Meniscus Surface Research Articles

DYNAMIC CONTACT MECHANICS IN THE OVINE KNEE JOINT FOLLOWING PARTIAL MENISCECTOMY

Meniscus tears occur in up to one third of all sports injuries and 60% of patients over 65 years. Meniscus tears increase knee joint contact pressure and the risk of developing early osteoarthritis (OA). Integrating juxtaposed meniscus surfaces continues to be a challenge during meniscal repair. Partial meniscectomy is a common surgical procedure for meniscal tear, especially in the non-vascularized white-white zone. Most studies on the effects of size and location of partial meniscectomy on knee joint contact pressures simulated the standing posture and some static angles of flexion (30° and 60°). Information on the safe proportion and location of a partial meniscectomy that would maintain knee joint contact stresses close to those in the healthy joint during dynamic loading is not known. The aim of this study is to investigate the relationship between partial meniscectomy size and location with the corresponding knee joint contact pressures during dynamic loading, emulating activities of daily living. We hypothesize that partial meniscectomy size increases knee joint contact pressure.

Meniscal Repair

The surgical techniques and associated devices for meniscus repair have improved over time, spurred in part by the clear recognition of the benefits of meniscal preservation and in part by the introduction of ultra-high-molecular weight polyethylene containing sutures. The desires for more minimally invasive techniques that decrease the risks of neurovascular injury and articular cartilage excoriation have seen 1 device generation after another introduced and improved upon. The current generation of meniscal repair all-inside devices are easier to use, limit the presence of material on the meniscal surface, and are self-adjusting and suture based. Although the speed of meniscus fixation device development places increasingly useful devices in surgeons' hands, clinical evidence of their effectiveness lag behind.

Accuracy of MRI in the Diagnosis of Meniscal Tears in Older Patients

The objective of our study was to determine the accuracy of MRI in diagnosing meniscal tears in older patients and the frequency with which abnormal MRI findings correlate with degeneration, fraying, and tears at arthroscopy. Ninety-two patients 50 years old or older who had undergone knee MRI followed by knee arthroscopy within 6 months were selected. Menisci were graded on a 5-point scale: 1, definitely no tear; 2, probably no tear; 3, indeterminate or equivocal; 4, probably a tear; and 5, definitely a tear. Meniscal signal changes, meniscal surface morphology, and extrameniscal abnormalities were noted. Operative notes were reviewed, and the sensitivity and specificity of MRI results were calculated. For medial tears, MRI had a sensitivity and specificity of 0.91 and 0.94, respectively, when grade 5 was considered a tear, 0.96 and 0.76 when grades 4 and 5 were considered a tear, and 0.99 and 0.47 when grades 3-5 were considered a tear. For lateral tears, MRI had a sensitivity and specificity of 0.73 and 0.91 when grade 5 was considered a tear, 0.88 and 0.80 when grades 4 and 5 were considered a tear, and 1.0 and 0.61 when grades 3-5 were considered a tear. The positive predictive values (PPVs) of MRI for the medial meniscus were 99%, grade 5; 57%, grade 4; 29%, grade 3; 25%, grade 2; and 0%, grade 1. For the lateral meniscus, the PPVs of MRI were 76%, grade 5; 36%, grade 4; 19%, grade 3; and 0%, grades 1 and 2. The accuracy of MRI for diagnosing meniscal tears in older patients is high and similar to that in younger patients when only definitive findings are considered a tear. The specificity decreases if equivocal or probable findings are considered a tear.

Effect of Ionic Transport and Separation on the Meniscus in Molten Carbonate Electrolyte

AbstractMigrational separation due to differences in cationic mobility is commonly observed during current passage in molten carbonate mixtures, and this might be responsible for the improved wetting observed upon polarization, as found experimentally according to the literature. To check this, a 2D transport model based on concentrated‐solution theory was applied to analyze the movement of ions in and near the meniscus. The effect of differences in cationic mobility and of ionic transport in general on current distribution, reaction rate, and electrolyte composition in the meniscus region was quantified, and corresponding surface tension gradients over the meniscus surface predicted. The resulting surface tension gradients were found to be too small to account for the experimentally observed meniscus rise. It is, therefore, concluded that the polarization effect on electrode wetting is not due to the gradient of surface tension caused by cationic separation. A plausible alternative explanation is that a gradient of the S/L interfacial tension exists but that this is due to specifically adsorbed intermediate reaction products, in particular oxides. Such a current density dependent adsorption layer would be in dynamic equilibrium with the local melt composition, and, thereby, drive the wetting/dewetting of the electrode surface that is experimentally observed.

