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Medical Engineering & Physics

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https://www.readbyqxmd.com/read/29042144/a-comparative-surface-topographical-analysis-of-explanted-total-knee-replacement-prostheses-oxidised-zirconium-vs-cobalt-chromium-femoral-components
#1
Emma Kennard, Susan C Scholes, Raghavendra Sidaginamale, Rajkumar Gangadharan, David J Weir, James Holland, David Deehan, Thomas J Joyce
It has been proposed that an increased surface roughness of the femoral components of Total Knee Replacements (TKRs) may be a contributing factor to the accelerated wear of the polyethylene (PE) bearing and ultimately prosthesis failure. Oxidised Zirconium was introduced to the orthopaedic market in an attempt to reduce PE wear associated failures and increase the longevity of the prosthesis. In this study, non-contacting profilometry was used to measure the surface roughness of the femoral components of 6 retrieved TKRs (3 Oxidised Zirconium (OxZr) and 3 Cobalt Chromium alloy (CoCr) femoral components) and 2 as-manufactured femoral components (1 OxZr and 1 CoCr)...
October 14, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28935262/identification-of-the-period-of-stability-in-a-balance-test-after-stepping-up-using-a-simplified-cumulative-sum
#2
Doha Safieddine, Aly Chkeir, Cyrille Herlem, Delphine Bera, Michèle Collart, Jean-Luc Novella, Moustapha Dramé, David J Hewson, Jacques Duchêne
Falls are a major cause of death in older people. One method used to predict falls is analysis of Centre of Pressure (CoP) displacement, which provides a measure of balance quality. The Balance Quality Tester (BQT) is a device based on a commercial bathroom scale that calculates instantaneous values of vertical ground reaction force (Fz) as well as the CoP in both anteroposterior (AP) and mediolateral (ML) directions. The entire testing process needs to take no longer than 12 s to ensure subject compliance, making it vital that calculations related to balance are only calculated for the period when the subject is static...
September 18, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28927643/a-combined-kinematic-and-kinetic-analysis-at-the-residuum-socket-interface-of-a-knee-disarticulation-amputee
#3
Jinghua Tang, Michael McGrath, Nick Hale, Liudi Jiang, Dan Bader, Piotr Laszczak, David Moser, Saeed Zahedi
The bespoke interface between a lower limb residuum and a prosthetic socket is critical for an amputee's comfort and overall rehabilitation outcomes. Analysis of interface kinematics and kinetics is important to gain full understanding of the interface biomechanics, which could aid clinical socket fit, rehabilitation and amputee care. This pilot study aims to investigate the dynamic correlation between kinematic movement and kinetic stresses at the interface during walking tests on different terrains. One male, knee disarticulation amputee participated in the study...
September 15, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28927642/iterative-approach-for-3d-reconstruction-of-the-femur-from-un-calibrated-2d-radiographic-images
#4
Kibeom Youn, Moon Seok Park, Jehee Lee
Three-dimensional reconstruction of the femur is important for surgical planning in patients with cerebral palsy. This study aimed to reconstruct the three-dimensional femur shape from un-calibrated bi-planar radiographic images using self-calibration to allow for low-dose preoperative planning. The existing self-calibration techniques require anatomical landmarks that are clearly visible on bi-planar images, which are not available on the femur. In our newly developed method, the self-calibration is performed so that the contour of the statistical shape matches the image contour while the statistical shape is concomitantly optimized...
September 15, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28918955/shifts-in-the-relationship-between-motor-unit-recruitment-thresholds-versus-derecruitment-thresholds-during-fatigue
#5
Matt S Stock, Jacob A Mota
Muscle fatigue is associated with diminished twitch force amplitude. We examined changes in the motor unit recruitment versus derecruitment threshold relationship during fatigue. Nine men (mean age = 26 years) performed repeated isometric contractions at 50% maximal voluntary contraction (MVC) knee extensor force until exhaustion. Surface electromyographic signals were detected from the vastus lateralis, and were decomposed into their constituent motor unit action potential trains. Motor unit recruitment and derecruitment thresholds and firing rates at recruitment and derecruitment were evaluated at the beginning, middle, and end of the protocol...
September 14, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28917828/a-model-of-blood-supply-to-the-brain-via-the-carotid-arteries-effects-of-obstructive-vs-sclerotic-changes
#6
O Onaizah, T L Poepping, M Zamir
The carotid artery is one of the major supply routes of blood to the brain and a common site of vascular disease. Obstructive and sclerotic disorders within the carotid artery impact local blood flow patterns as well as overall impedance and blood supply to the brain. A lumped parameter model and an experimental in-vitro flow loop were used to study the effects of local stenosis and stiffness in the carotid artery based on a family of phantoms with different degrees of stenosis and compliance. The model also allows independent examination of the effects of downstream resistance and compliance...
