| Articular cartilage defects and degeneration are usually caused by arthritis or the athletic injuries. The bone can repair itself by regeneration but the cartilage can not. So, researchers tried various ways to repair or regenerate the cartilage. At present, tissue engineering as an ideal biological repair method is moving toward clinical. Theoretical and experimental studies indicated that the cartilage is very sensitive to mechanical stimulation. And suitable mechanical stimulation can promote growth and development, and maintain the structure and function of cartilage. But the mechanical state of cartilage during the repairing of defects by tissue engineering can not be obtained through the experiment or existing measuring means. This brings the result of the repairing greater uncertainty. Further more, the insufficiency of mechanical function of artificial cartilage cultured by tissue engineering has blocked the progress of clinical cartilage defects repairing.This thesis has conducted a more comprehensive research of stress-distribution rule after the repairing of cartilage defects by tissue engineering, based on the physiology structure and stress form of the knee joint cartilage, with the aid of finite element simulation technique and three-dimensional design tool of computer, integrating biology theory, engineering theory of tissue and organ cultured in vitro, materials mechanics, theoretical mechanics, mechanism and machine design. And it suggested for the first time the rolling compression load bioreactor for building functional cartilage. The speeds of rolling and compression in this bioreactor are adjustable. The main contents and results of this work, including:1. Start from the smallest stress unit of articular cartilage, we established a rolling compression load finite element model of cartilage defects repairing, through the simulation of the stress distribution of artificial and host cartilage by finite element software ABAQUS to explore the four factors'influence rules on the stress distribution. These factors includes artificial cartilage modulus, compression, load speed and defect size. Results indicated that the stress distribution significantly influenced by the elastic modulus of artificial cartilage and the amount of compression. Under usual load, different elastic modulus of artificial cartilage will cause big stress change of itself and the variation can achieve 2.47 times, while the variation of host cartilage is 4.31 times. Given elastic modulus 0.6Mpa of artificial cartilage for example, the stress of artificial cartilage and host cartilage under different load (compression from 5% to 30%) differs 3.26 times. The influence of load speeds and damage sizes are not obvious in this study, but they still have certain influence on the cartilage stress distribution.2. In view of the insufficiency of existing bioreactors, we designed a rolling compression load bioreactor to functionally culture cartilage in vitro. Its power is transported to a gearbox from a motor. Two output shafts of the gear box connect to two screw bodies respectively. Rolling load mechanism and sliding load mechanism were driven by the screw bodies respectively to achieve a rolling and sliding loads process. The speed ratio of rolling and compression loads is adjustable. It can also achieve simply of rolling or sliding loading process. The loading of the bioreactor to cartilage is close to the force applied to physical cartilage in knee joint. It provides a new mechanical condition for future construction of cartilage, and may cause a good exploration of building functional articular cartilage. |
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