Novel quantitative imaging for early detection of joint tissue injury to support early treatment strategies.

The Cartilage Restoration Center at the University of Pittsburgh conducts research using novel imaging technologies to detect early microstructural changes to articular joint tissues in degenerative and traumatic injury-induced articular cartilage and meniscus disease. Identification of early changes to joint tissues permits the identification of patients who could potentially benefit from therapeutic interventions. Quantitative strategies for the diagnosis and staging of joint tissue degeneration prior to the breakdown of the articular cartilage or meniscal surfaces remain a challenge. Our research has shown that the current clinical standard, arthroscopic visualization, and palpation of cartilage and menisci, may be insensitive to early subsurface alterations in these tissues, particularly in the deepest layers of articular cartilage [1–3]. Our work with quantitative Magnetic Resonance Imaging (MRI) and Optical Coherence Tomography (OCT) reveals a strong potential for these methods to provide information regarding early diagnosis and staging of subsurface tissue injury that are not readily available with current technologies [3–5].

Modeling of primary dendrite arm spacing variations in thin-slab casting of low carbon and low alloy steels

Solidification structure of a High Strength Low Alloy (HSLA) steel, in terms of dendrite arm spacing distribution across the shell thickness, is studied in a breakout shell from a thin-slab caster at Tata Steel in IJmuiden. Columnar dendrites were found to be the predominant morphology throughout the shell with size variations across the shell thickness. Primary Dendrite Arm Spacing (PDAS) increases by increasing the distance from meniscus or slab surface. Subsequently, a model is proposed to describe the variation of the PDAS with the shell thickness (the distance from slab surface) under solidifiction conditions experienced in the primary cooling zone of thin-slab casting. The proposed relationship related the PDAS to the shell thickness and, hence, can be used as a tool for predicting solidifcation structure and optimizing the thin-slab casting of low alloy steels.

Meniscal Morphologic Changes on Magnetic Resonance Imaging Are Associated With Symptomatic Discoid Lateral Meniscal Tear in Children

To determine whether meniscal deformation and displacement on magnetic resonance imaging (MRI) are associated with tears by use of arthroscopic findings as a standard of reference in children with discoid lateral meniscus (DLM). We reviewed MRI scans and intraoperative videos of 69 consecutive patients (79 knees) treated arthroscopically for suspicious DLM tears. The mean age at surgery was 10.9 years (range, 4.3 to 17.6 years). Signal changes and morphologic changes (deformation or displacement) of DLM on magnetic resonance (MR) images were graded by 2 independent observers using our modifications of previously described classification schemes, and then the grades were determined by consensus of the observers. Meniscal tears were assessed by an observer, blinded to the MRI studies, based on arthroscopic findings. Signal changes and morphologic changes of DLM on MR images were correlated with tears. Tears were found more frequently in menisci showing morphologic changes on MR images (P = .001). Of the 25 menisci with a grade 3 signal change (linear or band-like signal intensity extending to the superior or inferior meniscal surface), 24 had tears, and a horizontal cleavage was the most commonly associated tear type. Of the 50 menisci with a grade 1 (dot-like intrameniscal signal change), grade 2 (linear or band-like intrameniscal signal change), or diffuse signal change, 34 were morphologically changed on MR images, and 29 of these (85%) were torn, whereas 9 of the 16 menisci (56%) not morphologically changed were torn (P = .036). Preoperative MRI evaluations based on signal intensities do not accurately predict the presence of a DLM tear in children, except when a DLM shows a grade 3 signal change. Meniscal deformation or displacement observed on preoperative MR images suggests a higher risk of meniscal tears, even in menisci with signal changes other than grade 3 changes. Level IV, therapeutic case series.

