Three-dimensional modeling and numerical predictions of multimodal nonlinear behavior in damaged concrete blocks.

In this paper, the multimodal nonlinear elastic behavior of concrete, which is representative of a consolidated granular material, is modeled numerically. Starting from a local three-dimensional softening law, the initial stiffness properties are re-estimated according to the local strain field. The experiments deal with samples of thermally damaged concrete blocks successively excited around their first three modes of vibration. The geometry of these samples cannot be described by a one-dimensional approximation in these experiments where compressional and shear motions are strongly coupled. Despite this added complexity, the nonlinear behavior for the three modes of vibration of the samples is well captured by the simulations using a single scalar nonlinear parameter appropriately integrated into the elasticity equations. It is shown that without sufficient attention paid to the latter, the conclusions would have brought erroneous statements such as nonlinearity dispersion or strain type dependence.

Quantitative linear and nonlinear resonance inspection techniques and analysis for material characterization: application to concrete thermal damage.

Developed in the late 1980s, Nonlinear Resonant Ultrasound Spectroscopy (NRUS) has been widely employed in the field of material characterization. Most of the studies assume the measured amplitude to be proportional to the strain amplitude which drives nonlinear phenomena. In 1D resonant bar experiments, the configuration for which NRUS was initially developed, this assumption holds. However, it is not true for samples of general shape which exhibit several resonance mode shapes. This paper proposes a methodology based on linear resonant ultrasound spectroscopy, numerical simulations and nonlinear resonant ultrasound spectroscopy to provide quantitative values of nonlinear elastic moduli taking into account the 3D nature of the samples. In the context of license renewal in the field of nuclear energy, this study aims at providing some quantitative information related to the degree of micro-cracking of concrete and cement based materials in the presence of thermal damage. The resonance based method is validated as regard with concrete microstructure evolution during thermal exposure.

Probing the interior of a solid volume with time reversal and nonlinear elastic wave spectroscopy.

A nonlinear scatterer is simulated in the body of a sample and demonstrates a technique to locate and define the elastic nature of the scatterer. Using the principle of time reversal, elastic wave energy is focused at the interface between blocks of optical grade glass and aluminum. Focusing of energy at the interface creates nonlinear wave scattering that can be detected on the sample perimeter with time-reversal mirror elements. The nonlinearly generated scattered signal is bandpass filtered about the nonlinearly generated components, time reversed and broadcast from the same mirror elements, and the signal is focused at the scattering location on the interface.

Quantification of material nonlinearity in relation to microdamage density using nonlinear reverberation spectroscopy: Experimental and theoretical study.

High amplitude vibrations induce amplitude dependence of the characteristic resonance parameters (i.e., resonance frequency and damping factor) in materials with microscopic damage features as a result of the nonlinear constitutive relation at the damage location. This paper displays and quantifies results of the nonlinear resonance technique, both in time (signal reverberation) and in frequency (sweep) domains, as a function of sample crack density. The reverberation spectroscopy technique is applied to carbon fiber reinforced plastic (CFRP) composites exposed to increasing thermal loading. Considerable gain in sensitivity and consistent interpretation of the results for nonlinear signatures in comparison with the linear characteristics are obtained. The amount of induced damage is quantified by analyzing light optical microscopy images of several cross-sections of the CFRP samples using histogram equalization and grayscale thresholding. The obtained measure of crack density is compared to the global macroscopic nonlinearity of the sample and explicitly confirms that the increase in nonlinearity is linked to an increased network of cracks. A change from 1% to 3% in crack density corresponds to a tenfold increase in the signature of nonlinearity. Numerical simulations based on a uniform distribution of a hysteretic nonlinear constitutive relation within the sample support the results.

Aortoiliac reconstruction and kidney transplantation: a multicenter study.

