Development of In Vitro Endothelialised Stents - Review.

Endovascular treatment is prevalent as a primary treatment for coronary and peripheral arterial diseases. Although the introduction of drug-eluting stents (DES) dramatically reduced the risk of in-stent restenosis, stent thrombosis persists as an issue. Notwithstanding improvements in newer generation DES, they are yet to address the urgent clinical need to abolish the late stent complications that result from in-stent restenosis and are associated with late thrombus formation. These often lead to acute coronary syndromes with high mortality in coronary artery disease and acute limb ischemia with a high risk of limb amputation in peripheral arterial disease. Recently, a significant amount of research has focused on alternative solutions to improve stent biocompatibility by using tissue engineering. There are two types of tissue engineering endothelialisation methods: in vitro and in vivo. To date, commercially available in vivo endothelialised stents have failed to demonstrate antithrombotic or anti-stenosis efficacy in clinical trials. In contrast, the in vitro endothelialisation methods exhibit the advantage of monitoring cell type and growth prior to implantation, enabling better quality control. The present review discusses tissue-engineered candidate stents constructed by distinct in vitro endothelialisation approaches, with a particular focus on fabrication processes, including cell source selection, stent material composition, stent surface modifications, efficacy and safety evidence from in vitro and in vivo studies, and future directions.

Patient-specific modelling of stent overlap: Lumen gain, tissue damage and in-stent restenosis.

This paper investigates the effects of multiple stents, with and without overlap, on the outcome of stent deployment in a patient-specific coronary artery using the finite element method. Specifically, the objective of this study is to reveal the effect of stent overlap on lumen gain, tissue damage and in-stent restenosis in percutaneous coronary intervention. Based on intravital optical coherency tomography imaging, three-dimensional model of a specific patient's coronary artery was developed, with two constituent layers (media and adventitia) and plaque, using Mimics. Hyperelastic models with damage, verified against experimental results, were used to describe stress-stretch responses of arterial layers and plaque. Abaqus CAE was used to create the models for Resolute Integrity™ drug-eluting stents and tri-folded expansion balloons. The results showed that lumen gain was improved by the overlapping stents than a single stent after deployment; however, damage to the media layer was greater, promoting a higher rate of in-stent restenosis. Meanwhile, the lumen gain achieved with the non-overlapping stents was smaller than that with the overlapping ones, due to an increased recoiling effect. Also, non-overlapping stents induced more tissue damage and higher rate of in-stent restenosis than overlapping stents. With respect to long-term clinical outcomes, the study recommended the use of a single stent where possible or multiple stents with minimal overlaps to treat long or angulated lesions.

Finite element evaluation of artery damage in deployment of polymeric stent with pre- and post-dilation.

Using finite element method, this paper evaluates damage in an arterial wall and plaque caused by percutaneous coronary intervention. Hyperelastic damage models, calibrated with experimental results, are used to describe stress-stretch responses of arterial layers and plaque; these models are capable to simulate softening behaviour of the tissue due to damage. Abaqus CAE is employed to create the finite element models for the artery wall (with media and adventitia layers), a symmetric uniform plaque, a bioresorbable polymeric stent and a tri-folded expansion balloon. The effect of percutaneous coronary intervention on vessel damage is investigated by simulating the processes of vessel pre-dilation, stent deployment and post-stenting dilation. Energy dissipation density is used to assess the extent of damage in the tissue. Softening of the plaque and the artery, due to the pre-dilation-induced damage, can facilitate the subsequent stent deployment process. The plaque and the artery experienced heterogeneous damage behaviour after the stent deployment, caused by non-uniform deformation. The post-stenting dilation was effective to achieve a full expansion of the stent, but caused additional damage to the artery. The continuous and discontinuous damage models yielded similar results in the percutaneous coronary intervention simulations, while the incorporation of plaque rupture affected the simulated outcomes of stent deployment. The computational evaluation of the artery damage can be potentially used to assess the risk of in-stent restenosis after percutaneous coronary intervention.

Optical Tomography of Chemical Elements Synthesized in Type Ia Supernovae.

