Repair of the femoral head osteochondral defect in a swine model using autologous costal cartilage graft transplantation.

Background: Mosaic transplantation using autologous osteochondral graft (AOCG) is an effective treatment for osteochondral lesion however, at the sacrifice of irreversible damage to the donor articular surface. Costal cartilage is hyaline cartilage and has been utilized as a donor source in various surgeries. This study investigates the use of autologous costal cartilage graft (ACCG) for treating femoral head osteochondral defects in a swine model. Methods: Osteochondral defects were surgically induced in the femoral heads of one-year-old Bama pigs regardless of sex. The swine were divided into a Defect group without grafting (n = 6), a group grafted with ACCG (n = 6) and a group grafted with AOCG from ipsilateral trochlear groove (n = 6). Postoperatively, swine were allowed free cage activity without immobilization and were euthanized at either 3 or 6 months. Repair effects were evaluated using μCT, MRI, histology and immunohistochemistry (IHC) to assess the osteochondral properties of the grafted femoral head. Results: There was no difference in the hip function of the Bama pigs between AOCG and ACCG groups. The International Cartilage Repair Society (ICRS) scores showed no difference between AOCG and ACCG at both time points. ACCG exhibited comparable trabecular thickness as AOCG's, but lower trabecular number and higher trabecular separation. Percent bone volume was significantly lower in the ACCG group when compared to AOCG at 3 months, but not at 6 months. Modified MOCART scores were significantly higher in the AOCG group at 3 months but not at 6 months. MRI also detected increasing degree of ossification in the costal cartilage graft at all time points. Histologically, ACCG formed a subchondral bone interface while maintaining the hyaline cartilage characteristics on the articular surface. We also found that superficial layer of ACCG integrated more thoroughly with the recipient cartilage than AOCG did. Furthermore, histology and IHC collectively demonstrated that ACCG had undergone endochondral ossification process at the subchondral layer, evidenced by increased type I collagen expression and decreased type II collagen expression. No donor-site morbidity was noted with ACCG procedure during the study. Conclusions: This study demonstrates that ACCG can serve as a viable alternative to AOCG for treating femoral head osteochondral defects. The findings show that ACCG offers comparable outcomes to AOCG while avoiding the donor-site morbidity associated with AOCG. Given the challenges related to the donor tissue availability and associated complications in the clinical practice, ACCG could provide a promising and less invasive option for cartilage repair. The translational potential of this article: This proposed method can be translated into practical treatment for repairing osteochondral lesion in human hip joints and provide a new avenue for treating osteochondral lesions in large joints.