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J Biomech. 2017 Aug 16;61:34-44. doi: 10.1016/j.jbiomech.2017.06.041. Epub 2017 Jul 6.

The effect of fixed charge density and cartilage swelling on mechanics of knee joint cartilage during simulated gait.

Author information

1
Department of Applied Physics, University of Eastern Finland, Kuopio, Finland; Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland. Electronic address: lasse.rasanen@uef.fi.
2
Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
3
Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland; High Field MR Center, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria.
4
Orthopaedic Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands.
5
High Field MR Center, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria; CD Laboratory for Clinical Molecular MR Imaging, Vienna, Austria.
6
Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland; Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland; Medical Research Center, University of Oulu and Oulu University Hospital, Oulu, Finland.
7
Department of Applied Physics, University of Eastern Finland, Kuopio, Finland; Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland.

Abstract

The effect of swelling of articular cartilage, caused by the fixed charge density (FCD) of proteoglycans, has not been demonstrated on knee joint mechanics during simulated walking before. In this study, the influence of the depth-wise variation of FCD was investigated on the internal collagen fibril strains and the mechanical response of the knee joint cartilage during gait using finite element (FE) analysis. The FCD distribution of tibial cartilage was implemented from sodium (23Na) MRI into a 3-D FE-model of the knee joint ("Healthy model"). For comparison, models with decreased FCD values were created according to the decrease in FCD associated with the progression of osteoarthritis (OA) ("Early OA" and "Advanced OA" models). In addition, a model without FCD was created ("No FCD" model). The effect of FCD was studied with five different collagen fibril network moduli of cartilage. Using the reference fibril network moduli, the decrease in FCD from "Healthy model" to "Early OA" and "Advanced OA" models resulted in increased axial strains (by +2 and +6%) and decreased fibril strains (by -3 and -13%) throughout the stance, respectively, calculated as mean values through cartilage depth in the tibiofemoral contact regions. Correspondingly, compared to the "Healthy model", the removal of the FCD altogether in "NoFCD model" resulted in increased mean axial strains by +16% and decreased mean fibril strains by -24%. This effect was amplified as the fibril network moduli were decreased by 80% from the reference. Then mean axial strains increased by +6, +19 and +49% and mean fibril strains decreased by -9, -20 and -32%, respectively. Our results suggest that the FCD in articular cartilage has influence on cartilage responses in the knee during walking. Furthermore, the FCD is suggested to have larger impact on cartilage function as the collagen network degenerates e.g. in OA.

KEYWORDS:

Articular cartilage; Finite element analysis; Fixed charge density; Gait; Knee joint; Proteoglycans; Swelling

PMID:
28807526
DOI:
10.1016/j.jbiomech.2017.06.041
[Indexed for MEDLINE]

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