Abstract
Articular cartilage constituents (collagen, proteoglycans, fluid) are significantly altered during osteoarthritis (OA). A fibril-reinforced poroelastic (FRPE) material model can separate the contribution of each constituent on the mechanical response of cartilage. Yet, these properties and their OA related alterations are not known for human tibial cartilage. To answer this gap in the knowledge, we characterized the FRPE as well as elastic and viscoelastic properties of healthy and osteoarthritic human tibial cartilage. Tibial osteochondral explants (n = 27) harvested from 7 cadavers were mechanically tested in indentation followed by a quantification of elastic, viscoelastic and FRPE properties. Then they were histopathologically OARSI graded for the severity of OA. FRPE modeling revealed that non-fibrillar matrix modulus was higher in the healthy group compared to the early OA (p = 0.003) and advanced OA (p < 0.001) groups. The initial fibril network modulus was also higher in the healthy group compared to the early OA (p = 0.009) and advanced OA (p < 0.001) groups. The permeability correlated with the OARSI grade (p = 0.002, r = 0.56). For the first time, the FRPE properties were characterized for human tibial cartilage. This knowledge is crucial to improve the accuracy of computational knee joint models.
Highlights
Articular cartilage, covering the endplates of the articulating bones, provides smooth movements in human joints
Healthy and osteoarthritic human tibial cartilage were characterized by combining indentation testing, tissue-level FE modeling and histological Osteoarthritis Research Society International (OARSI) grading for determining the severity of OA in the samples
Cartilage was modeled by applying the fibril-reinforced poroelastic (FRPE) material model, which enables the evaluation of the contribution of the cartilage constituents (PGs, collagen, fluid) on the mechanical response of the tissue
Summary
Articular cartilage, covering the endplates of the articulating bones, provides smooth movements in human joints. The main constituents contributing to the mechanical function of cartilage are negatively charged proteoglycans (PGs), collagen fiber network and interstitial fluid.[31]. Osteoarthritis (OA) is a degenerative joint disease in which all these constituents experience substantial changes resulting in an altered mechanical function of the cartilage tissue. During OA development, especially the superficial zone of cartilage experiences drastic changes, such as fibrillation of the collagen fiber network together with decreased PG and collagen contents and increased interstitial fluid content.[5,19,20,39] These changes result in a decrease in the equilibrium and dynamic moduli as well as an increase in tissue permeability, which will reduce the loadbearing capacity of cartilage
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