There are many physical factors affecting the development of cartilage tissue,the mechanical con-dition is the main important one that particularly act.The mechanical conditions used in engineering cartilage tissue,such as compressive and shear force,fluid flow,hydrostatic pressure and tissue deformation or with some of them combined,were reviewed.From the standpoint of bionics,the mechanical environments ap-plied on tissue engineering should work in three aspects:providing adequately mechanical stimuli to the cells seeded in 3-D scaffold;ensuring the efficient mass-transport of the nutrients and waste products in the cells:promoting the development of functionally extracellular matrix in 3-D scaffold.The mechanical environments currently used only represented the part of mechanical conditions of in vive articular cartilage will be reviewed.In our view that rolling depression load may achieve the fit mechanical environment for cultivation of functional cartilage constructs in vitro.

There are many physical factors affecting the development of cartilage tissue,the mechanical con-dition is the main important one that particularly act.The mechanical conditions used in engineering cartilage tissue,such as compressive and shear force,fluid flow,hydrostatic pressure and tissue deformation or with some of them combined,were reviewed.From the standpoint of bionics,the mechanical environments ap-plied on tissue engineering should work in three aspects:providing adequately mechanical stimuli to the cells seeded in 3-D scaffold;ensuring the efficient mass-transport of the nutrients and waste products in the cells:promoting the development of functionally extracellular matrix in 3-D scaffold.The mechanical environments currently used only represented the part of mechanical conditions of in vive articular cartilage will be reviewed.In our view that rolling depression load may achieve the fit mechanical environment for cultivation of functional cartilage constructs in vitro.

Objective To study the damage propagation and evolution mechanism of cartilage under compressive loads.Methods The fiber-reinforced porous elastic model of cartilage with micro-defect was established by using finite element method,and the process of damage evolution under compressive loads was simulated and analyzed with parameters.The patterns of stress and strain distributions on cartilage matrix and collagen fiber at different damage extension stages were obtained.Results The strain in the surface and forefront of cartilage damage increased significantly with the increase of compression displacement,and they were obviously in positive correlation;in the process of damage evolution,there was a trend that cartilage extended to the deep and both sides simultaneously;cracks and damage in cartilage extended preferentially along the fiber tangent direction.With the aggravation of cartilage damage,the lateral extension speed was significantly faster than the longitudinal extension speed.Conclusions The process of cartilage damage extension has a close relationship with the distribution of fibers.The damages in matrix and fiber promote each other.The evolution speed and degree of cartilage vary constantly in different layers and at different stages.These results can provide the qualitative reference for prediction and repair of cartilage damage,as well as the theoretical basis for explaining pathological phenomena of damage degeneration and its clinic treatment.

Objective To analyze the stresses in implanted titanium solid and bone trabecular prosthesis hip replacements.Methods A femur model was built inversely based on Mimics software,and optimized using Geomagic software,and then materialized by SolidWorks software.The osteotomized femur was assembled with the metal femoral stem to form a model,and then the model was imported into ABAQUS for finite element calculation.The upper femur was divided into four regions in different states of integration:medial proximal point(small trochanter region),lateral proximal region(large trochanter region),proximal point of the femoral stem(region around the mid-portion of the styloid process)and distal region(around the end of the styloid process and distal portion).Calculations were carried out over the femoral stresses before and after implantation of titanium solid and trabecular prostheses under gait and stair-climbing loads and the interfacial stresses when the region was unintegrated.The type of deformation at the bone interface was analyzed by means of a stress ellipsoid.Results At the small trochanter region,the stress shielding rates of the trabecular prosthesis under gait and stair climbing loads were reduced by 20.5％and 14.7％compared to the titanium solid prosthesis,respectively.In case of different integration states of the titanium solid prosthesis,the interface tensile stresses under the gait and stair climbing loads were up to 10.842 MPa and 12.900 MPa,and the shear stresses reached 7.050 MPa and 6.805 MPa,respectively;in case of different integration states of the trabecular prosthesis,the interface tensile stresses under the gait and stair climbing loads were up to 3.858 MPa and 4.389 MPa,and the shear stresses reached 4.156 MPa and 3.854 MPa,respectively.Under the 2 different loads,the inboard shear stress ellipsoid of the interface opened toward the sides and the bone interface showed tensile deformation;the outboard shear stress ellipsoid of the interface opened up and down and had compressive deformation.Conclusion After total hip arthroplasty,the overall performance of the trabecular prosthesis is better than that of the titanium solid prosthesis.The unintegrated edges of the prosthesis-bone interface are susceptible to stress concentrations and distortion which may result in occurrence of failures.[Chinese Medical Equipment Journal,2024,45(3):29-35]

Objective To study the damage propagation and evolution mechanism of cartilage under compressive load. Methods The fiber-reinforced porous elastic model of cartilage with micro-defect was established by using finite element method, and the process of damage evolution under compressive load was simulated and analyzed with parameters. The patterns of stress and strain distributions on cartilage matrix and collagen fiber at different damage extension stage were obtained. Results The strain in surface and the forefront of cartilage damage increased significantly with the increase of compression displacement, and they were obviously in positive correlation; in the process of damage evolution, there was a trend that cartilage extended to the deep and both sides simultaneously; cracks and damage in cartilage extended preferentially along the fiber tangent direction. With the aggravation of cartilage damage, the lateral extension speed was significantly faster than the longitudinal extension speed. Conclusions The process of cartilage damage extension has a close relationship with the distribution of fibers. And the damage in matrix and fiber promote each other. The evolution speed and degree of cartilage vary constantly in different layers and at different stages. These results can provide the qualitative reference for prediction and repair of cartilage damage, as well as the theoretical basis for explaining clinical pathological phenomena of damage degeneration and treatment.