Poroelasticity And Layered Electrical Properties Of Articular Cartilage

Osteoarthritis(OA)is a complex disease with multiple factors which has become a major threat to human health.While the Pathogenesis of OA initiation and progression remain incompletely understood,it is well established that cartilaginous lesion is an important part of its process.Research has shown that changes in fluid flow behavior after cartilage defects may have functional consequences and then feedback to the development of the damage,resulting in progressive cartilage degeneration finally.And because the self-healing ability of damaged cartilage is very limited,artificial articular cartilage replacement and cartilage tissue engineering show a good application prospect in the field of articular cartilage repair.However,both artificial articular cartilage and cartilage tissue engineering scaffolds must meet certain shape and performance requirements to restore the normal function of cartilage.Therefore,the characterization of articular cartilage materials is an important prerequisite for the study of cartilage diseases and cartilage repair interventions.A considerable amount of research has been performed to date to investigate the depth-related mechanic properties of articular cartilage.However,these methods were based on full-thickness cartilage characterization,and cartilage in different regions may influence each other.Bioimpedance analysis,which is widely used in basic and clinical sciences,can detect minor changes in histology,but there is no work investigating the electrical impedance properties associated with cartilage depth.The mechanical and electrical properties related to the depth of articular cartilage remain to be further investigated.The main work and conclusions of this paper are as follows:(1)In this paper,a simplified porous elastic articular cartilage model was firstly established,and the analytical solutions of pore fluid pressure and velocity in an idealized cartilage damage model were obtained,and the influence of cartilage defect on interstitial fluid flow behavior was analyzed.The results showed that both the maximum pressure and the flow velocity of the defected cartilage were reduced compared to the normal cartilage.In addition,we also established a poroelastic model of human knee cartilage to study the effect of different cartilage surface defects on the internal pressure and flow velocity of the tissue to further explore the mechanism of cartilage degradation.In addition,since the permeability of articular cartilage increases and the elastic modulus decreases significantly during the degeneration process,the influence of permeability and elastic modulus were also discussed in this paper.The results showed that both interstitial fluid pressure and flow velocity decreased around articular cartilage defects compared to normal cartilage,and this trend was more severe with increasing defect radius or thickness.As the cartilage degeneration process took place,the increased fluid flow velocity caused severe nutrient loss,which may be the mechanism behind fluid involvement from cartilage defects to osteoarthritis.(2)In this paper,electrical impedance analysis,compression relaxation test and permeability test were performed on the superficial,middle and deep zones of articular cartilage,and the resistivity,phase angle,elastic modulus,relaxation time,and final relaxation rate of each zone of cartilage were obtained.The results showed that there were significant differences in mechanical and electrical properties of cartilage tissue in different zones in which resistivity,elastic modulus,relaxation time and final relaxation rate increased gradually from superficial zone to deep zone along the direction of cartilage thickness while the permeability decreased gradually.In this paper,theoretical mathematical modeling and finite element methods were used to study the interstitial fluid flow in the defect cartilage.In addition,we also explored the mechanical and electrical properties of porcine articular cartilage,aiming to provide data support for the treatment and diagnosis of clinical osteoarthritis and the research and application of filling and repairing materials.