Revision 1 Size and position of the healthy meniscus, and its Correlation with sex, height, weight, and bone area- a cross-sectional study

BackgroundMeniscus extrusion or hypertrophy may occur in knee osteoarthritis (OA). However, currently no data are available on the position and size of the meniscus in asymptomatic men and women with normal meniscus integrity.MethodsThree-dimensional coronal DESSwe MRIs were used to segment and quantitatively measure the size and position of the medial and lateral menisci, and their correlation with sex, height, weight, and tibial plateau area. 102 knees (40 male and 62 female) were drawn from the Osteoarthritis Initiative "non-exposed" reference cohort, including subjects without symptoms, radiographic signs, or risk factors for knee OA. Knees with MRI signs of meniscus lesions were excluded.ResultsThe tibial plateau area was significantly larger (p < 0.001) in male knees than in female ones (+23% medially; +28% laterally), as was total meniscus surface area (p < 0.001, +20% medially; +26% laterally). Ipsi-compartimental tibial plateau area was more strongly correlated with total meniscus surface area in men (r = .72 medially; r = .62 laterally) and women (r = .67; r = .75) than contra-compartimental or total tibial plateau area, body height or weight. The ratio of meniscus versus tibial plateau area was similar between men and women (p = 0.22 medially; p = 0.72 laterally). Tibial coverage by the meniscus was similar between men and women (50% medially; 58% laterally), but "physiological" medial meniscal extrusion was greater in women (1.83 ± 1.06mm) than in men (1.24mm ± 1.18mm; p = 0.011).ConclusionsThese data suggest that meniscus surface area strongly scales with (ipsilateral) tibial plateau area across both sexes, and that tibial coverage by the meniscus is similar between men and women.

422 AUTOMATIC SEGMENTATION OF BONE AND CARTILAGE FROM KNEE MRI

greater in healthy women (1.82±1.03mm) than in healthy men (1.19mm±1.26mm; p < 0.01). Conclusions: The ratio between meniscus surface area and (ipsicompartimental) tibial bone area may provide a useful measure for comparing meniscus size across different cohorts with mixed sexes, for instance when testing whether knees with OA display meniscus hypertrophy. Although tibial plateau coverage by the meniscus is similar in healthy men and women, medial meniscus extrusion was greater in women, which may provide potential clues as to why women are at greater risk of symptomatic knee OA than men.

Lubricin distribution in the torn human anterior cruciate ligament and meniscus

The objective of this study was to: (1) determine the distribution of lubricin in the human torn anterior cruciate ligament (ACL) and meniscus; (2) determine the distribution of lubricin in the human intact ACL and meniscus; (3) and identify potential cellular sources of lubricin in these tissues. Ten torn ACLs and six torn menisci were obtained from surgeries; for comparison, 11 intact ACLs and 13 intact menisci were obtained from total knee replacements. Samples were formalin fixed and processed for immunohistochemical staining with a monoclonal antibody for lubricin. In torn ACLs and menisci, lubricin was generally found as a discrete layer covering the torn surface. No surface lubricin staining was found on the transected edges produced during excision. Lubricin was also found on the native surfaces of intact ACLs and menisci. In all tissues, lubricin was found in the matrix and intracellularly. The surface layer of lubricin coating torn edges of ACLs and menisci may interfere with the integrative healing process needed for repair.

Macroscopic and histopathologic analysis of human knee menisci in aging and osteoarthritis

Meniscus lesions following trauma or associated with osteoarthritis (OA) have been described, yet meniscus aging has not been systematically analyzed. The objectives of this study were to (1) establish standardized protocols for representative macroscopic and microscopic analysis, (2) improve existing scoring systems, and (3) apply these techniques to a large number of human menisci. Medial and lateral menisci from 107 human knees were obtained and cut in two different planes (triangle/cross section and transverse/horizontal section as well) in three separate locations (middle portion, anterior and posterior horns). All sections included vascular and avascular regions and were graded for (1) surface integrity, (2) cellularity, (3) matrix/fiber organization and collagen alignment, and (4) Safranin-O staining intensity. The cartilage in all knee compartments was also scored. The new macroscopic and microscopic grading systems showed high inter-reader and intra-reader intraclass correlation coefficients. The major age-related changes in menisci in joints with no or minimal OA included increased Safranin-O staining intensity, decreased cell density, the appearance of acellular zones, and evidence of mucoid degeneration with some loss of collagen fiber organization. The earliest meniscus changes occurred predominantly along the inner rim. Menisci from OA joints showed severe fibrocartilaginous separation of the matrix, extensive fraying, tears and calcification. Abnormal cell arrangements included decreased cellularity, diffuse hypercellularity along with cellular hypertrophy and abnormal cell clusters. In general, the anterior horns of both medial and lateral menisci were less affected by age and OA. New standardized protocols and new validated grading systems allowed us to conduct a more systematic evaluation of changes in aging and OA menisci at a macroscopic and microscopic level. Several meniscus abnormalities appear to be specific to aging in the absence of significant OA. With aging the meniscal surface can be intact but abnormal matrix organization and cellularity were observed within the meniscal substance. The increased Safranin-O staining appears to represent a shift from fibroblastic to chondrocytic phenotype during aging and early degeneration.