We report the discovery of optical emission from the nonradiative shocked ejecta of three young type Ia supernova remnants (SNRs): SNR 0519-69.0, SNR 0509-67.5, and N103B. Deep integral field spectroscopic observations reveal broad and spatially resolved [Fe XIV] 5303 Å emission. The width of the broad line reveals, for the first time, the reverse shock speeds. For two of the remnants we can constrain the underlying supernova explosions with evolutionary models. SNR 0519-69.0 is well explained by a standard near-Chandrasekhar mass explosion, whereas for SNR 0509-67.5 our analysis suggests an energetic sub-Chandrasekhar mass explosion. With [S XII], [Fe IX], and [Fe XV] also detected, we can uniquely visualize different layers of the explosion. We refer to this new analysis technique as "supernova remnant tomography".

Delay of transfer from the intensive care unit: a prospective observational analysis on economic effects of delayed in-house transfer.

BACKGROUND: Intensive care unit (ICU) capacity is a scant and precious resource in hospitals. Therefore, an optimal occupancy rate as well as detailed occupation planning is of great importance. Most literature deals with admission to the ICU, while only few discuss discharge from the ICU. Specifically, a delay of transfer from the ICU can cause a shortness of beds, jeopardize urgent patient treatment and lead to a decrease in treatment quality as well as economic downsides. This study examined the incidence, costs and reasons for delayed discharge from the ICU and analyzed the influence of the department the patient was admitted to. METHODS: Over the course of 12 months, the discharges of all 1643 patients of two surgical intensive care units of a large academic medical center were analyzed. Delay in minutes and reasons were recorded and translated into financial figures. A univariate logistic regression model was developed to evaluate the impact of length of stay at the ICU, age, gender, subspecialty and specific ICU on the delay of transfer. In a next step, significant factors of the univariate logistic regression were incorporated into a multivariate regression model. RESULTS: In 326 out of 1312 patients ready for discharge (24.8%), the transfer to the floor was delayed. Time of delay for all patients added up to a total of 265,691 min in 1 year. The application of the internal cost allocation, in which 1 min corresponds to 0.75 Euro cents, led to costs of 199,268 Euros (~ $240,000) for the study period. In 91.7% of the cases, the reason for the delay was the lack of an available or appropriate bed on the regular ward. Multivariate regression analysis revealed that the type of department the patient is admitted to poses a significantly influencing factor for delayed discharge from the ICU. CONCLUSION: Delay in discharge from the ICU is a common problem of economic relevance. The main reason is a lack of appropriate floor beds. Patients from certain specific departments are at a higher risk to be discharged with delay. A solution to this problem lies in the focus on the downstream units. A proper use of the scarce resources is to be pursued because of ethical as well as economic reasons in an increasingly aging population.

Letter to the Editor: Thrombocytopenia After Sutureless Aortic Valve Implantation: Does It Really Matter?

