A non-invasive methodology for ATAA rupture risk estimation.

Ascending thoracic aortic aneurysms (ATAA) are a life-threatening pathology provoking an irreversible dilation with a high associated risk of aortic rupture or dissection and death of the patient. Rupture or dissection of ATAAs remains unpredictable and has been documented to occur at diameters less than 4.5 cm for nearly 60% of patients. Other factors than the aneurysm diameter may highly affect the predisposition to rupture. In order to have a better insight in rupture risk prediction, a bulge inflation bench was developed to test ATAAs samples collected on patients during surgical interventions. Preoperative dynamic CT scans on a cohort of 13 patients were analyzed to estimate volumetric and cross-sectional distensibility. A failure criteria based on in vitro ultimate stretch showed a significant correlation with the aortic membrane stiffness deduced from in vivo distensibility. These results reinforce the significance of stretch-based rupture criteria and their possible non-invasive prediction in clinical practice.

Fluid- and Biomechanical Analysis of Ascending Thoracic Aorta Aneurysm with Concomitant Aortic Insufficiency.

We present a comprehensive and original framework for the biomechanical analysis of patients affected by ascending thoracic aorta aneurysm and aortic insufficiency. Our aim is to obtain crucial indications about the role played by deranged hemodynamics on the ATAAs risk of rupture. Computational fluid dynamics analysis was performed using patient-specific geometries and boundary conditions derived from 4D MRI. Blood flow helicity and wall shear stress descriptors were assessed. A bulge inflation test was carried out in vitro on the 4 ATAAs after surgical repair. The healthy volunteers showed no eccentric blood flow, a mean TAWSS of 1.5 ± 0.3 Pa and mean OSI of 0.325 ± 0.025. In 3 aneurismal patients, jet flow impingement on the aortic wall resulted in large TAWSS values and low OSI which were amplified by the AI degree. However, the tissue strength did not appear to be significantly reduced. The fourth patient, which showed the lowest TAWSS due to the absence of jet flow, had the smallest strength in vitro. Interestingly this patient presented a bovine arch abnormality. Jet flow impingement with high WSS values is frequent in ATAAs and our methodology seems to be appropriate for determining whether it may increase the risk of rupture or not.

Simulation of swallowing dysfunction and mechanical ventilation after a Montgomery T-tube insertion.

The Montgomery T-tube is used as a combined tracheal stent and airway after laryngotracheoplasty, to keep the lumen open and prevent mucosal laceration from scarring. It is valuable in the management of upper and mid-tracheal lesions, while invaluable in long and multisegmental stenting lesions. Numerical simulations based on real-patient-tracheal geometry, experimental tissue characterization, and previous numerical estimation of the physiological swallowing force are performed to estimate the consequences of Montgomery T-tube implantation on swallowing and assisted ventilation: structural analysis of swallowing is performed to evaluate patient swallowing capacity, and computational fluid dynamics simulation is carried out to analyze related mechanical ventilation. With an inserted Montgomery T-tube, vertical displacement (Z-axis) reaches 8.01 mm, whereas in the Y-axis, it reaches 6.63 mm. The maximal principal stress obtained during swallowing was 1.6 MPa surrounding the hole and in the upper contact with the tracheal wall. Fluid flow simulation of the mechanical ventilation revealed positive pressure for both inhalation and exhalation, being higher for inspiration. The muscular deflections, considerable during normal breathing, are nonphysiological, and this aspect results in a constant overload of the tracheal muscle. During swallowing, the trachea ascends producing a nonhomogeneous elongation. This movement can be compromised when prosthesis is inserted, which explains the high incidence of glottis close inefficiency. Fluid simulations showed that nonphysiological pressure is established inside the trachea due to mechanical ventilation. This may lead to an overload of the tracheal muscle, explaining several related problems as muscle thinning or decrease in contractile function.