Effect of chain length of self-assembled monolayers in dip-pen nanolithography using molecular dynamics simulations

The pattern transfer mechanism of an alkanethiol self-assembled monolayer (SAM) with different chain lengths during the dip-pen nanolithography (DPN) process and pattern characterizations are studied using molecular dynamics (MD) simulations. The mechanisms of molecular transference, alkanethiol meniscus characteristics, surface adsorbed energy, transfer number, and pattern formation are evaluated during the DPN process at room temperature. The simulation results clearly show that the molecular transfer ability in DPN is strongly dependent on the chain length. Shorter molecules have significantly better transport and diffusion abilities between the meniscus and substrate surface, and the transport period can be maintained longer. The magnitude of adsorbed energy increases with chain length, so many more molecules can be transferred to the surface when shorter molecules are used. After deposition, the magnitude of the adsorbed area and pattern height decrease with increasing chain length.

Atomic force microscopy of menisci of free-standing smectic films

The profile of menisci of freely suspended smectic films is studied by atomic force microscopy and optical interferometry. The measured meniscus profiles show two distinct regions: a circular shape in thicker regions and an almost linear slope near the edge of the planar film area. A macroscopic contact angle of several degrees is found between the meniscus and flat film. In the smectic C phase and in smectic A close to a transition to smectic C, film menisci are decorated by a characteristic stripe pattern that was first described by Meyer and Pershan [Solid State Commun., 1973, 13, 989–992]. We find that the periodically distorted director field of these structures is accompanied by remarkable undulations of the meniscus surface, with height modulations of a few percent of the stripe period. By comparison of detailed features of AFM and polarization microscopy images, we reveal their correlation with the director structures. We collect arguments against the validity of the classical surface splay model.

Probing forces of menisci: what levels are safe for arthroscopic surgery

PurposeTo facilitate effective learning, feedback on performance during arthroscopic training is essential. Less attention has been paid to feedback on monitoring safe handling of delicate tissues such as meniscus. The goal is to measure in vitro probing forces of menisci and compare them with a theoretical maximum probing force (TMPF).MethodMenisci samples of ten cadavers were mounted on force platforms to measure probing forces up to 20 N in three directions. Nineteen subjects participated: six novices (experience <60 arthroscopies), ten intermediates (>60 arthroscopies), and three faculty (>250 a year). All had to perform three tasks on each meniscus sample with an arthroscopic probe: push three times on the superior meniscal surface, perform one continuous run on the superior meniscal surface, and push three times on the inferior meniscal surface. The absolute maximum probing force (AMPF) was determined for each condition. A multivariable linear regression analysis was performed to assess the influence of experience on the force magnitude (P < 0.05). AMPFs were compared to the TMPF (estimated to be 8.5 N).ResultsThe AMPF of the push task was on average 2.8 N (standard deviation (SD) of 0.8 N), of the continuous run task 2.5 N (SD 0.9 N), and of the pull task 3.9 N (SD 2.0 N). Significant difference was present between experts and novices (P < 0.05). The AMPFs are in the same order of magnitude as the TMPF.ConclusionThe results indicate the necessity of using a safety level for tissue manipulation when training arthroscopy and a value for is magnitude.

Dynamic flow measurements of capillary underfill through a bump array in flip chip package

This study investigated the dynamic variations of flow and meniscus during underfill process using flow visualization techniques to understand physics of capillary flows. For the quantitative flow visualization, a high speed micro particle image velocimetry (μPIV) was applied to a transparent flip chip specimen with arrayed bump structure. As an underfill liquid, glycerin was filled into the flip chip specimen by capillary action. The present visualization technique offers time-varying movement of meniscus and phase-locked velocity fields frozen to the meniscus position. To observe the dynamic contact angle between parallel plates, an in situ measurement technique was developed in the present study. Then, the filling time was compared with analytical models. From this experiment, it was found that the meniscus velocity and the contact angle vary in-phase according to the position of meniscus. The phase-locked velocity fields show velocity gradients on the meniscus surface which gives rise to the breakdown of equilibrium contact angle. Consequently, the detailed filling time has different behavior from the analytical models.