Despite the limited clinical relevance of thrombocytopenia after bioprosthetic aortic valve replacement (AVR), the postoperative depletion of platelet count continues to attract the attention of many authors. The development of thrombocytopenia has been evaluated either in patients receiving a sutureless bioprosthesis (1,2) or in those undergoing transcatheter aortic valve implantation, where cardiopulmonary bypass bears little or no relation to this phenomenon (3). Recently, Sánchez et al. (1) have published their findings on this topic, but their limited experience with the devices used makes their study of doubtful interest. Over three years, 27 patients were implanted with a sutureless bioprosthetic valve and were compared with 50 patients receiving a stented aortic valve. No risk factors that may have predisposed to platelet dysfunction were described in either group.Mortality and number of units of transfused red blood cells also seems to be extremely high for a patient population undergoing elective isolated AVR: it is not clear whether bleeding complications occurred in any patients and re-thoracotomy could not be performed, or whether more liberal transfusion protocols were used. In addition, platelet transfusions in patients from the sutureless group could represent a bias that renders the comparison of postoperative mean platelet volume and platelet distribution width between groups unreliable. It would have been more appropriate to consider postoperative echocardiographic findings because, in case of suboptimal placement of the prosthesis, paravalvular leakage may cause severe hemolysis and thrombocytopenia. At present, clinical data can be derived from other case series (4). At our Center, over a six-year period, AVR was performed using a sutureless, stentless, or stented bioprosthesis in 432, 193, and 180 patients, respectively, with all devices being supplied by the same manufacturer. Perioperative trends in platelet count after sutureless AVR did not show progression towards thrombocytopenia as occurs after stentless AVR (5), but compared favourably with conventional stented AVR (Fig. 1), where platelet depletion has no clinical relevance. Figure 1: Perioperative trends in platelet count after aorticvalve replacement with the sutureless Perceval, stentlessSolo, and stented Crown bioprosthetic valves.References1. Sánchez E, Corrales JA, Fantidis P, Tarhini IS, Khan I, Pineda T, González JR. Thrombocytopenia after aortic valve replacement with Perceval S sutureless bioprosthesis. J Heart Valve Dis 2016;25:75-812. Jiritano F, Cristodoro L, Malta E, Mastroroberto P. Thrombocytopenia after sutureless aortic valve implantation: Comparison between Intuity and Perceval bioprostheses. J Thorac Cardiovasc Surg 2016;152:1631-16333. McCabe JM, Huang PH, Riedl LA, et al. Incidence and implications of idiopathic thrombocytopenia following transcatheter aortic valve replacement with the Edwards Sapien® valves: A single center experience. Catheter Cardiovasc Interv 2014;83:633-6414. Santarpino G, Fischlein T, Pfeiffer S. A word of caution is needed before uttering a word of caution: Thrombocytopenia and sutureless valves. Heart Surg Forum 2016;19:E1695. Pozzoli A, De Maat GE, Hillege HL, Boogaard JJ, Natour E, Mariani MA. Severe thrombocytopenia and its clinical impact after implant of the stentless Freedom Solo bioprosthesis. Ann Thorac Surg 2013;96:1581-1586.

[Aortic valve replacement in the elderly]. / Aortenklappenersatz im Alter.

The treatment of severe symptomatic aortic valve stenosis by conventional aortic valve replacement (AVR) or by transcatheter aortic valve implantation (TAVI) has a good perinterventional prognosis even for patients of advanced age. Having a heart team select the best management strategies based on current guidelines for each individual patient is essential for success. Especially in elderly and increasingly multimorbid patients with sometimes severe preconditions, the detection of functional deficits is relevant not only for the mortality but also for perioperative and postoperative complications as well as the functional outcome. Various methods of geriatric assessment are important supplements to standard risk scores. The aim is to implement targeted interventions to minimize the risk factors and to improve the prognosis for elderly patients. The aim of this article is to provide an overview of the current therapy options for aortic valve replacement and to summarize current aspects of treatment options for elderly patients.

First experience with the new Sorin Crown PRT bioprosthetic aortic valve: early postoperative outcome and hemodynamic performance in 90 patients.

AIM: The Crown PRT (The Phospholipid Reduction Treatment) is a new stent bovine bioprosthesis for aortic valve replacement (AVR). Aim of this paper is to report the postoperative clinical and hemodynamic results after ninety consecutive implants. METHODS: After receiving CE mark in July 2014, two European university centers implanted the new Crown PRT (Sorin Group, Burnaby, Canada) for the first time. Up to now, ninety patients underwent aortic valve replacement, in isolated or combined procedures, for aortic stenosis or insufficiency. Intraoperative transesophageal echocardiogram was used to assess the prosthesis's function. In hospital outcomes and echocardiographic parameters were recorded. RESULTS: Age and Log Euroscore were 71.8±7.9 years and 10.2%±4.5 respectively. In-hospital mortality for isolated AVR was 0%; one patient died after a multiple procedure (overall 30-days mortality 1.1%). No adverse device effects were recorded. Intensive Care Unit stay was 2±5.8 days. At discharge, echocardiogram showed no paravalvular leaks and normal postoperative gradients. CONCLUSION: Our starting results showed that the Crown PRT is safe and reliable, with excellent hemodynamic performance. Further clinical results with a larger population and long term follow-up are needed to assess the versatility and the durability of this new device.