The occurrence of aortoiliac lesions with renal transplantation is an increasingly common combination that causes problems regarding operative strategy and indications for aortoiliac reconstruction and renal transplantation. To gain greater insight into these problems we undertook a retrospective multicenter study based on data from 24 kidney transplantation centers in France. A total of 83 patients who underwent both aortoiliac reconstruction and kidney transplantation were enrolled. Patients were divided into two groups according to the order in which the two procedures were performed. Group I included 36 patients in whom aortoiliac reconstruction was performed before kidney transplantation-either during the same procedure (6 patients) or as separate procedures (30 patients). Group II included 47 patients in whom aortoiliac reconstruction was performed after kidney transplantation. The mean age was 49.9 years. There were 43 abdominal aortic aneurysms (51.8%), 36 occlusive aortoiliac lesions (43.4%), and 4 aortoiliac dissections (4.8%). Prosthetic bypass grafting was performed in 72 cases (86.8%), transluminal angioplasty in 6 cases (7.2%), endarterectomy in 3 cases (3.6%), and arterial autograft bypass in 1 case. Renal transplant protection was used during aortoiliac clamping in only 3 patients in group II (7.3%). One month after the second procedure (i.e., kidney transplantation in group I and aortoiliac reconstruction in group II), creatinemia was <200 micromol/L in 27 patients (87.1%) in group I and in 37 patients (88.1%) in group II. The graft survival rate was 86.1% in group I and 89.3% in group II. The overall postoperative morbidity rate was 36.1% (13 cases) in group I and 36.1% (17 cases) in group II. One year after the second procedure creatinemia was <200 micromol/L in 29 patients (93.5%) in group I and 36 patients (93%) in group II. The graft survival rate was 86.1% in group I and 85.1% in group II. The outcome of kidney transplantation is comparable regardless of whether the procedure is performed alone or in association with aortoiliac reconstruction. This finding indicates that kidney transplantation should be performed in patients presenting indications for prior aortoiliac reconstruction. The outcome of aortoiliac reconstruction without graft protection in kidney transplant patients is comparable to the outcome of conventional aortoiliac reconstruction in patients with native kidneys.

Revascularization of internal iliac arteries during aortoiliac surgery: a multicenter study.

In 1995, a total of 1785 patients underwent elective aortoiliac surgery at 35 centers in France, including 1024 for abdominal aortic aneurysm (57.4%) and 761 for occlusive aortoiliac lesions (42.6%). Direct revascularization of the internal iliac artery was performed in 11.2% of patients with both distal anastomoses located below the iliac bifurcations (18.4% with aneurysm vs. 6.8% with occlusive lesions, p < 0.001). Associated revascularization of the inferior mesenteric artery was performed in 9% of patients (11.5% with aneurysms vs. 5.5% with occlusive lesions, p < 0.001). Postoperative colonic ischemia was observed in 21 patients (1.2%) (1.2% with aneurysms vs. 1.2% with occlusive lesions) and claudication in the gluteal region was observed in 31 patients (1.7%) (1.5% with aneurysms vs. 2.1% with occlusive lesions). Revascularization of the internal iliac artery, regardless of the technique, had no significant effect on the incidence of postoperative colonic ischemia and claudication in the gluteal region-neither after surgery for aneurysm (0.6% vs. 2.1% and 1.2% vs. 1.9%, respectively) nor after surgery for occlusive lesions (0.9% vs. 0.4% and 1.5% vs. 2.6%, respectively). Whether performed routinely or not, revascularization of the mesenteric artery has no significant effect on the incidence of postoperative colonic ischemia (1.1% vs. 1.3%).

Role of direct revascularization of the internal iliac artery during aortoiliac surgery.

