Numerical Study on Mechanical Behavior of Tissue-Engineering Repaired Cartilage in Sliding Load Condition

2013 ◽  
Vol 441 ◽  
pp. 598-601
Author(s):  
Yu Zhou ◽  
Hai Ying Liu ◽  
Yu Tao Men ◽  
Li Lan Gao ◽  
Bao Shan Xu ◽  
...  
Keyword(s):  
Numerical Study ◽  
Compressive Strain ◽  
Load Condition ◽  
Repair Process ◽  
Cartilage Defects ◽  
Biphasic Model ◽  
Artificial Cartilage ◽  
Repairing Effect ◽  
Intensity Of Exercise ◽  
Engineered Cartilage

Mechanical state has a major impact on the repairing effect of tissue-engineered cartilage. The unusual state could result in the degeneration of artificial and host cartilage. A repaired cartilage defects was simulated by finite element simulation based on fiber-reinforced biphasic model in sliding load condition. The results showed that in the surrounding area of defects Mises stress, compressive strain and pore pressure are affected by the amount of compression and modulus of materials. Inadequate modulus leads to the declining mechanical bearing ability in defected position, while excessive modulus leads to increasing difference between the pressure on the two sides of bonding surface between artificial cartilage and host cartilage. During the repair process, it is suggested to choose the artificial cartilage modulus with both reasonable bearing ability and less stress concentration should be considered, and the intensity of exercise should also decrease to reduce the amount of compression.

Alternative Compressive Strain Capacity Performance Limits for Strain Based Design Applications

2016 ◽  
Author(s):  
Shawn Kenny ◽  
Robin Gordon ◽  
Greg Swank
Keyword(s):  
Structural Engineering ◽  
Negative Impact ◽  
Numerical Study ◽  
Compressive Strain ◽  
Elastic Stability ◽  
Ground Movement ◽  
Performance Limits ◽  
Strain Capacity ◽  
Industry Standards ◽  
Limiting Condition

Existing industry standards have established the compressive strain capacity of pipelines within an empirical basis. The compressive strain capacity is generally associated with the peak moment. This approach has evolved from elastic stability concepts used in structural engineering for unrestrained pipe segments subject to primary loading (i.e. force or load control) conditions. This limiting condition does not take advantage of the observed performance for buried pipelines, when subjected to displacement control events such as differential ground movement, where the pipe curvature can exceed the peak moment response without loss of pressure containment integrity. This inherent conservatism may have a negative impact on project economics or sanction where the compressive strain capacity, rather than tensile rupture limits, governs the strain based design methodology. For these conditions, alternative performance limits defining the pipe compressive strain capacity are required. A numerical study was conducted, using finite element methods, to examine possible alternative compressive strain criteria for use in strain-based design applications. The results from this study and the requirements to bring these concepts forward through integration with industry recommended practice are presented.

scholarly journals Numerical Study of Lymph Mechanics

2021 ◽  
Author(s):  
◽  
Daniel J. Watson
Keyword(s):  
Lymphatic System ◽  
Numerical Study ◽  
Patient Specific ◽  
Single Subject ◽  
3D Analysis ◽  
Large Network ◽  
Lumped Model ◽  
Biphasic Model ◽  
Lymphatic Valve ◽  
Scale Modelling

Methods taken from engineering and computer science were applied to the lymphatic system. Starting with a 3D analysis of a single subject-specific lymphatic valve. A mechanism was presented to explain previous experimental results showing the effect of trans-mural pressure on the pressure required to close lymphatic valves. The impor-tance of wall motion in future FSI studies of lymphatic valve dynamics were identified. Previous approaches to lumped modelling of the lymphatic system were considered and modifications were proposed. A less-idealised valve model, incorporating trans-mural dependent bias, was proposed as well as a method of allowing self-organised contrac-tion through a stretch-dependent frequency of contraction. A network of the superficial lymphatics of the upper-limb was reconstructed from an anatomical sketch. The net-work was used in conjunction with the lumped model to produce a 421 vessel lymphatic model consisting of 17,706 lymphangions. Several issues which impede large network scale modelling of the lymphatic system are identified. A simplified patient-specific biphasic model of lymphoedema was proposed and used to develop a novel shape-based metric for lymphoedema. A statistically significant relationship between the metric and the presence of lymphoedema was found.

