Pseudoaneurysm of profunda femoris artery following dynamic hip screw fixation for intertrochanteric femoral fracture

Dynamic hip screw fixation is a commonly performed procedure for internal fixation of intertrochanteric femoral fractures.Arterial injury following the operative fixation is a rare but serious event.We...     

Assessing the Use of the “Opening Angle Method” to Enforce Residual Stresses in Patient-Specific Arteries

Numerical and analytical studies on cylindrical geometries have shown the relevance of accounting for residual stresses in arterial modeling. However, multiple difficulties, both geometrical and numerical, arise when enforcing residual stresses in patient-specific arteries. This is the reason of the few simulations that have been developed on this kind of geometries. In this paper we present a methodology that allows to include residual stresses in arbitrary geometries. Since it is not necessary to know the opened configuration of the artery, it makes it possible to take advantage of non-invasive image acquisition techniques such as CT or MRI to create customized arterial models. A simplified initial strain field showing its accuracy when applied to actual in vivo closed geometries is hypothesized from an opening angle experiment. In addition to residual stresses, the anisotropic hyperelastic and multilayered nature of the arterial tissue was accounted for the simulations of the behavior of a human coronary and iliac arteries. Results show the relevance of considering all these features for getting realistic results and the relative accuracy of using approximate solutions of residual stresses in patient-specific arterial simulations.     

The effect of pressure drop stabilization in arteries during variations in blood flow rate

The aim of this study was to clear up whether the flow-induced dilation of arteries is sufficient to ensure invariability of pressure drop along these vessels under many-fold increase in blood flow rate. In anaesthetized rats an arteriovenous shunt was constructed by connecting the saphenous artery and the femoral vein. Resistance of the shunt was changed by a device creating either rectangular flow pulses of different amplitude or slow linear ramps of flow rate. Pressure drop along the arterial cascade, from the aortic arch up to distal saphenous artery, was recorded and the steady-state flow-pressure drop relationship was determined. At low flow rates (< 0.25–0.3 ml min^-1) the pressure drop rose proportionally to flow, i.e. as in a system of ordinary tubes with non-regulated diameter. In contrast, at higher flow rates (up to 1.5 ml min^-1) the pressure drop either remained unchanged under 3- to 5-fold increases of flow rate or rose far less than the flow. Thus, the pressure drop stabilization effect has been evidenced. The threshold of this effect was about 0.3 ml min^-1, corresponding to the ‘resting’ flow in the saphenous artery, i.e. the narrowest of all the cascade vessels. This coincidence suggests that the pressure drop stabilization is determined by the flow-induced dilation mainly of this artery.     

舌动脉临床解剖学研究

目的 获得舌动脉的临床解剖学资料,为涉及舌动脉的临床应用提供解剖依据.方法 分别在头颈血管的64层螺旋CT血管成像(64-slices spiral computed tomography angiography,CTA)和成人头颈部标本上观察舌动脉的起源、形态、走行,测量舌动脉与颈动脉分叉、舌骨大角的关系,并对其结果进行对比分析.结果 舌动脉主要起源于颈外动脉(CTA组,74.4%;标本组,80%),其次起源于面动脉(CTA组,23.1%;标本组,20%);起源于甲状腺上动脉者少见,在CTA组占2.5%,在标本组中未发现舌动脉起源于甲状腺上动脉.舌动脉走行变异较大,在舌骨大角处较恒定,在CTA组舌动脉在舌骨大角上(2.32±1.29)mm、下(2.00±1.68)mm范围内,近似平行于舌骨大角水平向前入舌.在CTA组和标本组,舌动脉起始点到颈动脉分叉水平和舌骨大角尖端水平之间距离分别为(12.93±7.36)mm、(10.40±5.75)mm;(14.80±6.18)mm、(8.35±5.44)mm.结论 舌动脉在CTA上能清楚地显示,并能获得生理状态下的解剖学资料.     

Traumatic Axillary Artery Dissection with Radial Artery Embolism

This report describes a case of pathologically proven traumatic arterial dissection, presenting as complete occlusion of the axillary artery with radial artery embolism. Occlusion of the axillary artery by traumatic dissection mimicked transection and radial artery embolism mimicked congenital absence of the radial artery on the initial angiogram, but these were correctly diagnosed with the following sonogram.     

Modulation of sympathetic neurotransmission by neuropeptide Y Y2 receptors in rats and guinea pigs

We have investigated the effect of the Y₂ receptor agonist (Y₂ agonist; N-acetyl [Leu^28,31] NPY 24-36), on contractions evoked by transmural electrical stimulation of sympathetic nerves of isolated arteries from a range of vascular beds in rats and guinea pigs. Contractions evoked by transmural stimulation of the rat renal, mesenteric and femoral arteries were significantly attenuated in the presence of the Y₂ agonist. In these arteries, contractions were significantly inhibited in the presence of an α-adrenoceptor antagonist (76–97%). So we conclude that these responses were primarily mediated by noradrenaline and that the Y₂ agonist attenuates the release of noradrenaline via presynaptic Y₂ receptors. Contractions of the rat carotid artery were not attenuated by the Y₂ agonist but were completely abolished in the presence of an α-adrenoceptor antagonist suggesting that in this artery the Y₂ agonist has no effect on release of noradrenaline. In the guinea pig, carotid arteries contractions evoked by transmural nerve stimulation were attenuated in the presence of the Y₂ agonist and inhibited by an α-adrenoceptor antagonist 75–87% suggesting that the Y₂ agonist attenuates the release of noradrenaline via presynaptic Y₂ receptors in this vessel. In the guinea pig femoral artery contractions evoked by transmural stimulation were not modified in the presence of the Y₂ agonist but were completely abolished in the presence of an α-adrenoceptor antagonist. This suggests that the Y₂ agonist does not modify noradrenaline release in this vessel. Contractions of the guinea pig mesenteric artery were significantly potentiated by the Y₂ agonist, possibly by potentiation of neuropeptide Y (NPY) at the Y₁ receptor. The Y₁ antagonist inhibited more than 70 % of the response, indicating that the majority of the contraction was mediated by NPY. The current study demonstrates heterogeneity of neurotransmitter substances in sympathetic nerves supplying vascular beds within and across species and in subsequent functional response.Supported by the National Health and medical Research Council of Australia.     