Describing readmissions to an Ebola case management centre (CMC), Sierra Leone, 2014.

Case management centres (CMCs) are part of the outbreak control plan for Ebola virus disease (EVD). A CMC in Sierra Leone had 33% (138/419) of primary admissions discharged as EVD negative (not a case). Fifteen of these were readmitted within 21 days, nine of which were EVD positive. All readmissions had contact with an Ebola case in the community in the previous 21 days indicating that the infection was likely acquired outside the CMC.

Weighted simultaneous algebraic reconstruction technique for tomosynthesis imaging of objects with high-attenuation features.

PURPOSE: This paper introduces a nonlinear weighting scheme into the backprojection operation within the simultaneous algebraic reconstruction technique (SART). It is designed for tomosynthesis imaging of objects with high-attenuation features in order to reduce limited angle artifacts. METHODS: The algorithm estimates which projections potentially produce artifacts in a voxel. The contribution of those projections into the updating term is reduced. In order to identify those projections automatically, a four-dimensional backprojected space representation is used. Weighting coefficients are calculated based on a dissimilarity measure, evaluated in this space. For each combination of an angular view direction and a voxel position an individual weighting coefficient for the updating term is calculated. RESULTS: The feasibility of the proposed approach is shown based on reconstructions of the following real three-dimensional tomosynthesis datasets: a mammography quality phantom, an apple with metal needles, a dried finger bone in water, and a human hand. Datasets have been acquired with a Siemens Mammomat Inspiration tomosynthesis device and reconstructed using SART with and without suggested weighting. Out-of-focus artifacts are described using line profiles and measured using standard deviation (STD) in the plane and below the plane which contains artifact-causing features. Artifacts distribution in axial direction is measured using an artifact spread function (ASF). The volumes reconstructed with the weighting scheme demonstrate the reduction of out-of-focus artifacts, lower STD (meaning reduction of artifacts), and narrower ASF compared to nonweighted SART reconstruction. It is achieved successfully for different kinds of structures: point-like structures such as phantom features, long structures such as metal needles, and fine structures such as trabecular bone structures. CONCLUSIONS: Results indicate the feasibility of the proposed algorithm to reduce typical tomosynthesis artifacts produced by high-attenuation features. The proposed algorithm assigns weighting coefficients automatically and no segmentation or tissue-classification steps are required. The algorithm can be included into various iterative reconstruction algorithms with an additive updating strategy. It can also be extended to computed tomography case with the complete set of angular data.

[CEUS as a tool to uncover an unusual cause of obstructive jaundice]. / KM-verstärkter Ultraschall zur Erkennung der seltenen Ursache eines obstruktiven Ikterus.

Aneurysms within the visceral arteries are rare. Among these, aneurysms of the splenic artery occur most frequently followed by aneurysms of the hepatic arteries. An early diagnosis is easily missed and almost all patients become symptomatic with an acute rupture associated with high mortality. Here we demonstrate the case of a 76-year-old patient who presented with acute upper abdominal pain accompanied by a single episode of vomiting and pyrexia of 39 °C. Laboratory results presented the picture of an obstructive jaundice without evidence for accompanying pancreatitis. Inflammatory markers were within normal limits at onset, but increased dramatically within the next few days. An acute calculous cholecystitis was diagnosed on abdominal ultrasound whereas gastroscopy revealed no relevant changes. Computed tomography was suspicious for pancreatitis of the head with obstruction of the bile duct. Choledocholithiasis was ruled out by ERCP, but symptoms persisted despite papillotomy. Due to raising inflammatory markers and an ongoing impairment of the patients condition, an abdominal CT scan was repeated which revealed the suspicion of a ruptured aneurysm of the common hepatic artery. At the time of transferral we were able to confirm the diagnosis by contrast-enhanced ultrasound and angiography. The patient was immediately forwarded to surgery due to lack of satisfactory endovascular procedures. In summary, the patient suffered from a ruptured spurial aneurysm of the right gastric artery thereby obstructing the common bile duct. Beside CT scans and angiography, this case documents a pivotal role for contrast-enhanced ultrasound in the work-up of visceral artery aneurysms.