A three‐dimensional quantitative method to measure meniscus shape, position, and signal intensity using MR images: A pilot study and preliminary results in knee osteoarthritis

This pilot study presents a technique for three-dimensional and quantitative analysis of meniscus shape, position, and signal intensity and compares results in knees with (n = 20) and without (n = 11) radiographic osteoarthritis. 3-T MR images with 2mm section thickness were acquired using a proton density-weighted, fat-suppressed, coronal, fast spin-echo sequence. Segmentation of the tibial, femoral, and external surface of the medial meniscus and the tibial joint surface was performed. Three-dimensional parameters were computed to describe the shape, position, and signal intensity of the entire meniscus and three subregions (body, anterior, and posterior horn). Key results included a greater size (i.e., volume, surface areas, and thickness), increased medial extrusion (i.e., greater extrusion distance, greater meniscal area uncovered by tibial surface), and elevated signal intensity of the medial meniscus in osteoarthritis than in nonosteoarthritis knees, particularly in the meniscus body. These results need to be confirmed in larger cohorts, preferably under weight-bearing conditions.

Repair of meniscal cartilage white zone tears using a stem cell/collagen-scaffold implant

Injuries to the avascular region of knee meniscal cartilage do not heal spontaneously. To address this problem we have developed a new stem cell/collagen-scaffold implant system in which human adult bone marrow mesenchymal stem cells are seeded onto a biodegradable scaffold that allows controlled delivery of actively dividing cells to the meniscus surface. Sandwich constructs of two white zone ovine meniscus discs with stem cell/collagen-scaffold implant in between were cultured in vitro for 40 days. Histomorphometric analysis revealed superior integration in the stem cell/collagen-scaffold groups compared to the cell-free collagen membrane or untreated controls. The addition of TGF-β1 to differentiate stem cells to chondrocytes inhibited integration. Biomechanical testing demonstrated a significant 2-fold increase in tensile strength in all constructs using the stem cell/collagen-scaffold compared to control groups after 40 days in culture. Integration was significantly higher when collagen membranes were used that had a more open/spongy structure adjacent to both meniscal cartilage surfaces, whereas a collagen scaffold designed for osteoinduction failed to induce any integration of meniscus. In conclusion, the stem cell/collagen-scaffold implant is a potential therapeutic treatment for the repair of white zone meniscal cartilage tears.

Numerical Simulation of Two-dimensional Meniscus Surface and Its Application to Estimation of Wetting Behavior between Solid Substrate and Melt

Numerical Simulation of Two-dimensional Meniscus Surface and Its Application to Estimation of Wetting Behavior between Solid Substrate and Melt

Transport and retention of colloidal particles in partially saturated porous media: Effect of ionic strength

We directly observed pore‐scale attachment of fluorescent synthetic polystyrene colloids (1.0 μm diameter) in a partially saturated sand pack (pore space saturation ranging from 0.7 to 0.9) at four solution ionic strengths (0, 1, 100, 200 mmol NaCl). Sequential confocal laser microscope images were analyzed to quantify colloid retention, particularly at air‐water meniscus‐solid (AWmS) interfaces. We concurrently measured effluent colloid concentrations to determine overall matrix retention. Ionic strength had no effect on meniscus contact angles (26.7 ± 3.7 degrees) or surface tension (63–67 mN/m), both important components of the capillary forces thought to play the primary role in retention at the AWmS interfaces. AWmS interfaces attachment was greatest at 1 mmol, with the 0 mmol ionic strength reducing attachment by half. Increasing ionic strength to 100 and 200 mmol markedly decreased colloid retention at the AWmS interfaces due to observed increased competing attachment at grain surfaces (solid/water interface) that reduced the number of colloids available for AWmS interface attachment.

Mechanical injury of explants from the articulating surface of the inner meniscus

Knee osteoarthritis is accelerated by damage to the meniscus, a fibrocartilage tissue that assists in load transmission. However, little is known about the mechanical or cellular response of the meniscus to injurious overloading. Here, in vitro studies explored injury to meniscal explants using a compressive overloading protocol that has been well characterized for articular cartilage. Cartilage samples were processed in parallel as a reference to the extensive literature on cartilage injury. Injured meniscal explants showed extensive cell death at the articulating surface but no gross tissue damage, while similar conditions of peak stress and strain resulted in cartilage surface fissures and cell death consistent with moderate overloading. Post-injury gene expression in meniscal explants indicated a decrease in seven of the nine catabolic and pro-inflammatory molecules surveyed, while cartilage experienced a downregulation in ADAMTS-5 and TNF-α only. These data demonstrated a resiliency of the meniscus to injury, and that an acute increase in catabolic activities is not necessarily a consequence of mechanical overloading.