Meniscus Position Research Articles

Evaluation of meniscal extrusion with posterior root disruption and repair using ultrasound

BackgroundUltrasound techniques have been utilized for detection of discrete meniscus tears and extrusion. Meniscal extrusion is associated with increased contact pressure and decreased contact area contributing to the advancement of knee osteoarthritis. The purpose of this biomechanical study was to detect meniscal extrusion using a clinically available, portable ultrasound device. And further, to show that extent of injury and a weight-bearing state correlate with amount of extrusion. MethodsA portable, hand-held ultrasound was utilized to image the lateral meniscus in association with (1) an intact posterior root attachment, (2) a 50% cut, (3) a 100% cut, and (4) repaired posterior root attachment. Images were obtained in an unloaded condition, and again under a static, physiologic (70kg) axial load for above injury levels, and again following repair. ResultsSignificant differences in extrusion were noted between the intact and both the 50% cut (p=0.028) and 100% cut groups (p<0.001) all in the loaded position. No significant difference was found in extrusion between intact state and repaired posterior root in the axially loaded position (p=0.174). Both load (p=0.003) and injury level (p=0.005) had significant effects on the mean extrusion of the lateral meniscus. ConclusionSectioning of the lateral meniscus posterior root will produce significantly increased lateral extrusion of the meniscus under physiologic loads. Unlike MRI evaluation, weight-bearing ultrasound images allow a functional assessment of meniscus extrusion. Trans-tibial posterior root repair can restore the lateral meniscus position and integrity. Clinical relevanceThis weight-bearing ultrasound technique can be an important assessment tool for complete evaluation of meniscus injuries.

Operability coating window of dual-layer slot coating process using viscocapillary model

The viscocapillary model for predicting the operability windows in a dual-slot coating process for two Newtonian liquids has been derived by means of a lubrication approximation technique from two-dimensional (2-D) Navier-Stokes equations. The flow rates per width and the pressure differences simplified in several sub-regions within the coating bead regime have been integrated together with approximations of the upstream and downstream menisci and the interlayer between the top and bottom layers. Coating limits or onsets for leaking and bead break-up defects have been determined on the basis of the position of upstream meniscus of the bottom layer as an indicator. Operability coating windows predicted from the viscocapillary model show a good agreement with those by 2-D CFD solver and experiments. In addition, the pressure profiles within the coating bead regime compared between the viscocapillary and 2-D models are qualitatively similar. This simplified model can be applied as a fast tool for usefully manipulating the stable operations in dual-layer slot coating systems.

Quantitative measures of meniscus extrusion predict incident radiographic knee osteoarthritis – data from the Osteoarthritis Initiative

To test the hypothesis that quantitative measures of meniscus extrusion predict incident radiographic knee osteoarthritis (KOA), prior to the advent of radiographic disease. 206 knees with incident radiographic KOA (Kellgren Lawrence Grade (KLG) 0 or 1 at baseline, developing KLG 2 or greater with a definite osteophyte and joint space narrowing (JSN) grade ≥1 by year 4) were matched to 232 control knees not developing incident KOA. Manual segmentation of the central five slices of the medial and lateral meniscus was performed on coronal 3T DESS MRI and quantitative meniscus position was determined. Cases and controls were compared using conditional logistic regression adjusting for age, sex, BMI, race and clinical site. Sensitivity analyses of early (year [Y] 1/2) and late (Y3/4) incidence was performed. Mean medial extrusion distance was significantly greater for incident compared to non-incident knees (1.56 mean±1.12mm SD vs 1.29±0.99mm;+21%, P<0.01), so was the percent extrusion area of the medial meniscus (25.8±15.8% vs 22.0±13.5%;+17%, P<0.05). This finding was consistent for knees restricted to medial incidence. No significant differences were observed for the lateral meniscus in incident medial KOA, or for the tibial plateau coverage between incident and non-incident knees. Restricting the analysis to medial incident KOA at Y1/2 differences were attenuated, but reached significance for extrusion distance, whereas no significant differences were observed at incident KOA in Y3/4. Greater medial meniscus extrusion predicts incident radiographic KOA. Early onset KOA showed greater differences for meniscus position between incident and non-incident knees than late onset KOA.