September 13, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28916208/intra-and-inter-session-reliability-of-traditional-and-entropy-based-variables-describing-stance-on-a-wobble-board
#7
Lucia Bizovska, Miroslav Janura, Zdenek Svoboda, Martin Cerny, Jana Krohova, Maros Smondrk
A wobble board (WB) is a balance rehabilitation tool that is used in physiotherapy to improve strength and stability. The WB tested in this study includes a sensory module for measuring patients' tilt and rotation during stance. The aim of this study was to assess the reliability and validity of a balance measurement using a WB. Thirty healthy young adults participated in this study. The participants stood on the WB to simultaneously record the tilt of the WB and the center of pressure data using a force plate...
September 12, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28890304/hemodynamic-parameters-that-may-predict-false-lumen-growth-in-type-b-aortic-dissection-after-endovascular-repair-a-preliminary-study-on-long-term-multiple-follow-ups
#8
Huanming Xu, Zhenfeng Li, Huiwu Dong, Yilun Zhang, Jianyong Wei, Paul N Watton, Wei Guo, Duanduan Chen, Jiang Xiong
Thoracic endovascular aortic repair (TEVAR) is commonly applied in type-B aortic dissection. For patients with dissection affects descending aorta and extends downward to involve abdominal aorta and possibly iliac arteries, false lumen (FL) expansion might occur post-TEVAR. Predictions of dissection development may assist in medical decision on re-intervention or surgery. In this study, two patients are selected with similar morphological features at initial presentation but with different long-term FL development post-TEVAR (stable and enlarged FL)...
September 7, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28890303/a-simulation-framework-for-humeral-head-translations
#9
Ehsan Sarshari, Alain Farron, Alexandre Terrier, Dominique Pioletti, Philippe Mullhaupt
Humeral head translations (HHT) play a crucial role in the glenohumeral (GH) joint function. The available shoulder musculoskeletal models developed based on inverse dynamics however fall short of predicting the HHT. This study aims at developing a simulation framework that allows forward-dynamics simulation of a shoulder musculoskeletal model with a 6 degrees of freedom (DOF) GH joint. It provides a straightforward solution to the HHT prediction problem. We show that even within a forward-dynamics simulation addressing the HHT requires further information about the contact...
September 7, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28890302/ulna-humerus-contact-mechanics-finite-element-analysis-and-experimental-measurements-using-a-tactile-pressure-sensor
#10
Mohsen Sharifi Renani, Munsur Rahman, Akin Cil, Antonis P Stylianou
Elbow articular cartilage withstands high compressive and shear forces while protecting the bone from excessive loading. Better understanding of elbow cartilage contact mechanics can provide insight into cartilage degeneration. In this study a tactile pressure sensor was used to measure the contact pressure distribution within the ulno-humeral joint of two cadaver specimens at 20° flexion angle across three different axial loads of 80 N, 110 N, and 140 N. Corresponding 3D finite element (FE) models were constructed from magnetic resonance imaging (MRI) and contact analysis was performed for each specimen with boundary and loading conditions identical to the experiment...
September 7, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28888789/modal-analysis-for-the-assessment-of-cementless-hip-stem-primary-stability-in-preoperative-tha-planning
#11
Andres Rondon, Elhadi Sariali, Quentin Vallet, Quentin Grimal
This numerical vibration finite element (FE) study introduces resonance three-dimensional planning (RP3D) to assess preoperatively the primary stability of a cementless stem for total hip arthroplasty. Based on a patient's CT-scan and a numerical model of a stem, RP3D aims at providing mechanical criteria indicative of the achievable primary stability. We investigate variations of the modal response of the stem to changes of area and apparent stiffness of the bone-implant interface. The model is computationally cheap as it does not include a mesh of the bone...
September 6, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28888788/experimental-and-modelling-characterisation-of-adjustable-hollow-micro-needle-delivery-systems
#12
Ting-Ting Liu, Kai Chen, Min Pan
BACKGROUND: Hollow micro-needles have been used increasingly less in practice because the infusion into the skin is limited by the tissue resistance to flow. The relationship between the infusion flow rate and tissue resistance pressure is not clear. METHODS: A custom-made, hollow micro-needle system was used in this study. The driving force and infusion flow rate were measured using a force transducer attached to an infusion pump. Evans blue dye was injected into the air, polyacrylamide gel and in-vivo mouse skin at different flow rates...
September 6, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28888787/radiographic-cup-anteversion-measurement-corrected-from-pelvic-tilt
#13
Liao Wang, Andrew R Thoreson, Robert T Trousdale, Bernard F Morrey, Kerong Dai, Kai-Nan An
The purpose of this study was to develop a novel technique to improve the accuracy of radiographic cup anteversion measurement by correcting the influence of pelvic tilt. Ninety virtual total hip arthroplasties were simulated from computed tomography data of 6 patients with 15 predetermined cup orientations. For each simulated implantation, anteroposterior (AP) virtual pelvic radiographs were generated for 11 predetermined pelvic tilts. A linear regression model was created to capture the relationship between radiographic cup anteversion angle error measured on AP pelvic radiographs and pelvic tilt...