Estudio biomecánico de las modificaciones del flujo aéreo traqueal durante los movimientos respiratorios y la tos tras la colocación de una endoprótesis. Posible influencia en la retención de secreciones / Biomechanical study of changes in tracheal airflow during respiratory movements and coughing after placement of an endoprosthesis. Possible influence in secretion retention

Es frecuente que sea precisa la utilización de endoprótesis para el tratamiento de las estenosis traqueales. Aunque solucionan el problema de una forma rápida y segura, su colocación acarrea una serie de efectos secundarios. Los más frecuentes, la retención de secreciones. Utilizando un modelo informático que reproduce el comportamiento biomecánico de la tráquea, se pretende dar explicación a los fenómenos que ocurren tras la implantación de una endoprótesis. Se ha estudiado la variación del flujo aéreo producida tras la intervención durante la respiración normal y la tos. Los resultados obtenidos muestran una disminución de las velocidades de circulación del aire, junto con alteraciones en el patrón de flujo, originadas por la propia morfología de la prótesis, que pueden justificar la dificultad que presentan algunos pacientes para eliminar las secreciones respiratorias, permitiendo que estas se acumulen, sobre todo, en los alrededores de la zona de implantación

Frequently, the use of prosthesis is necessary to deal with a tracheal stenosis. They achieve a rapid and safe resolution of the stenosis, but in some instances, their insertion results in some secondary effects, more often, retained secretions. By using a computer-assisted model that mimics the biome chanical behaviour of the trachea, we aimed at clarifying those phenomena occurring following the prosthesis implantation by assessing the airflow changes during both normal breathing and cough. Our results revealed a decrease in airflow speed and changes in flow patterns secondary to the morphological features of the prosthesis, which might be involved in the inability of these patients to clear secretions, which are retained in the periprosthetic area

A pre-operative planning for endoprosthetic human tracheal implantation: a decision support system based on robust design of experiments.

Swallowing depends on physiological variables that have a decisive influence on the swallowing capacity and on the tracheal stress distribution. Prosthetic implantation modifies these values and the overall performance of the trachea. The objective of this work was to develop a decision support system based on experimental, numerical and statistical approaches, with clinical verification, to help the thoracic surgeon in deciding the position and appropriate dimensions of a Dumon prosthesis for a specific patient in an optimal time and with sufficient robustness. A code for mesh adaptation to any tracheal geometry was implemented and used to develop a robust experimental design, based on the Taguchi's method and the analysis of variance. This design was able to establish the main swallowing influencing factors. The equations to fit the stress and the vertical displacement distributions were obtained. The resulting fitted values were compared to those calculated directly by the finite element method (FEM). Finally, a checking and clinical validation of the statistical study were made, by studying two cases of real patients. The vertical displacements and principal stress distribution obtained for the specific tracheal model were in agreement with those calculated by FE simulations with a maximum absolute error of 1.2 mm and 0.17 MPa, respectively. It was concluded that the resulting decision support tool provides a fast, accurate and simple tool for the thoracic surgeon to predict the stress state of the trachea and the reduction in the ability to swallow after implantation. Thus, it will help them in taking decisions during pre-operative planning of tracheal interventions.

Tecnología de simulación tridimensional para la planificación de la implantación de endoprótesis traqueales / Three-dimensional simulation technology for planning tracheal stenting

Objetivo: Se ha realizado un estudio observacional sobre pacientes con estenosis de la vía aérea principal con el objetivo de demostrar la mejorar en los resultados del tratamiento mediante broncoscopia rígida al realizar una planificación preoperatoria (..) (AU)

Objective: An observational study was made of patients with stenosis of the main airway in order to demonstrate the improved results of treatment by rigid bronchoscopy to perform preoperative planning with computer simulation (..) (AU)

[Retinal vasculitis. Epidemiological, clinical and etiological features]. / Les vascularites rétiniennes: profils épidémiologiques, cliniques et étiologiques.

