Reduction of fractures in the minimally invasive (MI) manner can avoid risks associated with open fracture surgery. The MI approach requires specialized tools called percutaneous fragment ...manipulation devices (PFMD) to enable surgeons to safely grasp and manipulate fragments. PFMDs developed for long-bone manipulation are not suitable for intra-articular fractures where small bone fragments are involved. With this study, we offer a solution to potentially move the current fracture management practice closer to the use of a MI approach. We investigate the design and testing of a new PFMD design for manual as well as robot-assisted manipulation of small bone fragments. This new PFMD design is simulated using FEA in three loading scenarios (force/torque: 0 N/2.6 Nm, 75.7 N/3.5 N, 147 N/6.8 Nm) assessing structural properties, breaking points, and maximum bending deformations. The PFMD is tested in a laboratory setting on Sawbones models (0 N/2.6 Nm), and on
swine samples (
= 80 N ± 8 N,
= 150 ± 15 N). A commercial optical tracking system was used for measuring PFMD deformations under external loading and the results were verified with an electromagnetic tracking system. The average error difference between the tracking systems was 0.5 mm, being within their accuracy limits. Final results from reduction maneuvers performed both manually and with the robot assistance are obtained from 7 human cadavers with reduction forces in the range of (
= 80 N ± 8 N,
= 150 ± 15 N, respectively). The results show that structurally, the system performs as predicted by the simulation results. The PFMD did not break during
and cadaveric trials. Simulation, laboratory, and cadaveric tests produced similar results regarding the PFMD bending. Specifically, for forces applied perpendicularly to the axis of the PFMD of 80 N ± 8 N deformations of 2.8, 2.97, and 3.06 mm are measured on the PFMD, while forces of 150 ± 15 N produced deformations of 5.8, 4.44, and 5.19 mm. This study has demonstrated that the proposed PFMD undergoes predictable deformations under typical bone manipulation loads. Testing of the device on human cadavers proved that these deformations do not affect the anatomic reduction quality. The PFMD is, therefore, suitable to reliably achieve and maintain fracture reductions, and to, consequently, allow external fracture fixation.
In this work, the effect of pulsed laser used during the powder bed fusion (L-PBF) additive manufacturing (AM) process on Inconel 718 (IN718) material properties has been investigated. Argon gas ...atomised (AGA) IN718 powder is characterised in terms of flow, density, particle size distribution and morphology. Powder shows mostly spherical morphology with Hausner ratio of 1.17 indicating good flow characteristics. Density optimisation trials are carried out by varying laser power and exposure time. Fabricated samples are characterised in terms of porosity by area fraction analysis using light microscopy and volume fraction analysis using X-ray microcomputed tomography (micro-CT). Minimum porosity of 0.16% is achieved for laser power of 200 W and exposure time of 110 μs Microstructural analysis using the Electron Backscatter Diffraction (EBSD) technique shows limited columnar grain structure in the Z direction and more equiaxed type grains in the XY direction (normal to the Z direction). Tensile test results show 754 MPa yield strength, 1070 MPa ultimate tensile strength and ~24% elongation. Finally, hole drilling residual stress measurements show increase from ~0 MPa to over 450 MPa in tensile stress up to a depth of 1 mm from the top surface of the as-build L-PBF IN718 sample. It has been found that laser pulsing produces higher homogeneity in grain structure and better mechanical properties than that by the continuous laser method.
Additive Manufacturing (AM) is a novel manufacturing method used to produce engineering components in a layer-by-layer fashion. It is currently a very vibrant field of research. A great number of ...different materials and processes have been investigated to manufacture components with novel geometries while realising significant savings in material costs. A specific process called laser powder bed fusion (L-PBF) has been investigated to create parts using metal powders. In this thesis a variation of L-PBF using a power modulated laser source to achieve pulses is investigated. IN718 material was produced using the modulated L-PBF process with two different powder batches and analysed and compared to continuous L-PBF. The material was also subjected to a variety of post-thermal treatments, including heat treatment at 980°C and 1200°C as well as hot isostatic pressing (HIP). All material was characterised in terms of crystal microstructure, static mechanical properties, fracture toughness and hardness. Finally, the as-built condition was characterised in terms of residual stress using the hole drilling and contour methods.