Dual-Source computed tomography of the chest in the surgical planning of repeated cardiac surgery.

AIM: When reoperative cardiac surgery is indicated, detailed, three-dimensional imaging of the thorax permits accurate depiction of cardiac anatomy and vascular structures potentially increasing the safety of the surgical procedure. We sought to evaluate the contribution of dual-source multidetector-row computed tomography (DSCT) of the heart and thorax in planning repeated open heart surgery. METHODS: Twenty-eight patients (mean age, 68 years) scheduled for repeated cardiac surgery who had undergone previous coronary artery bypass grafting (n=19) or cardiac valve replacement (8) or combined valvular and bypass surgery (1) underwent contrast-enhanced ECG-gated DSCT (Somatom Definition, Siemens Medical Solutions) of the whole thorax with a temporal resolution of 82 ms and a spatial resolution of 0.4 mm³. The indication for repeated surgery was bypass surgery (N.=6), valve replacement (16), combined bypass and valvular surgery (5) or other reasons (1). Assessment of surgical risk based on DSCT data were performed in terms of the relation of the ascending aorta and cardiac structures to the expected median sternotomy line, graft patency and anatomic course, and the degree of calcification of the ascending aorta and coronary arteries. RESULTS: DSCT findings led to a change of surgical approach for 9/28 (32.1%) patients (non-midline incision, N.=3; surgery performed under circulatory arrest, N.=5; peripheral arterial cannulation before sternotomy, N.=1) and cancellation of surgery for 4/28 (14.3%) patients (heavy aortic and coronary calcifications impeding bypass surgery, N.=2; right heart or aortic aneurysm in close proximity to the sternum in high risk patients, N.=2). The planned surgical approach remained unchanged after DSCT for the remaining15/28 (53.6%) patients. Of 54 bypass graft conduits (20 arterial, 34 venous) visualized on DSCT in 20 patients after previous bypass grafting, 16 arterial and 24 venous grafts were patent, while 4 arterial and 10 venous grafts were occluded. CONCLUSION: DSCT of the heart and thorax is an effective, non-invasive tool for the preoperative planning of repeated cardiac surgery. The technique provides significant information to modify the surgical approach and may increase the safety of the procedure.

Crediting treatments for good outcomes that would have happened anyway: the impact of baseline risk on treatment perceptions.

BACKGROUND: In some patient populations, many would experience good outcomes even if untreated (described as a small baseline risk). It appears that treatments for populations with small baseline risks are perceived as more effective than those for populations with large baseline risks: in essence, treatments are credited for good outcomes that would have happened anyway. Previous research failed to control for differences in treatment effects. OBJECTIVE: To evaluate if the baseline risk of developing an acute condition influences the perceived effectiveness of preventive treatments besides the genuine treatment effect. METHODS: In study 1 (n = 1100) and study 2 (n = 336), general population samples were shown information that systematically differed in size of treatment effect (absolute and relative risk reduction) and the size of the baseline risk of developing a condition. In study 3, medical students (n = 110) were shown treatments that systematically differed in the size of the baseline risk of developing a condition and the type of condition to be prevented (i.e., migraines, heart disease, and pancreatic cancer). Measures included the perceived effectiveness of treatments, intentions to use these treatments, and numeracy. RESULTS: The baseline risk of developing an acute condition influenced the perceived effectiveness of treatments (study 1: F(1,1043) = 66.17, P < 0.001; study 2: F(1,329) = 16.574, P < 0.001; study 3: F(1,98) =14.31, P < 0.001) and, in turn, intention to use the treatment (study 1: F(1,1045) = 7.12, P = 0.008). It caused treatments to be judged as unduly ineffective when the baseline risk was large and vice versa. The influence was independent of treatment effect and was not moderated by numeracy. CONCLUSIONS: Treatments for populations with a small baseline risk of developing the condition are perceived as more effective than those for populations with a large baseline risk.