The purpose of this retrospective study was to determine the indications and efficacy of direct revascularization of the internal iliac arteries during aortoiliac reconstruction in the prevention of postoperative colonic and pelvic ischemia. This study included 540 patients who underwent aortoiliac reconstruction between January 1987 and December 1996 for nonruptured abdominal aortic aneurysm in 341 cases (63%) and occlusive aortoiliac disease in 199 cases (37%). Mean age was 67.4 years. A tubular aortic prosthetic graft was used in 36 patients and a bifurcated prosthetic graft in the remaining 504 patients. Direct revascularization of the internal iliac artery was performed 102 times in 85 patients (72 with aortic aneurysms and 13 with occlusive aortoiliac disease). The indication for direct revascularization was absence of adequate retrograde flow in 54 cases (53%), absence of anterograde flow in 19 cases (19%), and aneurysmal involvement of the origin of one internal iliac artery in 29 cases (28%). Concomitant revascularization of the inferior mesenteric artery was performed in 14 cases (2.5%). Twenty-two patients (4.1%) died during the immediate postoperative period and two (0.4%) presented nonfatal colonic ischemia. Fatal pelvic ischemia occurred in one patient following treatment of an aortoiliac aneurysm with retrograde revascularization of the internal iliac artery. Postoperative rest pain due to buttock ischemia was observed in three patients (0.6%) in whom direct revascularization of the internal iliac artery was not performed. In the subgroup of patients who underwent direct revascularization of the internal iliac artery, there were 3 deaths (3.5%), 13 nonfatal complications (15.3%), and no colonic ischemia. In this series direct revascularization of the internal iliac artery was performed in a high proportion of cases (15.7%) and did not increase the postoperative morbidity/mortality rate. The incidence of postoperative colonic and pelvic ischemia was low (0.6%). Direct revascularization of the internal iliac artery in selected patients appears to be effective in the prevention of postoperative pelvic and colonic ischemia.

Lower limb trauma caused by power-driven cultivators: report of 23 cases.

OBJECTIVE: To determine the mechanism and the severity of injuries caused by power-driven cultivators. METHODS: This retrospective study analyzed the clinical records of 20 patients treated from 1984 to 1996 for a total of 23 lower limb injuries caused by power-driven cultivators (three patients had bilateral injuries) in the Nice University Hospital. RESULTS: A total of 90% of the accidents occurred when the machine was put into reverse and the limb was caught by the rotary blades; the cause of the remaining accidents was unknown. Of the 23 patients, 10 patients (43.5%) suffered posterior dislocation of the knee due to forced hyperextension. Injuries were classed in two groups as a function of their prognosis: group I consisted of osteomuscular lesions without vascular or nerve involvement (11 lower limbs, 11 patients). The mortality rate in this group was 9%, the rate of major amputation was 18%, and the prognosis was favorable in 82% of the cases. Group II corresponded to lower limb injuries with neurovascular involvement (12 lower limb injuries in 10 patients: one patient belonged to both group I and group II). Acute lower limb ischemia was constant in group II; the mortality rate was 20% (two of 10 patients), and the rate of major amputation was 41.6% (five of 12 patients; three emergency amputations and two secondary amputations). CONCLUSION: These agricultural machines can cause severe trauma, and the resulting wounds are contaminated by telluric germs in rural areas. Paradoxically, power-driven cultivators are not legally classified as "dangerous machines." Modification of existing legislation in this field would seem advisable.

Abdominal aortic aneurysm and lower-limb occlusive arterial disease.

BACKGROUND: Abdominal aortic aneurysms (AAA) are associated with lower-limb occlusive arterial disease (LLOAD) in 20-40% of patients. Retrospective analysis of 200 elective AAA repairs and comparison with literature data revealed that LLOAD has little influence on standard therapeutic management of AAA. METHODS: In this study, only 2.5% of the patients required femoropopliteal bypass along with aneurysm repair. In contrast, aneurysm repair was associated with lumbar sympathectomy in 30% of cases owing to existence of peripheral arterial disease. RESULTS: Concurrent LLOAD did not significantly increase the operative mortality of AAA, but postoperative peripheral arterial complications were more frequent in patients with both aneurysmal and occlusive disease. CONCLUSIONS: Although concomitant LLOAD did not adversely affect the long-term survival of patients who underwent surgical repair of AAA, this subgroup of patients was at higher risk of aggravation of their lower extremity arterial lesions.

Proximal arterial dilatation developing after surgical closure of long-standing posttraumatic arteriovenous fistula.

Concomitant discovery of long-standing arteriovenous fistula (AVF) and proximal dilatation is commonplace whereas the disclosure of proximal arterial dilatation several years after closure of AVF is much more surprising and less often described. The goal of this study was to call attention to this late complication, to evaluate its prevalence, and to describe the mechanism and outcome after treatment. Six new observations were added to 11 cases already published in the literature. Most AVF were located in the popliteal or superficial femoral arteries. The mean duration of these AVF was 20 years and 7 months. The mean delay between closure of AVF and the discovery of arterial dilatation was 9 years and 8 months. One patient required emergency operation for rupture. Another patient sustained embolism. All patients were treated by exclusion-bypass. Six years after operation for arterial dilatation, one patient had to be reoperated on for impending rupture of an aortic aneurysm. These facts lead us to advocate 1) closure of all AVF, even when iatrogenic, whenever present for 45 days or longer, 2) careful observation of all patients after operation for long-standing AVF, 3) operation on all patients with arterial dilatation secondary to AVF, and 4) life-long surveillance of the proximal arteries of these patients.