scholarly journals Engineered cartilage tissue from biodegradable Poly(ε-caprolactone) scaffold and human umbilical cord derived mesenchymal stem cells

2018 ◽  
Vol 5 (02) ◽  
pp. 2000-2012
Author(s):  
Phuc Dang-Ngoc Nguyen ◽  
Ngoc Bich Vu ◽  
Ha Thi-Ngan Le ◽  
Thuy Thi-Thanh Dao ◽  
Long Xuan Gia ◽  
...  
Keyword(s):  
Stem Cells ◽  
Mesenchymal Stem Cells ◽  
Umbilical Cord ◽  
Alcian Blue ◽  
Cartilage Tissue ◽  
Cartilage Defects ◽  
Human Umbilical Cord ◽  
Biodegradable Poly ◽  
Safranin O ◽  
Engineered Cartilage

Introduction: Cartilage injury is the most common injury among orthopedic diseases. The predominant treatment for this condition is cartilage transplantation. Therefore, production of cartilage for treatment is an important strategy in regenerative medicine of cartilage to provide surgeons with an additional option for treatment of cartilage defects. This study aimed to produce in vitro engineered cartilage tissue by culturing and differentiating umbilical cord derived mesenchymal stem cells on biodegradable Poly(ε-caprolactone) (PCL) scaffold. Methods: Human umbilical cord derived mesenchymal stem cells (UCMSCs) were isolated and expanded according to previous published protocols. UCMSCs were labeled with CD90 APC‑conjugated monoclonal antibody (CD90-APC) and then seeded onto porous PCL scaffolds. Cell adhesion and proliferation on PCL scaffolds were evaluated based on the strength/signal of APC, MTT assays, and scanning electron microscopy (SEM). The chondrogenic differentiation of UCMSCs on scaffolds was detected by Alcian Blue and Safranin O staining. Results: The results showed that UCMSCs successfully adhered, proliferated and differentiated into chondroblasts and chondrocytes on PCL scaffolds. The chondrocyte scaffolds were positive for some markers of cartilage, as indicated by Alcian Blue and Safranin O staining. Conclusion: In conclusion, this study showed successful production of cartilage tissues from UCMSCs on PCL scaffolds.

scholarly journals 3D Cartilage Regeneration With Certain Shape and Mechanical Strength Based on Engineered Cartilage Gel and Decalcified Bone Matrix

2021 ◽  
Vol 9 ◽  
Author(s):  
Zheng Ci ◽  
Ying Zhang ◽  
Yahui Wang ◽  
Gaoyang Wu ◽  
Mengjie Hou ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Bone Matrix ◽  
Cartilage Regeneration ◽  
Cartilage Tissue ◽  
Cartilage Defects ◽  
High Porosity ◽  
Good Biocompatibility ◽  
Engineered Cartilage ◽  
Decalcified Bone Matrix

Scaffold-free cartilage-sheet technology can stably regenerate high-quality cartilage tissue in vivo. However, uncontrolled shape maintenance and mechanical strength greatly hinder its clinical translation. Decalcified bone matrix (DBM) has high porosity, a suitable pore structure, and good biocompatibility, as well as controlled shape and mechanical strength. In this study, cartilage sheet was prepared into engineered cartilage gel (ECG) and combined with DBM to explore the feasibility of regenerating 3D cartilage with controlled shape and mechanical strength. The results indicated that ECG cultured in vitro for 3 days (3 d) and 15 days (15 d) showed good biocompatibility with DBM, and the ECG–DBM constructs successfully regenerated viable 3D cartilage with typical mature cartilage features in both nude mice and autologous goats. Additionally, the regenerated cartilage had comparable mechanical properties to native cartilage and maintained its original shape. To further determine the optimal seeding parameters for ECG, the 3 d ECG regenerated using human chondrocytes was diluted in different concentrations (1:3, 1:2, and 1:1) for seeding and in vivo implantation. The results showed that the regenerated cartilage in the 1:2 group exhibited better shape maintenance and homogeneity than the other groups. The current study established a novel mode of 3D cartilage regeneration based on the design concept of steel (DBM)-reinforced concrete (ECG) and successfully regenerated homogenous and mature 3D cartilage with controlled shape and mechanical strength, which hopefully provides an ideal cartilage graft for the repair of various cartilage defects.

scholarly journals In Vitro Generation of Cartilage-Carrier-Constructs on Hydroxylapatite Ceramics with Different Surface Structures

