Mechanical Behavior Analysis Of Tissue-engineering Repaired Cartilage Under Sliding Loads

The defects and degeneration of articular cartilages are common diseases in daily life.Because of the physical environment of articular cartilage without blood supply, it is verydifficult to achieve self-healing after the defects. Cartilage defects leads to patients with painduring the movement. Serious articular cartilage defects will lead to joint disability, and carryimmense suffering for the patients. Tissue engineering provides a new way for repairingarticular cartilage defects. But now there are many uncertainties of the repair effect in defectarea, it is closely related to mechanics performance and artificial cartilage characteristic in therepair area. Appropriate mechanical stimulation can promote the growth of cartilage tissue.But when applied too much load, the distribution of stress will be uneven in the restoredregion and the cartilage will suffer the secondary damage. Therefore, exploring the responseof cartilage repair area to the mechanical environment changes is very important.In this paper, it is based on the physiological structure of knee joint cartilage and slidingform of load, with the aid of finite element simulation software and digital image correlationtechnique, study on the mechanical properties of the cartilage repair area which underdifferent loading condition. The main contents and results are as follows:The repaired model of cartilage under sliding load is established with full-thicknessdefects. The host cartilage (natural cartilage) adopted the fiber-reinforced solid-liquid biphasicmodel. Layered structure is be used to reflect the elastic modulus of the cartilage changes withdepth; the permeability changing with the strain is obtained by nesting ABAQUS subprocedures and FORTRAN language; simulate the anti-tensile function of natural cartilage byadding the spring element at nodes of model. Artificial cartilage is simulated by homogeneousisotropic material, assuming that the artificial cartilage is bonded well with the host cartilage.It is investigated the effect of the amount of sliding speed, compression and modulus ofartificial cartilage on the stress, pore pressure, contact stress and Y direction strain of repairedregion when the slider moving to different positions. The results show that: the cartilage porepressure bore the main force under the dynamic loads. In the process of sliding, the positionof slider have great effect on the mechanical properties of the repair area and greater strainand stress appeared when the slider works in the joint face. The increased amount ofcompression increase the stress and deformation of the host and artificial cartilage, andespecially the deformation of joint face increased sharply, will cause cracking of cartilage.The increasing elastic modulus improves the carrying capacity of the artificial cartilage andappropriate modulus reduces the stress concentration on the joint. The increasing of slidingspeed reduces the amount of deformation, but will cause a greater impact on joints.It is studied by sliding loading experiment on the full-thickness defects of cartilage afterrepair, combining with the digital correlation technique to deal with the data of the image, and discussed the impacts which are caused by sliding compression and sliding speed on the straindistribution of repair areas. While changing the amount of sliding compression and the speed,some effects appear on the repairing areas. Through comparing strain values of different layer,it is found that the change in surface is the most obvious.The properties of cartilage in repair area are studied from experiment and simulation, itmakes the results more comprehensive and provides certain theoretical basis for preventionand treatment of clinical illness of articular cartilage.