Visceral artery aneurysms in Von Recklinghausen's neurofibromatosis.

We report the case of a patient with Von Recklinghausen's neurofibromatosis in whom two visceral artery aneurysms were diagnosed: a 4 cm aneurysm originating from the common hepatic artery and a smaller aneurysm originating from the superior mesenteric artery. The hepatic artery aneurysm underwent successful embolization. Because of the patient's poor general condition, the superior mesenteric aneurysm was considered inoperable and has been kept under surveillance by ultrasonography. Arterial involvement in Von Recklinghausen's neurofibromatosis is a well-known but infrequent occurrence. Stenotic lesions predominate, with the renal arteries being the site of predilection. Aneurysmal defects are less common, and involvement of the visceral arteries is exceptional. Only three reports of superior mesenteric artery aneurysm in patients with Von Recklinghausen's neurofibromatosis were found in the literature, and hepatic artery aneurysm has never previously been described in this disease.

Buttock claudication from isolated stenosis of the gluteal artery.

Buttock claudication is usually caused by proximal arterial obstruction in the aorta or the common iliac artery. We report an unusual case of buttock claudication caused by isolated stenosis of the superior gluteal artery diagnosed by angiography. Both physical examination and noninvasive vascular explorations had been unremarkable. Twenty-six months after undergoing treatment by percutaneous transluminal angioplasty, the patient has no symptoms. Buttock claudication related to unilateral stenosis of the superior gluteal artery as observed in this case can be successfully managed by percutaneous transluminal angioplasty.

Secondary rupture of an iliac artery aneurysm after exclusion-bypass.

We report a case of secondary rupture of a common iliac artery aneurysm into the common iliac vein. Exclusion of the iliac aneurysm had been performed 2 years earlier in association with reconstruction of an aortic aneurysm that had ruptured into the interior vena cava. After closure of the aortocaval fistula by the endoaneurysmal route, aortobifemoral bypass grafting had been performed and a caval clip had been placed. The common iliac arteries had been sutured by the endoaneurysmal route and the right common iliac artery had been excluded by ligation of the right iliac artery. Occlusion of the interior vena cava distal to the caval clip resulted in increased peripheral venous hypertension causing the secondary arteriovenous fistula (rupture of scrotal varices and edema of lower extremities) but prevented right cardiac insufficiency. This observation confirms the possibility of secondary rupture after treatment of an aneurysm by exclusion. Thus the inclusion-graft technique is more reliable.

[Treatment of abdominal aortic aneurysms: importance of the bifurcated prosthesis]. / Traitement des anévrismes de l'aorte abdominale: intérêt des prothèses bifurquées.

Despite the increasing use of tube grafts to treat aortic aneurysms, bifurcated prostheses remain the most frequent solution. Advocates of the tube graft emphasize faster positioning and lower operative morbidity and mortality rates. However, the condition of the aortic orifice (where atheromatous lesions are maximal) and the aneurysmal or occlusive iliac disease frequently associated with aortic aneurysms usually require use of a bifurcation prosthesis for complete treatment of aortoiliac lesions.

[[Aneurysm of the abdominal aorta and arteritis of the legs]. / Anévrisme de l'aorte abdominale et artérite des membres inférieurs.

Twenty to forty percent of patients with aneurysms of the abdominal aorta also have obliterated arteries of the lower limbs. We analyzed retrospectively a series of 200 patients undergoing elective surgery for aneurysm of the abdominal aorta and compared the results with data in the literature. Obliteration of the lower limb arteries had little influence on the technique usually employed for surgery. Femoro-popliteal bypass was associated with cure of the aneurysm in only 2.5% of the cases. We also performed sympathectomy of the lumbar branches in 30% of the cases because of peripheral arterial lesions. The presence of obliterations did not significantly increase operative mortality. Inversely, post-operative peripheral arterial complications were more frequent in patients with an obliterated artery of the lower limb than in those free of distal disease. Long-term survival was not unfavourably affected by the presence of obliterated arteries, but such patients have a greater risk of arterial lesions of the lower limbs.