2008 ◽  
Vol 2 (1) ◽  
pp. 64-70 ◽  
Author(s):  
Katharina Wiegandt ◽  
Christiane Goepfert ◽  
Teresa Richter ◽  
Daniel Fritsch ◽  
Rolf Janßen ◽  
...  
Keyword(s):  
Surface Structure ◽  
Biochemical Properties ◽  
Surface Structures ◽  
Cartilage Defects ◽  
Commercial Grade ◽  
First Results ◽  
Hydroxylapatite Ceramics ◽  
Engineered Cartilage

Tissue engineering approaches for healing cartilage defects are partly limited by the inability to fix cartilage to bone during implantation. To overcome this problem, cartilage can be - already in vitro - generated on a ceramic carrier which serves as bone substitute. In this study, the influence of a hydroxylapatite carrier and its surface structure on the quality of tissue engineered cartilage was investigated. Application of the carrier reduced significantly biomechanical and biochemical properties of the generated tissue. In addition, slight changes in the quality of the formed matrix, in the adhesive strength between cartilage and biomaterial and in attachment and proliferation of a chondrocyte monolayer could be observed for commercial grade carriers, with respect to modified topographies obtained by smooth grinding/polishing. These first results demonstrated an influence of the carrier and its surface structure, but further research is needed for explaining the described effects and for optimization of cartilage-carrier-constructs.

Insulin and Ascorbate Have a Much Greater Influence Than Transferrin and Selenous Acid on the Growth of Engineered Cartilage in Chondrogenic Media

2012 ◽  
Author(s):  
Alexander D. Cigan ◽  
Robert J. Nims ◽  
Michael B. Albro ◽  
Sarah L. Breves ◽  
Clark T. Hung ◽  
...  
Keyword(s):  
Cell Types ◽  
Biochemical Properties ◽  
Direct Result ◽  
Cartilage Defects ◽  
Growth And Remodeling ◽  
Promising Alternative ◽  
Matrix Deposition ◽  
Selenous Acid ◽  
Engineered Cartilage ◽  
Modeling Growth

Tissue engineering of cartilage, which is a much sought-after approach for treatment of osteoarthritis and cartilage defects, requires appreciable culture time. Chemically defined chondrogenic media (CM) are commonly employed as they offer a promising alternative to serum-based media, and often include insulin, transferrin, and selenous acid (ITS) as well as ascorbate [1]. Concentrations of ITS constituents have been optimized based upon their ability to stimulate proliferation of a variety of cell types [2]. However, little is reflected in the literature as to the influences of various ITS constituent concentrations upon cartilage matrix deposition by chondrocytes. In engineered cartilage constructs that seek to match compositional and mechanical properties of native cartilage, knowledge of such influences would be highly desirable, especially when optimizing nutrient, hormone and vitamin supply for large constructs wherein rates of transport and consumption become more critical. Furthermore, this information would prove useful in modeling growth and remodeling of engineered tissues. Therefore, this study seeks to elucidate mechanical and biochemical properties as a direct result of modulating ITS and ascorbate concentrations within chondrocyte-agarose constructs.

Micro-structure and Lagrangian statistics of the scalar field with a mean gradient in isotropic turbulence

2003 ◽  
Vol 474 ◽  
pp. 193-225 ◽  
Author(s):  
G. BRETHOUWER ◽  
J. C. R. HUNT ◽  
F. T. M. NIEUWSTADT
Keyword(s):  
Scalar Field ◽  
Isotropic Turbulence ◽  
Numerical Study ◽  
Compressive Strain ◽  
Scalar Fields ◽  
Scalar Dissipation ◽  
Small Scale ◽  
Length Scale ◽  
Random Forcing ◽  
Kolmogorov Length Scale

