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Time-dependent behavior of cartilage surrounding a metal implant for full-thickness cartilage defects of various sizes: a finite element study
KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.ORCID iD: 0000-0002-5819-4544
2012 (English)In: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940, Vol. 11, no 5, 731-742 p.Article in journal (Refereed) Published
Abstract [en]

Recently, physiological and biomechanical studies on animal models with metal implants filling full-thickness cartilage defects have resulted in good clinical outcomes. The knowledge of the time-dependent macroscopic behavior of cartilage surrounding the metal implant is essential for understanding the joint function after treating such defects. We developed a model to investigate the in vivo time-dependent behavior of the tibiofemoral cartilages surrounding the metal implant, when the joint is subjected to an axial load for various defect sizes. Results show that time-dependent effects on cartilage behavior are significant, and can be simulated. These effects should be considered when evaluating the results from an implant. In particular, the depth into the cartilage where an implant is positioned and the mechanical sealing due to solidification of the poroelastic material need a time aspect. We found the maximal deformations, contact pressures and contact forces in the joint with time for the implant positioned in flush and sunk 0.3 mm into the cartilage. The latter position gives the better joint performance. The results after 60 s may be treated as the primary results, reflecting the effect of accumulation in the joint due to repeated short-time loadings. The wedge-shaped implant showed beneficial in providing mechanical sealing of cartilages surrounding the implant with time.

Place, publisher, year, edition, pages
2012. Vol. 11, no 5, 731-742 p.
Keyword [en]
Cartilage defects, Finite element modeling, Knee, Metal implant, Poroelastic, Sheep
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-26502DOI: 10.1007/s10237-011-0346-7ISI: 000303378200012Scopus ID: 2-s2.0-84861096730OAI: oai:DiVA.org:kth-26502DiVA: diva2:372424
Note
QC 20120628Available from: 2010-11-25 Created: 2010-11-25 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Finite Element Simulations of Biphasic Articular Cartilages With Localized Metal Implants
Open this publication in new window or tab >>Finite Element Simulations of Biphasic Articular Cartilages With Localized Metal Implants
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Articular cartilage is a specialized connective soft tissue that resides onthe ends of long-bones, transfers the load smoothly between the bones in diarthrodialjoints by providing almost frictionless, wear resistant sliding surfacesduring joint articulation. Focal chondral or osteochondral defects in articularcartilage are common and show limited capacity for biological repair. Furthermore,changes in the bio-mechanical forces at the defect site may makethe tissue more susceptible to continued degeneration. Alternatively, the contouredfocal resurfacing metal implant can be used to treat such full thicknesscartilage defects. Physiological and biomechanical studies on animal modelswith metal implant have shown good clinical outcomes. However, the mechanicalbehavior of cartilage surrounding the implant is not clearly known withrespect to the joint function after treating such defects with metal implantsand also to improve the implant design. We developed a simple 3-dimensionalfinite element model by approximating one of the condyles of the sheep kneejoint. Parametric study was conducted in the simulations to verify differentprofiles for the implant, positioning of the implant with respect to cartilagesurface, defect size and to show the mechanical sealing effect due to the wedgeshape of the implant. We found the maximal deformations, contact pressuresand stresses which constitute the mechanical behavior of cartilages. We alsoconfirmed that using a metal implant to fill the full thickness chondral defectsis more beneficial than to leave the defect untreated from mechanical point ofview. The implant should be positioned slightly sunk into the cartilage basedon the defect size, in order to avoid damage to the opposing surface. The largerthe defect size, the closer the implant should be to the flush. We also simulatedthe time dependent behavior of the cartilages. In all the simulations, a staticaxial loading was considered. The wedge shape of the implant provided themechanical sealing of the cartilage surrounding the implant. The determineddeformations in the cartilages immediately surrounding the implant are instrumentalin predicting the sticking-up of the implant into the joint cavity whichmay damage opposing soft tissues.

Place, publisher, year, edition, pages
Stockholm: Universitetsservice US-AB, 2010. viii, 49 p.
Series
Trita-MEK, ISSN 0348-467X ; 2010:10
Keyword
finite element analysis, articular cartilage defects, knee joint, metal implant, poroelastic, biphasic
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-26381 (URN)
Presentation
2010-12-16, E3, Osquare backe 14, Royal Institute of Technology, Stockholm, 10:15 (English)
Opponent
Supervisors
Note
QC 20101125Available from: 2010-11-25 Created: 2010-11-24 Last updated: 2010-12-03Bibliographically approved
2. Mechanics and Growth of Articular Cartilage Around a Localized Metal Implant
Open this publication in new window or tab >>Mechanics and Growth of Articular Cartilage Around a Localized Metal Implant
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Articular cartilage is a specialized connective soft tissue that resides on the ends of long-bones, and transfers the load smoothly between the bones in diarthrodial joints by providing almost frictionless, wear resistant sliding surfaces during joint articulation. Focal chondral or osteochondral defects in articular cartilage are common and show limited capacity for biological repair. Furthermore, changes in the bio-mechanical forces at the defect site may make the tissue more susceptible to continued degeneration. Alternatively, a contoured focal resurfacing metal implant can be used to treat such full-thickness cartilage defects. Physiological and biomechanical studies on animal models with metal implant have shown good clinical outcomes. However, the mechanical behavior of cartilage surrounding the implant has remained largely unanswered with respect to the joint function.

First, we developed a simple 3-dimensional finite element model by approximating one of the condyles of a sheep knee joint and parametrically studied the effects of shape, size and positioning of the implant on the mechanical behavior of the cartilage surrounding the implant. The mechanical sealing effect due to the wedge shape of the implant was studied. We also simulated the time dependent behavior of the cartilage surrounding the implant. In the second part, we developed a more sophisticated model accounting for biological growth aspects of the cartilage around the implant together with the in vivo mechanical response of the cartilage in an intact human knee joint. An axisymmetric representation of a human knee condyle including both cartilage layers, meniscus and tibia was considered. A cartilage growth finite element model incorporating dynamic loading from walking, which drives the growth stimulation in the cartilage, was developed. Two individually growing constituents in the solid matrix of cartilage together with the biphasic contacts in the joint were considered in the growth model. From our simulations it is evident that the cartilage near the implant was more stimstimulated, whence the defect edge of the cartilage was growing onto the implant.

The models developed in the present work are simulation tools and have a potential, in relevant aspects, to predict the physiological behavior of the cartilage surrounding the metal implant.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. x, 48 p.
Series
Trita-MEK, ISSN 0348-467X ; 2013:08
Keyword
finite element analysis, articular cartilage defects, growth, knee, focal knee resurfacing, metal implant, poroelastic, porohyperelastic, biphasic
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-121573 (URN)978-91-7501-720-4 (ISBN)
Public defence
2013-05-22, F3, Lindstedtsvägen 26, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20130502

Available from: 2013-05-02 Created: 2013-05-02 Last updated: 2013-05-08Bibliographically approved

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