Longitudinal change in quantitative meniscus measurements in knee osteoarthritis--data from the Osteoarthritis Initiative.

We aimed to apply 3D MRI-based measurement technology to studying 2-year change in quantitative measurements of meniscus size and position. Forty-seven knees from the Osteoarthritis Initiative with medial radiographic joint space narrowing had baseline and 2-year follow-up MRIs. Quantitative measures were obtained from manual segmentation of the menisci and tibia using coronal DESSwe images. The standardized response mean (SRM = mean/SD change) was used as measure of sensitivity to longitudinal change. Medial tibial plateau coverage decreased from 34.8% to 29.9% (SRM -0.82; p < 0.001). Change in medial meniscus extrusion in a central image (SRM 0.18) and in the central five slices (SRM 0.22) did not reach significance, but change in extrusion across the entire meniscus (SRM 0.32; p = 0.03) and in the relative area of meniscus extrusion (SRM 0.56; p < 0.001) did. There was a reduction in medial meniscus volume (10%; p < 0.001), width (7%; p < 0.001), and height (2%; p = 0.08); meniscus substance loss was strongest in the posterior (SRM -0.51; p = 0.001) and weakest in the anterior horn (SRM -0.15; p = 0.31). This pilot study reports, for the first time, longitudinal change in quantitative 3D meniscus measurements in knee osteoarthritis. It provides evidence of improved sensitivity to change of 3D measurements compared with single slice analysis. • First longitudinal MRI-based measurements of change of meniscus position and size. • Quantitative longitudinal evaluation of meniscus change in knee osteoarthritis. • Improved sensitivity to change of 3D measurements compared with single slice analysis.

Improved precision of hydraulic conductance measurements using a Cochard rotor in two different centrifuges

An improved way ofcalculating hydraulic conductance (K) in a Cochard cavitron is described. UsuallyK is determined by measuring how fast water levels equilibrate between two reservoirs while a stem spins in a centrifuge. A regression of log meniscus position versus time was used to calculate K and this regression method was compared to the old technique that takes the average of discrete values. Results of a hybrid Populus 84K shows that the relative error of the new approach is significantly lower than the old technique by 4~5 times. The new computational method results in a relative error less than 0.5% or 0.3% from 8 or 12 points of measurement, respectively. The improved precision of K measurement also requires accurate assessment of stem temperature because temperature changes K by 2.4% oC-1. A computational algorithm for estimating stem temperature stability in a cavitron rotor was derived. This algorithm provides information on how long it takes stem temperature to be known to within an error of ±0.1oC.

On the meniscus formation and the negative hydrogen ion extraction from ITER neutral beam injection relevant ion source

The development of a large area (Asource,ITER = 0.9 × 2 m2) hydrogen negative ion (NI) source constitutes a crucial step in construction of the neutral beam injectors of the international fusion reactor ITER. To understand the plasma behaviour in the boundary layer close to the extraction system the 3D PIC MCC code ONIX is exploited. Direct cross checked analysis of the simulation and experimental results from the ITER-relevant BATMAN source testbed with a smaller area (Asource,BATMAN ≈ 0.32 × 0.59 m2) has been conducted for a low perveance beam, but for a full set of plasma parameters available. ONIX has been partially benchmarked by comparison to the results obtained using the commercial particle tracing code for positive ion extraction KOBRA3D. Very good agreement has been found in terms of meniscus position and its shape for simulations of different plasma densities. The influence of the initial plasma composition on the final meniscus structure was then investigated for NIs. As expected from the Child–Langmuir law, the results show that not only does the extraction potential play a crucial role on the meniscus formation, but also the initial plasma density and its electronegativity. For the given parameters, the calculated meniscus locates a few mm downstream of the plasma grid aperture provoking a direct NI extraction. Most of the surface produced NIs do not reach the plasma bulk, but move directly towards the extraction grid guided by the extraction field. Even for artificially increased electronegativity of the bulk plasma the extracted NI current from this region is low. This observation indicates a high relevance of the direct NI extraction. These calculations show that the extracted NI current from the bulk region is low even if a complete ion–ion plasma is assumed, meaning that direct extraction from surface produced ions should be present in order to obtain sufficiently high extracted NI current density. The calculated extracted currents, both ions and electrons, agree rather well with the experiment.