Subadventitial rupture of the splanchnic arteries as the result of blunt abdominal trauma presenting with acute gastric dilatation.

Two patients are reported who presented with intestinal ischaemia caused by a subadventitial rupture of the origin of the coeliac trunk and superior and inferior mesenteric arteries after blunt trauma from deceleration injury. In both cases the initial clinical examination revealed a painful abdomen without any 'peritonism'. Abdominal ultrasonographic examination showed no abnormality. Plain abdominal radiography showed gastric dilatation in both patients. In the first, the diagnosis was made by laparatomy but only after 2 days. In the second, diagnosis was made by aortography performed because of the early appearance of gastric dilatation. Both patients died as a result of extensive associated injuries and delay in diagnosis.

[Thrombophlebitis of the ovarian vein with a floating clot in the inferior vena cava]. / Thrombophlébite de la veine ovarienne avec caillot flottant dans la veine cave inférieure.

The authors report two recent observations of thrombophlebitis of the right ovarian vein. The first occurred after a cesarotomy, due to a bigeminal pregnancy, and the second, after a breech delivery. The diagnosis was given when faced to a febrile syndrome and pains of the right flank and confirmed in both cases by an abdominal tomodensimetric examination. In both cases, an enlargement of the lower vena cava thrombosis was observed with a floating clot that reached the renal veins. Both patients underwent a surgery. The latter consisted in both cases in a thrombectomy of the lower vena cava as well as a ligature of the right ovarian vein. In both cases, the evolution was positive, thanks to a remote-control of the lower vena cava via tomodensimetry. This therapeutic procedure and other potential therapies were discussed.

[Atheromatous pseudo-occlusive stenosis of the internal carotid]. / Les sténoses athéromateuses pseudo-occlusives de la carotide interne.

Pseudo-occlusion of the internal carotid artery is defined as an angiographically occluded but anatomically patent artery. Between january 1980 and december 1990, 14 cases were diagnosed in our institution. Preoperative Doppler examination of the internal carotid artery suggested almost complete thrombosis in 11 patients and occlusion in 3. The angiographic appearance suggested internal carotid occlusion in all but the presence of the slim sign was in favor of a patent artery. All 14 patients underwent surgery. There were no postoperative deaths; one patient presented an ipsilateral TIA post operatively; 3 others presented an ipsilateral TIA after 2, 16 and 30 months respectively. All carotid arteries were found to be patent. The frequency of pseudo-occlusion of the internal carotid artery is probably underestimated. It must be kept in mind whenever an apparently occluded internal carotid continues to be symptomatic. Diagnosis is based on comparative analysis of Doppler examination and angiographic findings. Surgery is indicated whenever doubt persists.

Persistent hypoglossal artery.

During embryological development, the hypoglossal artery serves as a transient anastomosis between the internal carotid artery and the vertebro-basilar system. This artery occasionally persists into adult life. Two cases of persistent hypoglossal artery we have recently encountered are reported here. The embryology, diagnosis and potential problems for carotid surgery are discussed.

Hydronephrosis after aortofemoral bypass graft. A prospective study.

This prospective study was designed to determine the frequency and natural history of hydroureteronephrosis (HUN) after placement of an aortobifemoral vascular graft. A total of 30 patients were evaluated by the study protocol, which included: pre and postoperative biological kidney function tests, preoperative and early postoperative (14th day) intravenous pyelograms and a late (mean 18th month) urologic examination by renal ultrasonic tomography. Four asymptomatic, early cases of HUN were observed in the 57 ureters examined (7%); all four complications regressed in less than 30 days. No cases of symptomatic early or late HUN were observed in this series. Asymptomatic early HUN was a frequent complication in our series (7%) but its benign course does not justify systematic screening. These asymptomatic complications contrast with the symptomatic cases of early or late HUN reported in the literature which necessitated urologic and vascular investigations.