The Study For The Mass Transfer Of Articular Cartilage Under Rolling Depression Loading

Articular cartilage plays important roles in bearing mechanical loading and absorbingthestress wave of dynamic loading conditions and lubricating joints，it is the area that someChronic illnesses are produced minutely. It is said that the healthy mass transfer of Articularcartilage is one key piont over come the lesion and rebuilding successful in cartilaginoustissue. In avascular adult articular cartilage, chondrocytes depend upon transport processesthrough the matrix for many biological activities including nutrient acquisition, wasterejection, cell signalling via cytokines and growth factors, deposition of newly synthesizedmatrix macromolecules, and enzyme-mediated matrix turnover. Mechanical condition drivesthe cartilage to obtain nutrition and exclude waste during daily activities. The investigation ofthe transport behavior within the tissue is important to the understanding of the mechanismsof nutritional transport and mechanosignal transduction in cartilage. Past studies on cartilagein vivo are mainly concentrated in the compression, we firstly put forward a new loadingapproach to study the process of cartilage mass transfer in this thesis. In our study, theapproach is called rolling and compression. Under the enviroment cased by rolling andcompression investigation of the transport behavior and physical signals within the tissue andis important to the understanding of the mechanisms of nutritional transport andmechano-signal transduction in cartilage.According to similarly studies in common experiment, in different mass transfermechanism in other form and based on the mechanism structure of articular cartilage, rollingload is considered as a typical representative to simulate the mechanical environment. Firstly,preliminary tests were setted up in vitro, we evaluate the metabolism of cartilage cell underthe rolling load; then in order to put the above tests into practice, we are going to study moreknowledge of mass transfer, the properly model is created in theory; in silico, a mixed finiteelement formulation was adopted to solve these 2D initial- and boundary-value problemsusing ANSYS software, the problem was solved using an iterative procedure in thecommercial finite element software. The most contents and results of this thesis including:1、experiment. the rhodamine、FITC- dextrans、TRITC-dextrans were choosed as thefluorescent tracer .The experimental group develope respectively in a roll controllingsubsystem and a compressive subsystem, and the control group keep doing nothing；thecompression rate of rolling loading is about 20%, rolling speed is 10cm / s, with experimentaltime respectively are differently. the cartilage is frozen and cut into slices, under thefluorescence microscopy we observe the slices and the intensity of fluorescence. Comparedwith the control group, the results show that the rolling load promoted the solute transportwithin articular cartilage.2、Mass transfer mathematical model. The purpose of this study was to implement thetriphasic theory into a commercially available finite element software package. In order to solve the mass transfer using ANSYS, the triphasic model was converted into athermo-mechanical interaction problem with convective heat transfer.3、Computer simulation. Start from the smallest stress unit of articular cartilage, weestablished a multi-layer structure rolling compression load finite element model of cartilagemass transfer, through the simulation of the concentration distribution of artificial by finiteelement software ANSYS to explore mass transfer influence process of cartilage in a differentamount of compression and load factor rate . The results show that the concentration field ofcartilage in rolling environment, improve compare with the steady-state in some way . Alongwith the increase of the compression rate and rolling speed, the temperature of each unit of thecartilage tissue has increased relative to the steady temperature relative to the steadytemperature and the Maximum growth occur in the right underneath of roller. Maximumstress and strain occurr near in the first layer.