Evidence of slippage breakdown for a superhydrophobic microchannel

A full characterization of the water flow past a silicon superhydrophobic surface with longitudinal micro-grooves enclosed in a microfluidic device is presented. Fluorescence microscopy images of the flow seeded with fluorescent passive tracers were digitally processed to measure both the velocity field and the position and shape of the liquid-air interfaces at the superhydrophobic surface. The simultaneous access to the meniscus and velocity profiles allows us to put under a strict test the no-shear boundary condition at the liquid-air interface. Surprisingly, our measurements show that air pockets in the surface cavities can sustain non-zero interfacial shear stresses, thereby hampering the friction reduction capabilities of the surface. The effects of the meniscus position and shape as well as of the liquid-air interfacial friction on the surface performances are separately assessed and quantified.

Characteristics of air entrainment during dynamic wetting failure along a planar substrate

AbstractCharacteristic substrate speeds and meniscus shapes associated with the onset of air entrainment are studied during dynamic wetting failure along a planar substrate. Using high-speed video, the behaviour of the dynamic contact line (DCL) is recorded as a tape substrate is drawn through a bath of a glycerol/water solution. Air entrainment is identified by triangular air films that elongate from the DCL above some critical substrate speed. Meniscus confinement within a narrow gap between the substrate and a stationary plate is shown to delay air entrainment to higher speeds for a wide range of liquid viscosities, expanding upon the findings of Vandre, Carvalho &amp; Kumar (J. Fluid Mech., vol. 707, 2012, pp. 496–520). A pressurized liquid reservoir controls the meniscus position within the confinement gap. It is found that liquid pressurization further postpones air entrainment when the meniscus is located near a sharp corner along the stationary plate. Meniscus shapes recorded near the DCL demonstrate that operating conditions influence the size of entrained air films, with smaller films appearing in the more viscous solutions. Regardless of size, air films become unstable to thickness perturbations and ultimately rupture, leading to the entrainment of air bubbles. Recorded critical speeds and air-film sizes compare well to predictions from a hydrodynamic model for dynamic wetting failure, suggesting that strong air stresses near the DCL trigger the onset of air entrainment.

Inverse Problem of Capillary Filling

The inverse problem of capillary filling, as defined in this work, consists in determining the capillary radius profile from experimental data of the meniscus position l as a function of time t. This problem is central in diverse applications, such as the characterization of nanopore arrays or the design of passive transport in microfluidics; it is mathematically ill posed and has multiple solutions; i.e., capillaries with different geometries may produce the same imbibition kinematics. Here a suitable approach is proposed to solve this problem, which is based on measuring the imbibition kinematics in both tube directions. Capillary filling experiments to validate the calculation were made in a wide range of length scales: glass capillaries with a radius of around 150 μm and anodized alumina membranes with a pores radius of around 30 nm were used. The proposed method was successful in identifying the radius profile in both systems. Fundamental aspects also emerge in this study, notably the fact that the l(t)∝t1/2 kinematics (Lucas-Washburn relation) is not exclusive of uniform cross-sectional capillaries.