This paper presents an analysis and numerical study of the relations between the small-scale velocity and scalar fields in fully developed isotropic turbulence with random forcing of the large scales and with an imposed constant mean scalar gradient. Simulations have been performed for a range of Reynolds numbers from Reλ = 22 to 130 and Schmidt numbers from Sc = 1/25 to 144.The simulations show that for all values of Sc [ges ] 0.1 steep scalar gradients are concentrated in intermittently distributed sheet-like structures with a thickness approximately equal to the Batchelor length scale η/Sc½ with η the Kolmogorov length scale. We observe that these sheets or cliffs are preferentially aligned perpendicular to the direction of the mean scalar gradient. Due to this preferential orientation of the cliffs the small-scale scalar field is anisotropic and this is an example of direct coupling between the large- and small-scale fluctuations in a turbulent field. The numerical simulations also show that the steep cliffs are formed by straining motions that compress the scalar field along the imposed mean scalar gradient in a very short time period, proportional to the Kolmogorov time scale. This is valid for the whole range of Sc. The generation of these concentration gradients is amplified by rotation of the scalar gradient in the direction of compressive strain. The combination of high strain rate and the alignment results in a large increase of the scalar gradient and therefore in a large scalar dissipation rate.These results of our numerical study are discussed in the context of experimental results (Warhaft 2000) and kinematic simulations (Holzer & Siggia 1994). The theoretical arguments developed here follow from earlier work of Batchelor & Townsend (1956), Betchov (1956) and Dresselhaus & Tabor (1991).

Functional Tissue Engineering of Articular Cartilage Through Dynamic Loading of Chondrocyte-Seeded Agarose Gels

2000 ◽  
Vol 122 (3) ◽  
pp. 252-260 ◽  
Author(s):  
Robert L. Mauck ◽  
Michael A. Soltz ◽  
Christopher C. B. Wang ◽  
Dennis D. Wong ◽  
Pen-Hsiu Grace Chao ◽  
...  
Keyword(s):  
Articular Cartilage ◽  
Compressive Strain ◽  
Fold Increase ◽  
Physiological Strain ◽  
Equilibrium Modulus ◽  
Free Swelling ◽  
Dynamically Loaded ◽  
Engineered Tissue ◽  
Natural Tissue ◽  
Engineered Cartilage

Due to its avascular nature, articular cartilage exhibits a very limited capacity to regenerate and to repair. Although much of the tissue-engineered cartilage in existence has been successful in mimicking the morphological and biochemical appearance of hyaline cartilage, it is generally mechanically inferior to the natural tissue. In this study, we tested the hypothesis that the application of dynamic deformational loading at physiological strain levels enhances chondrocyte matrix elaboration in cell-seeded agarose scaffolds to produce a more functional engineered tissue construct than in free swelling controls. A custom-designed bioreactor was used to load cell-seeded agarose disks dynamically in unconfined compression with a peak-to-peak compressive strain amplitude of 10 percent, at a frequency of 1 Hz, 3× (1 hour on, 1 hour off)/day, 5 days/week for 4 weeks. Results demonstrated that dynamically loaded disks yielded a sixfold increase in the equilibrium aggregate modulus over free swelling controls after 28 days of loading (100±16 kPa versus 15±8 kPa,p<0.0001). This represented a 21-fold increase over the equilibrium modulus of day 0 4.8±2.3 kPa. Sulfated glycosaminoglycan content and hydroxyproline content was also found to be greater in dynamically loaded disks compared to free swelling controls at day 21 (p<0.0001 and p=0.002, respectively). [S0148-0731(00)00703-2]

Experimental and numerical study on bearing failure of countersunk composite–composite and composite–steel joints

2016 ◽  
Vol 51 (22) ◽  
pp. 3211-3224 ◽  
Author(s):  
Baifeng Yang ◽  
Zhufeng Yue ◽  
Xiaoliang Geng ◽  
Xin Guan ◽  
Peiyan Wang
Keyword(s):  
Composite Laminates ◽  
Numerical Study ◽  
Three Dimensional ◽  
Load Condition ◽  
Experimental Results ◽  
Composite Joints ◽  
Bearing Failure ◽  
Three Dimensional Finite Element ◽  
Steel Joints ◽  
Composite Steel

Tensile experiments were conducted on composite–composite joints and composite–steel joints with countersunk bolts while three-dimensional finite element models using progressive damage method on composite were developed to simulate bearing failure of joints. Experimental results showed good repeatability and bearing damage showed obvious difference between the two kinds of joints. Solid elements were chosen to model all the parts and laminates were partitioned into actual number of plies in order to gain accurate stress distribution and damage profile in each ply. A 3D Hashin-type criteria and degradation rules were implemented using a user subroutine in ABAQUS. Numerical results had good agreement with experimental results considering clearance effects. Composite–steel joints showed better carrying capacity than composite–composite joints according to load–displacement curves and damage evolution processes. Delamination were more severe in composite–composite joints indicating that it is necessary to pay attention to designing composite laminates and structures under certain load condition.

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