PURPOSE: To study the epidemiological and clinical features of noninfectious retinal vasculitis (NIRV). METHODS: We analyzed 128 consecutive patients with NIRV, collected over 15 years (1993-2007) in an ophthalmological reference university hospital in Tunis, Tunisia. Data were analyzed regarding associated systemic disease, ocular syndromes, anatomic features (type and topography of vessel and type of capillaropathy), age and sex. The results of the etiologic work-up were based on the Levy-Clarke and Perez classification. RESULTS: A total of 240 cases of NIRV (128 patients) were collected (mean age: 32; sex ratio: 2.6). It was bilateral in 93.7% of cases. The mean visual acuity (VA) was 20/50 (range: 20/800-20/20). NIRV was mainly venous (84.1%), diffuse (57%), with a mixed capillaropathy (40.2%). There were complications in 56.25% of the cases, mainly macular edema (48.1%), vascular occlusion (25.9%), optic atrophy (22.2%) and cataract (19.2%). NIRV was idiopathic in 15.6% of the cases, characterized by a predominance of young subjects (mean: 38 years old), males (sex ratio: 4), VA at 20/25, and edematous periphlebitis in 100% of cases. There were ocular disorders in 12.5% of the cases and systemic disease in 72% of the cases, with a predominance of Behçet disease (BD): 53.9% of all patients and 81% of systemic disease with predominant venous features. In 48.3% of cases, VA was less than 20/200, due to BD in 48% of the cases. CONCLUSION: In NIRV, the etiologic work-up is oriented on anatomic presentation, based on fluorescein retinal angiography, and requires an interdisciplinary approach. In young adults with retinal phlebitis, BD is suggested first.

Patient-specific models of human trachea to predict mechanical consequences of endoprosthesis implantation.

Nowadays, interventions associated with the implantation of tracheal prostheses in patients with airway pathologies are very common. This surgery may promote problems such as migration of the prosthesis, development of granulation tissue at the edges of the stent with overgrowth of the tracheal lumen or accumulation of secretions inside the prosthesis. Among the movements that the trachea carries out, swallowing seems to have harmful consequences for the tracheal tissues surrounding the prosthesis. In this work, a finite-element-based tool is presented to construct patient-specific tracheal models, introducing the endotracheal prosthesis and analysing the mechanical consequences of this surgery during swallowing. A complete description of a patient-specific tracheal model is given, and a fully experimental characterization of the tracheal tissues is presented. To construct patient-specific grids, a mesh adaptation algorithm has been developed and the implantation of a tracheal prosthesis is simulated. The ascending deglutition movement of the trachea is recorded using real data from each specific patient from fluoroscopic images before and after implantation. The overall behaviour of the trachea is modified when a prosthesis is introduced. The presented tool has been particularized for two different patients (patient A and patient B), allowing prediction of the consequences of this kind of surgery. In particular, patient A had a decrease of almost 30 per cent in his ability to swallow, and an increase in stresses that were three times higher after prosthesis implantation. In contrast, patient B, who had a shorter trachea and who seemed to undergo more damaging effects, did not have a significant reduction in his ability to swallow and did not present an increase in stress in the tissues. In both cases, there are clinical studies that validate our results: namely, patient A underwent a further intervention whereas the outcome of patient B's surgery was completely successful. Notwithstanding the fact that there are a lot of uncertainties relating to the implantation of endotracheal prostheses, the present work gives a new insight into these procedures, predicting their mechanical consequences. This tool could be used in the future as pre-operative planning software to help thoracic surgeons in deciding the optimal prosthesis as well as its size and positioning.

Experimental characterization and constitutive modeling of the mechanical behavior of the human trachea.