Fluid and solid mechanical implications of vascular stenting

Vascular stents have emerged as an effective treatment for occlusive vascular disease. Despite their success and widespread use, outcomes for patients receiving stents are still hampered by thrombosis and restensosis. As arteries attempt to adapt to the mechanical changes created by stents, they may in fact create a new flow-limiting situation similar to that which they were intended to correct. In vitro fluid mechanics and solid mechanics studies of stented vessels have revealed important information about how stents alter the mechanical environment in the arteries into which they are placed. Adverse nonlaminar flow patterns have been demonstrated as well as remarkably high stress concentrations in the vessel wall. In vivo studies of stented vessels have also shown a strong relationship between stent design and their dynamic performance within arteries. Alterations in pressure and flow pulses distal to the stent have been observed, as well as regional changes in vascular compliance. Considering the influence of flow and stress on the vascular response and the suboptimal clinical outcomes associated with stenting, knowledge gained from stent/artery mechanics studies should play an increasingly important role in improving the long-term patency of these devices. © 2002 Biomedical Engineering Society. PAC2002: 8719Rr, 8780-y, 8719Uv     

The arteries of the humeral head and their relevance in fracture treatment

Bone vascularisation has gained increased interest in relation to the blood supply of bone fragments during treatment of fractures. In the current study the pattern of vascular supply of the proximal humerus was studied in six cadavers by the corrosion technique. Furthermore, the effect of fractures on the vascular supply was also investigated. In all preparations the intraosseous arteries of the humeral head arose from the circumflex arteries, which surrounded the humerus and dispatched branches towards the proximal end. The main vessel was the branch of the anterior circumflex artery, penetrating the major tubercle in six of six cases. Due to the intraosseous arch shape of this vessel it is referred to as the arcuate artery. Besides other smaller vessels, there was also a vascular network arising from the posterior circumflex artery. Their branches penetrated medially at the cartilage bone interface in five of six preparations. The medial bone arteries appear to gain distinctive importance in humeral head fractures by their impact on the vascularisation of the fracture fragments. After disruption of the arterial supply from the arcuate artery, the vascularisation of the head fragments is most likely ensured by this group of vessels. Therefore, necessary repositioning manoeuvres during open reduction of the fracture should be conducted with care in order to preserve these arteries.     

Viscoelastic properties of human arteries methodology and preliminary results

In order to study the biomechanical properties of the arterial wall and to compare arteries with different histologic structures, we designed a device that allows testing of arterial segments under near-physiologic conditions. A hydrodynamic generator simulates systolo-diastolic pressures in an open loop. An intraarterial pressure sensor and a sonomicrometer connected to two piezoelectric crystals placed in diametric opposition on the arterial wall allow computer calculation of compliance, stiffness, midwall radial arterial stress, Young modulus, and incremental modulus for a given arterial segment at a given pressure setting. Seven healthy common carotid artery (CCA) segments and seven healthy (superficial) femoral artery (FA) segments were studied immediately after removal from brain-dead donors between the ages of 18 and 35 years. Histologic examination was performed to determine the density of elastic fibers in the arterial wall. Hysteresis was observed in all segments regardless of pressure settings. Compliance was greater and modulus values and stiffness were lower in CCA than in FA. No evidence of structural change was noted after testing in the circulation loop. These preliminary results open the way to a wide variety of applications for our hydrodynamic circulation loop. Experiments will be undertaken to compare the mechanical properties of arteries before and after cryopreservation.

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Propriétés visco-élastiques des artères humaines. Méthodologie et résultats préliminaires

Résumé Dans le but d'étudier les propriétés mécaniques de la paroi artérielle et de pouvoir établir des comparaisons entre des segments artériels de structure histologique différente, nous avons mis au point un banc d'essai hydrodynamique permettant de tester des segments artériels dans des conditions voisines de la réalité physiologique. Un générateur hydrodynamique permettait d'obtenir dans un circuit ouvert un régime de pressions de type systolo-diastolique. Un capteur de pression intra-artériel, ainsi qu'un sonomicromètre relié à des cristaux piézo-électriques placés de façon diamétralement opposée sur la paroi artérielle, permettaient de calculer, pour un régime de pressions donné et grâce à l'acquisition de données dans un système informatique, la compliance, la rigidité, la contrainte trans-pariétale, le module de Young, le module incrémentiel d'un segment artériel. Nous avons étudié sept artères carotides communes (CC), et sept artères fémorales (superficielles) (F) fraîchement prélevées chez des sujets sains âgés de 18 à 35 ans. Des corrélations avec la richesse en fibres élastiques de la paroi artérielle ont été établies. Nous avons mis en évidence un phénomène d'hystérésis pour chaque artère testée quel que soit le niveau de pression considéré. La compliance des artères CC a été plus importante, les modules et la rigidité ont été moins importants et ce de façon significative par rapport aux artères F. Aucune altération histologique n'a été mise en évidence après passage des segments artériels au banc d'essai. Ces résultas préliminaires nous permettent d'envisager de nombreuses applications à ce travail dont l'une d'entre elles sera la mesure comparative des propriétés mécaniques des artères avant et après cryopréservation.