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Altered knee joint mechanics in simple compression associated with early cartilage degeneration.

Dabiri Y, Li LP - Comput Math Methods Med (2013)

Bottom Line: As compared with a normal knee of the same compression, reduced fluid pressurization was observed in the degenerated knee.The results also indicated redistribution of stresses within the tissue and relocation of the loading between the tissue matrix and fluid pressure.These results may only be qualitatively interesting due to the small compression considered.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500 University Drive N.W., Calgary, AB, Canada T2N 1N4.

ABSTRACT
The progression of osteoarthritis can be accompanied by depth-dependent changes in the properties of articular cartilage. The objective of the present study was to determine the subsequent alteration in the fluid pressurization in the human knee using a three-dimensional computer model. Only a small compression in the femur-tibia direction was applied to avoid numerical difficulties. The material model for articular cartilages and menisci included fluid, fibrillar and nonfibrillar matrices as distinct constituents. The knee model consisted of distal femur, femoral cartilage, menisci, tibial cartilage, and proximal tibia. Cartilage degeneration was modeled in the high load-bearing region of the medial condyle of the femur with reduced fibrillar and nonfibrillar elastic properties and increased hydraulic permeability. Three case studies were implemented to simulate (1) the onset of cartilage degeneration from the superficial zone, (2) the progression of cartilage degeneration to the middle zone, and (3) the progression of cartilage degeneration to the deep zone. As compared with a normal knee of the same compression, reduced fluid pressurization was observed in the degenerated knee. Furthermore, faster reduction in fluid pressure was observed with the onset of cartilage degeneration in the superficial zone and progression to the middle zone, as compared to progression to the deep zone. On the other hand, cartilage degeneration in any zone would reduce the fluid pressure in all three zones. The shear strains at the cartilage-bone interface were increased when cartilage degeneration was eventually advanced to the deep zone. The present study revealed, at the joint level, altered fluid pressurization and strains with the depth-wise cartilage degeneration. The results also indicated redistribution of stresses within the tissue and relocation of the loading between the tissue matrix and fluid pressure. These results may only be qualitatively interesting due to the small compression considered.

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First principal strain at the normalized depth of 15/16 (deep layer) for the normal femoral cartilage and three cases of local cartilage degeneration as defined in Figure 2. This is an inferior view of the right knee; that is, the medial condyle is on the right.
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fig8: First principal strain at the normalized depth of 15/16 (deep layer) for the normal femoral cartilage and three cases of local cartilage degeneration as defined in Figure 2. This is an inferior view of the right knee; that is, the medial condyle is on the right.

Mentions: The distribution of normal strain along the tissue depth was also altered with degeneration in the medial condyle (Figure 7). This strain was associated with the lateral expansion of the tissue when compressed in the thickness direction. The strain was smaller in the superficial zone because more tangentially oriented fibers there restrained the lateral expansion. However, the first principal strain was actually higher in the superficial zone than in the middle and most deep zones due to high shear strains at the surface (not shown). The first principal strain in the deepest layer was the largest in Case 3 (Figure 8), mostly because of large shear strains at the cartilage-bone interface in Case 3 (the lateral strain shown in Figure 7 was not the largest at the deepest layer).


Altered knee joint mechanics in simple compression associated with early cartilage degeneration.

Dabiri Y, Li LP - Comput Math Methods Med (2013)

First principal strain at the normalized depth of 15/16 (deep layer) for the normal femoral cartilage and three cases of local cartilage degeneration as defined in Figure 2. This is an inferior view of the right knee; that is, the medial condyle is on the right.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3569885&req=5

fig8: First principal strain at the normalized depth of 15/16 (deep layer) for the normal femoral cartilage and three cases of local cartilage degeneration as defined in Figure 2. This is an inferior view of the right knee; that is, the medial condyle is on the right.
Mentions: The distribution of normal strain along the tissue depth was also altered with degeneration in the medial condyle (Figure 7). This strain was associated with the lateral expansion of the tissue when compressed in the thickness direction. The strain was smaller in the superficial zone because more tangentially oriented fibers there restrained the lateral expansion. However, the first principal strain was actually higher in the superficial zone than in the middle and most deep zones due to high shear strains at the surface (not shown). The first principal strain in the deepest layer was the largest in Case 3 (Figure 8), mostly because of large shear strains at the cartilage-bone interface in Case 3 (the lateral strain shown in Figure 7 was not the largest at the deepest layer).

Bottom Line: As compared with a normal knee of the same compression, reduced fluid pressurization was observed in the degenerated knee.The results also indicated redistribution of stresses within the tissue and relocation of the loading between the tissue matrix and fluid pressure.These results may only be qualitatively interesting due to the small compression considered.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500 University Drive N.W., Calgary, AB, Canada T2N 1N4.

ABSTRACT
The progression of osteoarthritis can be accompanied by depth-dependent changes in the properties of articular cartilage. The objective of the present study was to determine the subsequent alteration in the fluid pressurization in the human knee using a three-dimensional computer model. Only a small compression in the femur-tibia direction was applied to avoid numerical difficulties. The material model for articular cartilages and menisci included fluid, fibrillar and nonfibrillar matrices as distinct constituents. The knee model consisted of distal femur, femoral cartilage, menisci, tibial cartilage, and proximal tibia. Cartilage degeneration was modeled in the high load-bearing region of the medial condyle of the femur with reduced fibrillar and nonfibrillar elastic properties and increased hydraulic permeability. Three case studies were implemented to simulate (1) the onset of cartilage degeneration from the superficial zone, (2) the progression of cartilage degeneration to the middle zone, and (3) the progression of cartilage degeneration to the deep zone. As compared with a normal knee of the same compression, reduced fluid pressurization was observed in the degenerated knee. Furthermore, faster reduction in fluid pressure was observed with the onset of cartilage degeneration in the superficial zone and progression to the middle zone, as compared to progression to the deep zone. On the other hand, cartilage degeneration in any zone would reduce the fluid pressure in all three zones. The shear strains at the cartilage-bone interface were increased when cartilage degeneration was eventually advanced to the deep zone. The present study revealed, at the joint level, altered fluid pressurization and strains with the depth-wise cartilage degeneration. The results also indicated redistribution of stresses within the tissue and relocation of the loading between the tissue matrix and fluid pressure. These results may only be qualitatively interesting due to the small compression considered.

Show MeSH
Related in: MedlinePlus