BACKGROUND AND AIMS: Cartilage and smooth muscle constitute the main structural components of the human central airways, their mechanical properties affect the flow in the trachea and contribute to the biological function of the respiratory system. The aim of this work is to find out the mechanical passive response of the principal constituents of the human trachea under static tensile conditions and to propose constitutive models to describe their behavior. METHODS: Histological analyses to characterize the tissues and mechanical tests have been made on three human trachea specimens obtained from autopsies. Uniaxial tensile tests on cartilaginous rings and smooth muscle were performed. Tracheal cartilage was considered an elastic material and its Young's modulus and Poisson's coefficient were determined fitting the experimental curves using a Neo-Hookean model. The smooth muscle was proved to behave as a reinforced hyperelastic material with two families of collagen fibers, and its non-linearity was investigated using the Holzapfel strain-energy density function for two families of fibers to fit the experimental data obtained from longitudinal and transversal cuts. RESULTS: For cartilage, fitting the experimental curves to an elastic model, a Young's modulus of 3.33 MPa and nu=0.49 were obtained. For smooth muscle, several parameters of the Holzapfel function were found out (C(10)=0.877 kPa, k(1)=0.154 kPa, k(2)=34.157, k(3)=0.347 kPa and k(4)=13.889) and demonstrated that the tracheal muscle was stiffer in the longitudinal direction. CONCLUSION: The better understanding of how these tissues mechanically behave is essential for a correct modeling of the human trachea, a better simulation of its response under different loading conditions, and the development of strategies for the design of new endotracheal prostheses.

[Functional outcome after resection followed by a coloanal anastomosis for cancer of the rectum]. / Resultats fonctionnels des resections avec anastomose colo-anale dans les cancers du rectum.

The aim of the study was to asseses the operative, functional results of total proctectomy with coloanal anastomosis (CAA). Between 1990 and 2002, 24 patients (14 males and 10 females ) with a mean age of 50,6 years were operated on for cancer of the rectum and they underwent a total proctectomy with CAA. There was one operative death. 3 patients developed non specific complications. 4 patients experienced a supra anastomosis stenosis and underwent a new straight CAA Functional outcome were evaluated by a scoring system fonction and were considered good in 87 and 84% at 1 and 2 years respectively. Low anterior resection combined with CAA provides good treatment for mid-rectal cancers and for some distal rectal cancers. It had a good functional outcome. However Both procedures and selection of patients who underwent radiotherapy must be carefully performed.

[Neuroendocrine carcinoma in Barrett's esophagus. Report of a case]. / Carcinome neuro-endocrine sur oesophage de Barrett. Rapport d'un cas.

The neuroendocrine tumours of the oesophagus are exceptional. They are a spectrum of heterogeneous tumours often not clearly defined in the literature. We report a case of moderately differentiated neuroendocrine tumour of the oesophagus arising from Barrett's mucosa in 51-year-old man treated surgically and who was free of disease 28 months after excision. We discuss about this case, the classification, the histogenesis and therapeutic approaches of these tumours.

[Colon cancer. Study of 153 cases and comparison with a series of 140 historic cases]. / Le cancer du colon. Etude de 153 cas et comparaison avec une serie historique de 140 cas.

The authors study the epidemiological, diagnostic and therapeutic features of 153 consecutive cases of colon cancers collected between 1985 and 1998. They compare the results with those of a previous study performed in the same hospital service (140 cases between 1966 and 1984). It is a series of 79 men and 74 women (sex ratio = 1.07). The mean age was 56.6 +/- 14 years old with 13.7% of the patients who were less than 40 years old. The operability and the resectability were respectively 98.7% and 83.7% with a global operative mortality of 7.9%. According to the Dukes classification, they were 2 A stages, 73 B stages, 32 C stages and 45 D stages. Starting from 1993, 53% of the C stages an 48% of the B stages had an adjuvant chemotherapy. The comparison between our present results and those of our previous series does not show any modification in what regards the mean age, the cancer frequency in young people, the complicated forms proportion and time needed for the diagnosis by comparison to the beginning of symptomatology. The colic cancer prognostic improvement is attained through an earlier diagnosis, making it possible to reduce the developed forms and the complicated forms proportion, the consequence of which is the operative mortality decrease and the log-range survival increase.