Analysis of a Low-Invasive Method to Create Full-Thickness Articular Cartilage Defects in a Rat Model

[Purpose] We investigated a rat model of full-thickness articular cartilage defect without joint open surgery and histopathologically analyzed the time course of the tissue repair. [Subjects] A total of 40 male Wistar rats aged 9 weeks were used. [Method] Full-thickness defects of the articular cartilage were created over the capsule at the loading portion in the medial condyle of the femur. Ten rats each were randomly allocated to 4 groups, which were evaluated at 0, 4, 8 and 12 weeks after surgery. At the end of each period, knee joints were examined histopathologically. [Results] Full-thickness articular cartilage defects were created uniformly in our model. The defects were spontaneously resurfaced with hyaline-like tissue at 4 weeks postoperatively, but some articular cartilage remnants with aseptic necrosis and cloning of chondrocytes were found in the repair tissue. From 8 weeks to 12 weeks after surgery, the hyaline tissue was maintained, and the aseptic necrosis and cloning were observed in the partially repair tissue. [Conclusion] We have developed a rat model producing identically sized full-thickness defects of the articular cartilage.