The aim of this work is to determine the impact of post-thermal treatments on the mechanical properties and microstructure of alloy 718 superalloy manufactured through modulated laser powder bed ...fusion. Three post-thermal treatments at 980 °C and 1200 °C with and without hot isostatic pressing are utilised, followed by standard ageing procedure. The tensile mechanical properties, microstructure, crystallography, morphology, fracture impact and hardness after each heat treatment are determined. It has been found that the heat treatment procedure at 980 °C significantly affects the tensile properties while leading to no change in grain size or orientation, and formation of twined grains. A temperature of 1200 °C with and without pressure causes considerable grain growth in comparison with the as-built and 980 conditions and significant formation of twinned grains. Hot isostatic pressing was found to produce the tensile mechanical properties close to those of wrought alloy 718.
In this work, pure Nb processed by Powder Metallurgy Hot Isostatic Pressing (PM HIP) was investigated as a potential alternative to C-103 Nb-based alloy for the manufacture of near-net-shape thruster ...combustion chambers. Three Nb powders with varied particle size range (fine, mid-range and coarse) and C-103 powder were investigated to understand the differences in particle size distribution (PSD), morphology and oxygen (O) content present in the alloy chemistry. The as-HIPed microstructures of pure Nb and C-103 are characterised by a near to fully dense microstructure and the absence of PPBs. Microstructural analyses performed on pure Nb highlighted the influence of particle size on the average as-HIPed grain size. Additionally, it was observed that O content plays a crucial role in the microhardness of pure Nb. Tensile tests performed on Nb mid-range and on Nb mid-range sieved showed that a simple sieve operation was effective in increasing the strength of the material while maintaining good levels of elongation. Alternatively, it was also demonstrated that pure Nb powder heat treatment can be regarded as an effective way to increase the O levels in pure Nb powders as witnessed by the high hardness levels. On the other hand, as-HIPed C-103 powder showed superior tensile properties if compared to the minimum specifications for wrought C-103. Finally, to summarise, the work performed on pure Nb, a simple structure-property relation model was developed to predict the YS of pure Nb based on the O levels and grain size of the as-HIPed microstructure.
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•PM HIP was successfully used to consolidate pure Nb and C-103 with absence of PPBs.•Powder characteristics play a crucial role in the as-HIP properties of pure Nb.•Oxygen levels strongly affect the mechanical properties of as-HIPed Nb.•HIPed C-103 showed superior tensile properties if compared to wrought C-103.
Transoesophageal echocardiography (TOE) is a well-established imaging modality, providing more accurate and of higher quality information than transthoracic echocardiography (TTE) for a wide spectrum ...cardiac and extra-cardiac diseases. The present paper represents an effort by the Echocardiography Working Group (WG) of the Hellenic Cardiology Society to state the essential steps of the typical TOE exam performed in echo lab. This is an educational text, describing the minimal requirements and the preparation of a meticulous TOE examination. Most importantly, it gives practical instructions to obtain and optimize TOE views and analyses the implementation of a combined two-and multi-dimensional protocol for the imaging of the most common cardiac structures during a TOE. In the second part of the article a comprehensive review of the contemporary use of TOE in a wide spectrum of valvular and non-valvular cardiac diseases is provided, based on the current guidelines and the experience of the WG members.
Transoesophageal echocardiography (TOE) is a well-established and valid imaging modality, providing more accurate and of higher quality information than transthoracic echocardiography (TTE) for ...several specific diagnoses and recently a useful guide of an increasing number of catheter-based and surgical interventions. The present paper represents an effort by the Echocardiography Working Group (WG) of the Hellenic Society of Cardiology to state the essential steps of the TOE exam performed beyond the echo lab: a) in the operating rooms intraoperatively during either transcatheter interventions, or cardiothoracic surgery and b) in the intensive care unit for critically ill patients' monitoring. This paper includes information and tips and tricks about the pre-procedural evaluation, the procedural echocardiographic guidance and post - procedural evaluation of the result and potential complications.Transoesophageal echocardiography (TOE) is a well-established and valid imaging modality, providing more accurate and of higher quality information than transthoracic echocardiography (TTE) for several specific diagnoses and recently a useful guide of an increasing number of catheter-based and surgical interventions. The present paper represents an effort by the Echocardiography Working Group (WG) of the Hellenic Society of Cardiology to state the essential steps of the TOE exam performed beyond the echo lab: a) in the operating rooms intraoperatively during either transcatheter interventions, or cardiothoracic surgery and b) in the intensive care unit for critically ill patients' monitoring. This paper includes information and tips and tricks about the pre-procedural evaluation, the procedural echocardiographic guidance and post - procedural evaluation of the result and potential complications.
