediated by tumor necrosis factor alpha (TNF), a pro-inflammatory cytokine. Both molecules, HIVgp120 and TNF, increase sleep when administered acutely in the brain. On the other hand, sleep deprivation increases the levels of several growth factors. In this context, we challenged rats with HIVgp120 or TNF simultaneously with sleep deprivation. Our results indicate that both HIVgp120 and TNF increase neuronal death in the rat cerebral cortex, but not hippocampus, and that this effect is completely prevented by total deprivation of sleep. These results suggest that acute total deprivation of sleep protects against the HIVgp120 and TNF deleterious effects. 相似文献
105.
Mahmoud S. El-Sayed Angelheart J.M. Rattu 《European journal of applied physiology》1996,73(1-2):88-92
This study examined the effect of prolonged submaximal exercise followed by a self-paced maximal performance test on cholesterol (T-Chol), triglycerides (TG), and high-density lipoprotein cholesterol (HDLC). Nine trained male athletes cycled at 70% of maximal oxygen consumption for 60 min, followed by a selfpaced maximal ride for 10 min. Venous blood samples were obtained at rest, at 30 and 60 min during submaximal exercise, and immediately after the performance test. Lactic acid, haematocrit (Hct), haemoglobin (Hb), T-Chol and TG were measured in the blood, while plasma was assayed for HDL-C. Plasma volume changes in response to exercise were calculated from Hct and Hb values and all lipid measurements were corrected accordingly. In order to ascertain the repeatability of lipid responses to exercise, all subjects were re-tested under identical testing conditions and experimental protocols. When data obtained during the two exercise trials were analysed by two-way ANOVA no significant differences (P > 0.05) between tests were observed. Consequently the data obtained during the two testing trials were pooled and analysed by one-way ANOVA. Blood lactic acid increased non-significantly (P > 0.05) during the prolonged submaximal test, but rose markedly (P < 0.05) following the performance ride. Lipid variables ascertained at rest were within the normal range for healthy subjects. ANOVA showed that blood T-Chol and TG were unchanged (P > 0.05), whereas HDL-C rose significantly (P < 0.05) in response to exercise. Post hoc analyses indicated that the latter change was due to a significant rise in HDL-C after the performance ride. It is concluded that apparent favourable changes in lipid profile variables occur in response to prolonged submaximal exercise followed by maximal effort, and these changes showed a good level of agreement over the two testing occasions. 相似文献
106.
J. Zweens Henny Frankena A. Reicher W. G. Zijlstra 《Pflügers Archiv : European journal of physiology》1980,385(1):71-77
The determination of D2O in biological fluids by means of infrared spectrometry was reinvestigated. When the temperature of a solution, containing D2O in the range from natural abundance to 5 ml·1–1 increases, its absorbance decreases and the wavenumber of maximum absorption shifts to a higher value. Both changes are linearly related to the change in temperature. Storage for 17 d in either glass or polyethylene tubes does not affect the D2O concentration. Purification of biological fluids by vacuum-sublimation removes all substances which also absorb at the O-D vibration band and the recovery of D2O from plasma and urine is complete. The partition ratio of D2O between plasma water and red cell water equals unity, and the same holds for plasma water and urine water over a wide range of urine flows and osmolalities. The arterial and urinary disappearance curves of D2O, measured over several days, both permit the calculation of the total amount of body water (V
bw), the daily water turn-over (F) and the half-time of water in the body (t
1/2), but the data derived from arterial disappearance curves are more precise. In 16 male mongrel dogs (25–32 kg body mass) the following results were obtained:V
bw=626±28 ml·kg–1,F=12.0±3.2% andt
1/2=6.21±1.78 d. 相似文献
107.
Harry S. Spaulding Jr. M.D.COL MC Lyndon E. Mansfield M.D.LTC MC Mark R. Stein M.D. John C. Sellner M.D. Daniel E. Gremillion M.D. 《The Journal of allergy and clinical immunology》1982,69(6):516-521
A double-blind modification of the intraesophageal acid perfusion challenge (Bernstein procedure) was performed in asthmatic subjects with and without gastroesophageal reflux, nonasthmatic subjects with reflux, and normal subjects. Conventional spirometric functions and total respiratory resistance (Rrs) were measured prior to and after the infusion. There were no changes in pulmonary functions except in the asthmatic subjects who had had a positive add challenge. The greatest changes occurred in Rrs, which increased significantly with reflux symptoms (p < 0.01) and decreased toward baseline (p < 0.05) when these symptoms were relieved with antacids. The response was even greater in asthmatic subjects who associated reflux symptoms with attacks of asthma. These results support previous findings that acid reflux symptoms could cause a bronchoconstrictive response in certain asthmatic patients. 相似文献
108.
Jacopo P. Mortola John T. Fisher Giuseppe Sant'Ambrogio 《Pflügers Archiv : European journal of physiology》1984,401(3):281-286
In an attempt to define the role of SARs on the breathing pattern and respiratory mechanics, we have studied adult rabbits
anaesthetised, supine and tracheostomised during air breathing (A), after SO2 breathing (200 ppm for a period long enough to abolish the apnea following lung inflation, 10–30 min) (S), and after bilateral
vagotomy (V). Tidal volume and inspiratory time increased, while breathing frequency decreased from A to V. The effects of
S depended upon the type of anaesthesia used, with a definite increase in volume and a drop in frequency in the urethane anaesthetized
animals and a trend toward opposite changes with barbiturate anaesthesia. Total and lung compliance increased and total pulmonary
resistance decreased from A to S; no further changes were observed with V. The combined changes in breathing pattern and mechanics
decreased the respiratory work per minute from A to V, suggesting that the primary concern of the vagal afferent information
is to regulation even with SO2 concentration up to 330 ppm for 30 min. From A to V the changes in breathing pattern and compliance were similar to those
observed in the adult. 相似文献
109.
110.
Previous studies demonstrated distinct cardiovascular patterns associated with threat and challenge appraisals for groups of participants. We extend these results by assessing whether appraisals continue to be associated with these cardiovascular response patterns within an individual as appraisals change. Participants completed four verbal mental arithmetic tasks for which they made appraisals before and after each task. Cardiac reactivity and total peripheral resistance (TPR) were calculated for the first and last minutes of each task, and the number of responses and percent correct were measured for each task. In line with our prediction, pretask appraisals were related to some task-related cardiac responses across the four tasks. In addition, task-related cardiovascular reactivity and behaviors both influenced appraisals following the task. Our findings suggest that an idiographic analysis of appraisals, cardiovascular physiology, and task-related behaviors provides a richer understanding of the appraisal process and reveals sex differences deserving further assessment. 相似文献