Relationship betweeen subregional longitudinal cartilage loss and meniscus position in knees with and without joint space narrowing – Data from the osteoarthritis initiative

Relationship betweeen subregional longitudinal cartilage loss and meniscus position in knees with and without joint space narrowing – Data from the osteoarthritis initiative

On the thermodynamic theory of the strength of solids: 4. Capillary condensation and capillary evaporation in wedge-shaped crack

The processes of capillary condensation and capillary evaporation in a wedge-shaped crack are considered. Capillary evaporation is a comparatively new phenomenon that is opposite to capillary condensation and occurs upon the cleavage of a solid in a nonwetting liquid. For both cases, the positions of a meniscus inside a wedge-shaped crack have been calculated as functions of the meniscus curvature radius, liquid-contact angle, and crack-opening angle. The effect of temperature on the meniscus position has been analyzed; it has been established that the meniscus shifts from the gaseous toward the liquid phase as temperature rises. The regularities of meniscus displacements in the course of crack growth have been established: under the conformal mechanism of crack growth, the absolute position of the meniscus remains unchanged (i.e., the meniscus and the crack frontal line move at the same velocity), while, under the depth mechanism of growth, the relative position of the meniscus is retained.

Gravity and capillary pressure-driven drainage in a vertical Hele-Shaw cell: Thin film deposition

The stable-downward vertical displacement of an air–liquid meniscus in a two-dimensional Hele-Shaw cell is studied in the limit of small capillary (Ca⁎) and Bond (BoH⁎) numbers. Subsequently, a thin film of thickness h is deposited on the substrate walls for Ca⁎⪯¡BoH⁎. Using a reverse Washburn analysis as it applies to two-dimensional geometries in the Stokes flow limit, we develop mathematical expressions for the speed of the average location of the meniscus x¯N spanning the smallest gap dimension a. Furthermore, we show that the other spanwise meniscus is stable using classic linear stability analysis for immiscible fluid displacements. Asymptotic analysis of the average meniscus speed yields an expression for the film thickness as a function of several measurable parameters. Experiments are performed using silicone oil (kinematic viscosities 1×10−5, 1×10−4 and 1×10−3 m2/s) while varying the initial displacement height of the meniscus before descent x¯N0, and the Hele-Shaw cell gap spacing. Analysis of the transient film thickness h, estimated from the average meniscus position, speed and physical properties, is in good agreement and suggests self-similarity.

3D numerical simulations of negative hydrogen ion extraction using realistic plasma parameters, geometry of the extraction aperture and full 3D magnetic field map

Decreasing the co-extracted electron current while simultaneously keeping negative ion (NI) current sufficiently high is a crucial issue on the development plasma source system for ITER Neutral Beam Injector. To support finding the best extraction conditions the 3D Particle-in-Cell Monte Carlo Collision electrostatic code ONIX (Orsay Negative Ion eXtraction) has been developed. Close collaboration with experiments and other numerical models allows performing realistic simulations with relevant input parameters: plasma properties, geometry of the extraction aperture, full 3D magnetic field map, etc. For the first time ONIX has been benchmarked with commercial positive ions tracing code KOBRA3D. A very good agreement in terms of the meniscus position and depth has been found. Simulation of NI extraction with different e/NI ratio in bulk plasma shows high relevance of the direct negative ion extraction from the surface produced NI in order to obtain extracted NI current as in the experimental results from BATMAN testbed.

Contribution of regional 3D meniscus and cartilage morphometry by MRI to joint space width in fixed flexion knee radiography—A between-knee comparison in subjects with unilateral joint space narrowing

