Mechanical properties ofinstantly repaired articular cartilage defects by tissue engineering / 医用生物力学

ABSTRACT

Objective To investigate the mechanical properties of both artificial cartilage and host cartilage by establishing the in vitro model of tissue engineered cartilage for repairing defects. Methods The agarose gel as an artificial cartilage was implanted in a deep cartilage defect connected with biological adhesive to set up the in vitro model of tissue engineered articular cartilage defects. Under the compression load, the instant mechanical behavior of the repair area was studied using the digital image correlation technology. Results There was no cracking phenomenon occurred at the interface during the compression process. The Strain distributions at middle layer of the repair area were obtained when the cartilage thickness appeared changes with 3.5%, 5.6%, 7.04% and 9.0% by the compression, respectively. When the compressing change increased from 3.5% to 9%, the maximum compressive strain of host cartilage was increased by 75.9%, and the maximum tensile strain of artificial cartilage was increased by 226.99% in the vertical direction of cartilage surface. In the direction parallel with cartilage surface, the maximum tensile strain at the interface was increased by 116.9%, and the increment was far more than that at the host cartilage area and artificial cartilage area. For shear strain at the repair area, the direction of shear strain at the interface changed oppositely with the compression increasing. Conclusions The repair effect of tissue engineered cartilage was uncertain due to the mechanical environment of the repair area. After the tissue engineered cartilage was implanted in the defect, the repair area was under the influence of complex strain states. The strains changed greatly at the interface both with the host cartilage and artificial cartilage as the compression increasing. The strain in the vertical direction of cartilage surface at the interface might change from compressive stain to tensile strain, which was significantly increased in the direction parallel with cartilage surface. The strain direction at the interface could even be changed oppositely, and the shear strain appeared rapidly increase. The complex strain states lead to such great changes in mechanical environment of the defect area, and may cause cracking at the interface, and even further affect the repair process. Therefore, attention should be given to this complex mechanical environment during cartilage defect repair process in clinical treatment.