[Magnetic particle imaging (MPI)]. / Magnetic Particle Imaging (MPI).

Magnetic particle imaging (MPI) displays the spatial distribution and concentration of superparamagnetic iron oxides (SPIOs). It is a quantitative, tomographic imaging method with high temporal and spatial resolution and allows work with high sensitivity yet without ionizing radiation. Thus, it may be a very promising tool for medical imaging. In this review, we describe the physical and technical basics and various concepts for clinical scanners. Furthermore, clinical applications such as cardiovascular imaging, interventional procedures, imaging and therapy of malignancies as well as molecular imaging are presented.

Tibial tubercule osteotomy during medial approach to difficult knee arthroplasties.

INTRODUCTION: Osteotomy of the anterior tibial tubercle (TT) is well known as the approach to difficult knees, in particular those with a low patella, but it has a poor reputation. PATIENTS AND METHODS: This technique was used 21 times in 20 patients (10 males and 10 females) with a mean age of 71 years (range, 42-90 years) for 14 prosthesis revisions (three for septic loosening, 11 for aseptic loosening) and seven knees that had not anteriorly received prior implants (three osteotomies, one synovectomy). The surgical technique included a long (7 cm), thick (>1 cm) fragment retaining its lateral muscle hinge with compression fixation using two screws. In cases with a low patella, the TT was proximally displaced, with amplitude limited by the tibial baseplate. Follow-up was clinical and radiological, lasting a mean 54 months (range, 8-195 months). The clinical results were assessed using the IKS score and the radiological results using the measurement of the patellar index according to the protocol described during the Lyon Knee Days. RESULTS: The mean preoperative IKS scores were: knee, 57.5±22.4; function, 42.6±21.5 (total, 100±33.9); postoperative scores: knee, 84±11.6; function 65±28 (total, 149±32.9). The joint range of motion increased from 73±34.9 to 88±21.1 for a mean gain of 15±23.1. We found a traumatic nondisplaced tibia fracture around a tibial stem, treated conservatively, two stress fractures of the immediate proximal part overhanging the TT with no consequences, one case of stiffness (not related to the osteotomy), and one case of localized skin necrosis on a knee that had undergone several surgeries (secondary scarring). No cases of malunion or migration of the TT were noted. The mean deliberate proximal migration obtained was 13 mm±6 (range, 8-33 mm). The patellar index increased from 0.18±0.20 (range, -0.39 to 0.57) to 0.33±0.19 (range, -0.13 to 0.60). DISCUSSION: This series shows that the indications are rare but invaluable, facilitating the approach and most particularly making it possible to modify the position of the patella, thus contributing to increasing the joint range of motion. Fixation with two screws carries no risk of disassembly if the technique is rigorous. Patellar translation is limited by the tibial tray.

[Three-dimensional reconstruction of central lung tumors based on CT data]. / Dreidimensionale Rekonstruktion von zentralen Lungentumoren basierend auf CT-Daten : Erste klinische Erfahrungen First clinical experiences.