BackgroundRadiographic joint space width (JSW) is considered the reference standard for demonstrating structural therapeutic benefits in knee osteoarthritis. Our objective was to determine the proportion by which 3D (regional) meniscus and cartilage measures explain between-knee differences of JSW in the fixed flexion radiographs. MethodsSegmentation of the medial meniscus and tibial and femoral cartilage was performed in double echo steady state (DESS) images. Quantitative measures of meniscus size and position, femorotibial cartilage thickness, and radiographic JSW (minimum, and fixed locations) were compared between both knees of 60 participants of the Osteoarthritis Initiative, with strictly unilateral medial joint space narrowing (JSN). Statistical analyses (between-knee, within-person comparison) were performed using regression analysis. ResultsA strong relationship with side-differences in minimum and a central fixed location JSW was observed for percent tibial plateau coverage by the meniscus (r=.59 and .47; p<.01) and central femoral cartilage thickness (r=.69 and .75; p<.01); other meniscus and cartilage measures displayed lower coefficients. The correlation of central femoral cartilage thickness with JSW (but not that of meniscus measures) was greater (r=.78 and .85; p<.01) when excluding knees with non-optimal alignment between the tibia and X-ray beam. Conclusion3D measures of meniscus and cartilage provide significant, independent information in explaining side-differences in radiographic JSW in fixed flexion radiographs. Tibial coverage by the meniscus and central femoral cartilage explained two thirds of the variability in minimum and fixed location JSW. JSW provides a better representation of (central) femorotibial cartilage thickness, when optimal positioning of the fixed flexion radiographs is achieved.

Effect of sloped die lip geometry on the operability window in slot coating flows using viscocapillary and two-dimensional models

As an indicator for determining the operability window in slot coating flow, the viscocapillary model considering various configurations of upstream and downstream slot die lips was tested and compared with Navier–Stokes two-dimensional model. Bead pressure and sloped lip angle conditions for uniform coating operation demarcated from leaking and bead break-up defects were quantitatively predicted from the position of upstream meniscus from both models. By comparing the results, it is confirmed that the viscocapillary model for many kinds of sloped die lips could predict the operability window accurately. It is also found that there exists vortex or recirculation regimes inside upstream and downstream coating bead regions, depending on the angles of sloped die lips, even for the stable coating flow. The flow control by die lip structure will be usefully applied to design the strategy for the reliable and optimal coating process, including vortex-free windows.

A single channel capillary microviscometer

We have developed a microviscometer analyzing the fluid dynamics in a single channel glass microfluidic chip with a closed end. The device is able to test sample volumes of a few microliters by inserting one drop in the inlet. The fluid enters the channel driven by capillary pressure and an optical sensor registers the motion. The equation that describes the fluid dynamics is function of the channel geometry, atmospheric pressure, fluid viscosity, and capillary pressure. Knowing the first two, the last parameters can be obtained as fitting parameters from the meniscus position as a function of time plot. We have successfully tested Newtonian fluids with different viscosities and capillary pressure.

Tibial coverage, meniscus position, size and damage in knees discordant for joint space narrowing – data from the Osteoarthritis Initiative

Meniscal extrusion is thought to be associated with less meniscus coverage of the tibial surface, but the association of radiographic disease stage with quantitative measures of tibial plateau coverage is unknown. We therefore compared quantitative and semi-quantitative measures of meniscus position and morphology in individuals with bilateral painful knees discordant on medial joint space narrowing (mJSN). A sample of 60 participants from the first half (2,678 cases) of the Osteoarthritis Initiative cohort fulfilled the inclusion criteria: bilateral frequent pain, Osteoarthritis Research Society International (OARSI) mJSN grades 1-3 in one, no-JSN in the contra-lateral (CL), and no lateral JSN in either knee (43 unilateral mJSN1; 17 mJSN2/3; 22 men, 38 women, body mass index (BMI) 31.3±3.9kg/m(2)). Segmentation and three-dimensional quantitative analysis of the tibial plateau and meniscus, and semi-quantitative evaluation of meniscus damage (magnetic resonance imaging (MRI) osteoarthritis knee score=MOAKS) was performed using coronal 3T MR images (MPR DESSwe and intermediate-weighted turbo spin echo (IW-TSE) images). CL knees were compared using paired t-tests (between-knee, within-person design). Medial tibial plateau coverage was 36±9% in mJSN1 vs 45±8% in CL no-JSN knees, and was 31±9% in mJSN2/3 vs 46±6% in no-JSN knees (both P<0.001). mJSN knees showed greater meniscus extrusion and damage (MOAKS), but no significant difference in meniscus volume. No significant differences in lateral tibial coverage, lateral meniscus morphology or position were observed. Knees with medial JSN showed substantially less medial tibial plateau coverage by the meniscus. We suggest that the less meniscal coverage, i.e., less mechanical protection may be a reason for greater rates of cartilage loss observed in JSN knees.

