Study On Mechanical Properties Of Articular Cartilage Based On Ultrasonic Testing And Nanoindentation Testing

Articular cartilage plays an important role in the motion of human joint,such as lubrication,load-bearing and load dispersion,at the same time,osteoarthritis is one of the main form of articular cartilage disease at present.Therefore,accurate evaluation of the mechanical properties of normal and pathological articular cartilage is of great significance for the preparation and treatment of articular cartilage.For the mechanical properties of articular cartilage,its elastic modulus is the most basic and important characteristic of articular cartilage tissue in bone joint motion.This paper is based on ultrasonic and nanoindentation detection technology,mainly to study the elastic modulus test of articular cartilage.This paper analyzes the layered structure and viscoelastic properties of articular cartilage,and constructs a layered mechanical model of articular cartilage considering tissue viscoelasticity.The model of ultrasonic propagation in articular cartilage is optimized based on the finite element analysis software,simulated the propagation process of ultrasound in articular cartilage close to the actual situation.Finally,taking pig tibia as the research object,based on ultrasonic and nanoindentation testing methods,the normal and diseased articular cartilage were tested separately,and the elastic modulus of normal and diseased articular cartilage under the two testing methods was obtained and compared.Base on the finite element analysis software,this paper establish a threedimensional simulation model of articular cartilage,which simulates the propagation process of ultrasonic waves in articular cartilage close to the real situation,and analyzes the ultrasonic echo signal in normal and diseased articular cartilage at 15 MHz,20MHz,and 25 MHz.The result shows that the ultrasonic at 25 MHz can effectively distinguish the different layers of articular cartilage.Based on the above,the structure of the ultrasonic probe in the three-dimensional simulation model has been optimized.And established a two-dimensional simulation optimization model which considering viscoelasticity and biological attenuation characteristics.The propagation process of ultrasonic wave in articular cartilage at 25 MHz frequency was simulated,which proved the feasibility of ultrasonic wave to detect the mechanical properties of different layers of articular cartilage.Based on ultrasonic testing,the elastic modulus of the superficial layer and transition layer of normal articular cartilage were2.664±0.037 MPa and 2.332±0.044MPa;the elastic modulus of the superficial layer and transition layer of diseased articular cartilage were 2.564±0.034 MPa and 2.116±0.049 MPa.Based on nanoindentation testing,the elastic modulus of the superficial layer and transition layer of normal articular cartilage were2.499±0.096 MPa and 2.290±0.116MPaa;the elastic modulus of the superficial layer and transition layer of diseased articular cartilage were 2.349±0.077 MPa and 2.021±0.128 MPa.The experimental results show that,compared with normal articular cartilage,the elastic modulus of the superficial layer and transition layer of the diseased articular cartilage is significantly reduced.The flow chart and elastic modulus obtained by ultrasonic and nano-indentation were analyzed and compared.The results show that ultrasonic has the advantages of high stability,high efficiency and no damage in the testing of articular cartilage.