BACKGROUND: CT scanning of the lungs is the standard procedure for preoperative evaluation of central lung tumors. The extent of the tumor and infiltration of central lung structures or lung segments are decisive parameters to clarify whether surgery is possible and the extent of resection. With computer-assisted methods for the segmentation of anatomical structures based on CT data (Fraunhofer MeVis, Bremen) an enhanced, three-dimensional selective visualization is now possible. PATIENTS AND METHODS: From August 2007 through June 2009, 22 patients with central lung tumors were treated at the department of thoracic surgery, University of Schleswig-Holstein, campus Lübeck. There were 15 males and 7 females with a mean age of 60.2 years (range 41-74 years), 18 patients had a long history of smoking, while 4 patients had never smoked. Of the patients 20 had a primary lung carcinoma, 1 patient had local recurrent lung cancer after lobectomy and 1 patient had a central lung metastasis from a non-pulmonary primary carcinoma. A multi-slice detector computer tomogram (MSDCT) scan was performed in all cases. All data were three-dimensionally reconstructed and visualized using special computer-aided software (Fraunhofer MeVis, Bremen). Pulmonary lung function tests, computed postoperative lung volume, bronchoscopic findings, general condition of the patients and the three-dimensionally reconstructed CT data were used for an individual risk analysis and surgical planning. RESULTS: According to the risk analysis 14 out of the 22 patients were surgically treated, 7 patients were staged as functionally inoperable and 1 as technically inoperable. A pneumonectomy was performed in 5 cases, a lobectomy/bilobectomy in 4 cases, an extended lobectomy in 3 cases and 1 case each of a wedge resection and a sleeve resection. Of the 14 patients 2 were classified as stage Ia/b, 7 patients as stage IIa/b and 5 patients as stage IIIa. The median length of time spent in hospital was 8.5±33 days and the mortality rate was 0%. The three-dimensional visualization of the tumor and its anatomical relationship to central pulmonary vessels and the airway system was feasible in all cases. The three-dimensional reconstruction was confirmed in all cases by surgical exploration. CONCLUSION: Three-dimensional reconstruction of CT scan data is a new and promising method for preoperative presentation and risk analysis of central lung tumors. The three-dimensional visualization with anatomical reformatting and color-coded segmentation enables the surgeon to make a more precise strategic approach for central lung tumors.

Optical frequency transfer via 146 km fiber link with 10 -19 relative accuracy.

We demonstrate the long-distance transmission of an ultrastable optical frequency derived directly from a state-of-the-art optical frequency standard. Using an active stabilization system we deliver the frequency via a 146-km-long underground fiber link with a fractional instability of 3 x 10(-15) at 1 s, which is close to the theoretical limit for our transfer experiment. After 30,000 s, the relative uncertainty for the transfer is at the level of 1 x 10(-19). Tests with a very short fiber show that noise in our stabilization system contributes fluctuations that are 2 orders of magnitude lower, namely, 3 x 10(-17) at 1 s, reaching 10(-20) after 4,000 s.

[Femoral neck fractures in patients over 50 years old]. / Les fractures du col du fémur après 50 ans.

INTRODUCTION: Despite many papers and instructional course lectures, therapeutic guidelines are not clearly defined about treatment of femoral neck fractures. The aim of this multicentric French symposium was to prospectively study the results of current therapeutic options in order to propose scientifically proven options. MATERIAL AND METHODS: Three prospective studies were carried out in order to answer to these questions: (1) is it possible with anatomical reduction and stable fixation to lower the non union and osteonecrosis rate? (2) is functional treatment of Garden 1 fractures successful in more than 65 years patients? (3) what criteria are useful to choose the kind of arthroplasty for more than 65 years patients? RESULTS: For the 64 patients between 50 and 65 years old included in the first study, 44 ORIF and 17 prostheses were performed. No open reduction was performed in this series despite a 34% malreduction rate. The risk for displacement after functional treatment of Garden 1 fractures is 31%. For patients over 65 years old, almost fractures are treated in this series by an arthroplasty. The one-year mortality rate after displaced femoral neck fracture was 17%. Functional results were better in total hip prosthesis group than in bipolar or unipolar group. Non cemented stems were not safer than cemented ones in frail patients. DISCUSSION AND CONCLUSIONS: For young patients, ORIF should be the treatment of choice: the initial displacement and its effects on the femoral head vascularisation, the quality of reduction and fixation are the two most significant factors for good outcome. For Garden 1, fractures in patients 65 years old or more, it is proposed to performed an internal fixation despite in two thirds of the cases, it should be unnecessary because non identification of predictive factors of failure. For patients over 65 years old, the type of arthroplasty to perform in displaced fractures is to be chosen according to the preoperative mobility and comorbidities. Because of acetabular erosion with long-term follow-up, it is clearly indicated to perform total hip replacement for patients with life expectancy of 10 years or more. For frail patients, unipolar arthroplasty is the best option. The place for bipolar or uncemented implants is not yet well-defined and more prospective trials are needed. In this multicentric study, results appear quite different in terms of mortality, or functional status. These differences seem to be related to technical choice, geriatric care, nutritional consideration or surgical organisation, all factors that may be of major importance for prognostic.