Stress echocardiography (SE) is a well established and valid technique, widely used for the diagnostic evaluation of patients with ischemic and nonischemic cardiac diseases. This statement of the ...Echocardiography Working Group of the Hellenic Society of Cardiology summarizes the consensus of the writing group regarding the applications of SE, based on the expertise of their members and on a critical review of present medical literature. The main objectives of the consensus document include a comprehensive review of SE methodology and training—which focus on the preparation, the protocols used, the analysis of the SE images, and updated, evidence-based knowledge about SE applications on ischemic and nonischemic heart diseases, such as in cardiomyopathies, heart failure, and valvular heart disease.
AS, aortic stenosis; MR, mitral regurgitation; MS, mitral stenosis; AR, aortic regurgitation; HFpEF, Heart Failure with preserved Ejection Fraction; HOCM, Hypertrophic obstructive cardiomyopathy; DCM, dilated cardiomyopathy. Display omitted
Soluble ST2, a member of the of the Toll/IL-1 superfamily, is a novel biomarker with exceptional predictive value in heart failure and myocardial infarction- related mortality as well as in acute ...dyspneic states. Soluble ST2 is considered a decoy receptor of IL 33 that blocks the protective effects of the cytokine in atherosclerosis and cardiac remodeling. In the present study we investigated the differences in the levels of soluble ST2, BNP and hs-CRP between healthy controls and patients with type 2 diabetes with and without left ventricular diastolic dysfunction. A secondary aim was to investigate correlations between sST2 and other biomarkers of type 2 diabetes, such as HbA1c.
158 volunteers were recruited and underwent a complete Doppler-echocardiographic evaluation of both systolic & diastolic cardiac function. All subjects with ejection fraction<50% were excluded. The study population was divided in 4 groups as follows: A: 42 healthy controls, B: 18 subjects without diabetes with LVDD, C: 48 patients with type 2 diabetes without LVDD & D: 50 patients with type 2 diabetes & LVDD. ELISA technique was performed to measure sST2 levels. Statistical analysis was performed with Kruskal-Wallis & Mann-Whitney test (continuous variables), chi squared & Fischer exact test (discrete variables), Spearman coefficient (univariate analysis) and step-wise backward method (multivariate analysis).
Patients with type 2 diabetes with (p<0.001) or without LVDD (p=0.007) had higher serum ST2 levels compared to healthy controls, state found also for hs-CRP levels but not for the corresponding BNP levels (p=0.213 & p=0.207 respectively). Patients with type 2 diabetes & LVDD had higher serum ST2 in relation to diabetic patients without LVDD (p=0.001). In multivariate analysis HbA1c positively and independently correlated with sST2 levels in both groups of patients with type 2 diabetes.
Patients with type 2 diabetes exhibit higher sST2 levels compared to healthy controls. The presence of LVDD in patients with type 2 diabetes is associated with even higher sST2 levels. A significant correlation between glycemic control and sST2 levels was also revealed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Background Because clopidogrel is converted to its active metabolite by P450 isoenzymes, which are also involved in the metabolism of omeprazole, there is concern regarding whether the action of ...clopidogrel would be reduced in patients also taking omeprazole. Objective To evaluate the impact of omeprazole administration on the effectiveness of clopidogrel drug therapy during the first year following successful coronary stenting (CS). Methods A total of 588 consecutive patients who underwent successful CS for stable or unstable coronary artery disease were studied. Patients were classified into those who were treated (group A, n = 340) or not treated (group B, n = 248) with omeprazole for seven or more consecutive days during the entire observation period. The composite of cardiac death or rehospitalization for nonfatal myocardial infarction during the first year was the prespecified primary study end point. Results Baseline characteristics, and dual clopidogrel and acetylsalicylic acid drug therapy were well balanced between the study groups. By one year, the primary end point was reached by 58 (9.9%) patients, including 20 (3.4%) who died due to cardiac reasons and 38 (6.5%) who were rehospitalized because of a nonfatal myocardial infarction. Patients in groups A and B, respectively, were at similar risk of the primary composite end point (10% versus 9.7%, hazard ratio 1.1 95% CI 0.6 to 1.8; P = 0.89). Conclusions According to the results of the present study, treatment with omeprazole had no impact on the clinical efficacy of clopidogrel drug therapy during the first year after successful CS.
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