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Finite element simulations of a focal knee resurfacing implant applied to localized cartilage defects in a sheep model
KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
Department of Orthopaedics, Karolinska University Hospital/Huddinge and Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Sweden.
KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.ORCID iD: 0000-0002-5819-4544
2011 (English)In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 44, no 5, 794-801 p.Article in journal (Refereed) Published
Abstract [en]

Articular resurfacing metal implants have recently been tested in animal models to treat full thickness localized articular cartilage defects, showing promising results. However, the mechanical behavior of cartilage surrounding the metal implant has not been studied yet as it is technically challenging to measure in vivo contact areas, pressures, stresses and deformations from the metal implant. Therefore, we implemented a detailed numerical finite element model by approximating one of the condyles of the sheep tibiofemoral joint and created a defect of specific size to accommodate the implant. Using this model, the mechanical behavior of the surrounding of metal implant was studied. The model showed that the metal implant plays a significant role in the force transmission. Two types of profiles were investigated for metal implant. An implant with a double-curved profile, i.e., a profile fully congruent with the articular surfaces in the knee, gives lower contact pressures and stresses at the rim of the defect than the implant with unicurved spherical profile. The implant should be placed at a certain distance into the cartilage to avoid damage to opposing biological surface. Too deep positions, however, lead to high shear stresses in the cartilage edges around the implant. Mechanical sealing was achieved with a wedge shape of the implant, also useful for biochemical sealing of cartilage edges at the defect.

Place, publisher, year, edition, pages
2011. Vol. 44, no 5, 794-801 p.
Keyword [en]
Articular cartilage, Implant, Finite element analysis, Poroelastic, Biphasic, Knee, Sheep
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-26394DOI: 10.1016/j.jbiomech.2010.12.026ISI: 000288925800002Scopus ID: 2-s2.0-79952034335OAI: oai:DiVA.org:kth-26394DiVA: diva2:372421
Note

QC 20120328. Updated from submitted to published. Previous title: "Finite element simulation of a focal knee resurfacing implant applied to localized cartilage defects in a sheep model"

Available 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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