Evaluation of medial meniscus tears and meniscal stability: Weight-bearing MRI vs arthroscopy

To assess the role of dedicated low-field standard and weight-bearing MRI in the evaluation of stable or unstable tears of medial meniscus in comparison with arthroscopy.Our series included 1750 knee MRI scans performed with a high-field MRI scanner from July 2010 to August 2011. We retrospectively reviewed and analyzed 20 MRI exams of normal knee and 57 MRI exams of knee with clinical evidence of tears of the medial meniscus. In the same session, after conventional 1.5T and “dedicated” 0.25T supine MRI exam, the patients underwent weight-bearing examination with the same dedicated MRI unit. In all cases sagittal and coronal PD-W were used. All patients underwent arthroscopy 18–25 days after the weight-bearing MRI. In the first group, no statistically significant anatomical modifications of shape, intensity and position of the medial meniscus between standard 1.5T, dedicated supine and upright MRI were observed. In group A, the images acquired in the supine position (dedicated and 1.5T MRI) documented in 21 cases a traumatic tear (group 2A) and in 36 cases a degenerative tear (group 2B). In group 2A, weight-bearing MRI showed presence of unstable tear a degenerative unstable meniscal tear only in 19 out of 36 cases. In group 2B, weight-bearing MRI showed only in 9 out 21 cases. Arthroscopy confirmed weight-bearing MRI diagnosis in all cases.This new approach to meniscus pathology gives an important contribution to a better management of a diagnostic–therapeutic approach in which standard MRI has not played a key role, so far.

Capillary collapse of a micro-double cantilever beam: a rigorous study

High-aspect-ratio microstructures have been found, in the literature, to collapse due to capillary forces of liquids. In this paper, mathematical models are developed to study the collapse of a microstructure represented by a double cantilever beam (DCB) with a liquid droplet located at the free end. Formulations are presented using the classical Bernoulli–Euler beam theory as well as an analysis that accounts for geometrical nonlinearity. The models introduce rigorous coupling between the DCB deformation, the capillary forces, and the meniscus position, and have predicted interesting nonlinear behaviors that previous models could not. Parameters governing the capillary collapse of the DCB are identified, and their influence is discussed. A single dimensionless number that controls the condition for collapse is proposed and validated against numerical results. Comparison between the linear and nonlinear beam analyses shows that linear analysis generally suffices for the description of capillary collapse of microstructures.

Multiphase capillary rise of multicomponent miscible liquids

The rise of the two-phase (gas and liquid) and two-component (water and ethanol) system in uniform capillaries was analysed by coupling earlier experimental data and a mathematical framework for multiphase capillary rise. These were used to determine how the meniscus position, velocity and acceleration were affected by the physical, chemical and thermodynamic parameters of miscible liquid components. These analyses demonstrated that these parameters could be determined from those of the pure substances, and allowed predicting the system state with residuals less than 1.6%. However, nonlinearities were not anticipated in the way thermodynamic parameters affected the meniscus velocity. Specifically, dynamic contact angle at the three-phase contact line was dominated by the meniscus velocity at low ethanol concentrations and by the thermodynamic parameters at high ethanol concentrations. The hypothesis by which regression equations are used to describe the dynamic contact angle is therefore rejected in favor of mechanistic equations, which may be used for an interpretation of the rise of liquids made of multiple miscible components.