September 6, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28870418/vibration-based-fixation-assessment-of-tibial-knee-implants-a-combined-in-vitro-and-in-silico-feasibility-study
#14
Steven Leuridan, Quentin Goossens, Tom Vander Sloten, Koen De Landsheer, Hendrik Delport, Leonard Pastrav, Kathleen Denis, Wim Desmet, Jos Vander Sloten
The preoperative diagnosis of loosening of cemented tibial knee implants is challenging. This feasibility study explored the basic potential of a vibration-based method as an alternative diagnostic technique to assess the fixation state of a cemented tibia implant and establish the method's sensitivity limits. A combined in vitro and in silico approach was pursued. Several loosening cases were simulated. The largest changes in the vibrational behavior were obtained in the frequency range above 1500 Hz. The vibrational behavior was described with two features; the frequency response function and the power spectral density band power...
September 1, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28870417/characterization-of-an-innovative-intramedullary-nail-for-diaphyseal-fractures-of-long-bones
#15
V Filardi
In this paper, an innovative design of nail for fractures occurring on long bones has been investigated. Its functioning is based essentially on sliding of conical surfaces, located in a spindle and in holding pins. Spindle and holding pins are connected together by a sleeve. The sliding transforms the rotational and translational motion of the spindle to a radial expansion of the holding pins, protruding inside the intramedullary canal. In order to evaluate mechanical behavior of the prosthesis different benchmarks and tests were numerically performed by an FE code...
September 1, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28844415/novel-curved-surface-preparation-technique-for-knee-resurfacing
#16
Jianmo Li, Susannah Clarke, Justin P Cobb, Andrew A Amis
Conventional tools are incapable of preparing the curved articular surface geometry required during cartilage repair procedures. A novel curved surface preparation technique was proposed and tested to provide an accurate low-cost solution. Three shapes of samples, with flat, 30 mm radius and 60 mm radius surfaces, were manufactured from foam bone substitute for testing. Registering guides and cutting guides were designed and 3-D printed to fit onto the foam samples. A rotational cutting tool with an adapter was used to prepare the surfaces following the guidance slots in the cutting guides...
August 22, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28838797/thread-based-microfluidics-flow-patterns-in-homogeneous-and-heterogeneous-microfiber-bundles
#17
J Berthier, K A Brakke, D Gosselin, E Berthier, F Navarro
Thread-based microfluidics has recently seen considerable developments in the domain of portable diagnostic systems, smart bandages and tissue engineering. Similarly to paper-based microfluidics, thread-based microfluidics uses the wicking of fibers to move fluids. It has the advantage of confining and guiding the fluid along the yarns in a one, two or three dimensional space. A global approach to the motion of fluids in yarns and fiber bundles has already been reported in the literature based on the Lucas-Washburn-Rideal law...
August 21, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28826857/3d-reconstruction-of-human-bones-based-on-dictionary-learning
#18
Binkai Zhang, Xiang Wang, Xiao Liang, Jinjin Zheng
An effective method for reconstructing a 3D model of human bones from computed tomography (CT) image data based on dictionary learning is proposed. In this study, the dictionary comprises the vertices of triangular meshes, and the sparse coefficient matrix indicates the connectivity information. For better reconstruction performance, we proposed a balance coefficient between the approximation and regularisation terms and a method for optimisation. Moreover, we applied a local updating strategy and a mesh-optimisation method to update the dictionary and the sparse matrix, respectively...
August 18, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28826570/effect-of-longitudinal-anatomical-mismatch-of-stenting-on-the-mechanical-environment-in-human-carotid-artery-with-atherosclerotic-plaques
#19
Zhenmin Fan, Xiao Liu, Anqiang Sun, Nan Zhang, Zhanming Fan, Yubo Fan, Xiaoyan Deng
Longitudinal anatomic mismatch (LAM) of stenting (i.e., a stenotic artery segment is not fully covered by a deployed stent) worsens the mechanical environment in the treated artery, which most likely is the cause for the associated high risks of restenosis, myocardial infarction and stent thrombosis. To probe the possibility, we constructed a patient-specific carotid model with two components of plaques (lipid and calcified plaque) based on MRI images; we numerically compared three different stenting scenarios in terms of von Mises stress (VMS) distribution in the treated arteries, namely, the short stenting (LAM), the medium stenting and the long stenting...
August 17, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28807513/second-generation-prototype-of-a-variable-stiffness-transverse-plane-adapter-for-a-lower-limb-prosthesis
#20
Corey Pew, Glenn K Klute
The prescription and fitting of a traditional lower limb prosthesis often focuses on straight walking, neglecting maneuvers such as turning and pivoting that require flexibility in the transverse plane. Current devices that allow transverse plane movement only offer a fixed stiffness and are incapable of adapting to varying daily activities. Pilot testing of a first-generation variable stiffness torsion adapter (VSTA I) showed a benefit for individuals with lower limb amputation by reducing peak transverse plane moments at the residual limb which could lead to increased comfort, but testing was limited due to excessive device height and mass...
August 11, 2017: Medical Engineering & Physics
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