[RELATIONSHIP BETWEEN SUBCHONDRAL BONE RECONSTRUCTION AND ARTICULAR CARTILAGE REGENERATION IN A RABBIT MODEL OF SPONTANEOUS OSTEOCHONDRAL REPAIR].

OBJECTIVE

To explore the relationship between subchondral bone reconstruction and articular cartilage regeneration in a rabbit model of spontaneous osteochondral repair.

METHODS

Twenty-four 6-month-old New Zealand white rabbits were included. The osteochondral defects (4 mm in diameter and 3 mm in depth) were created in the trochlear groove of the unilateral femur, which penetrated the subchondral bone without any treatment. The rabbits were sacrificed at 1, 4, 12, and 24 weeks. after operation, respectively. The specimens were obtained for macroscopic, histological, and immunohistochemical observations. According to the International Cartilage Repair Society (ICRS) histological scoring, the effect of cartilage repair was assessed. The histomorphometrical parameters of subchondral bone were analyzed by micro-CT scan and reconstruction, and the relationship between cartilage repair and the histomorphometrical parameters of the subchondral bone were also analyzed.

RESULTS

Osteochondral defects could be repaired spontaneously in rabbit model. With time, defect was gradually filled with repaired tissue, subchondral bone plate under the defect region gradually migrated upward. Bone mineral density, bone volume fraction, tissue mineralized density, trabecula number, and trabecula thickness were increased, while trabecula spacing was decreased. Significant difference was found in the other parameters between different time points (P < 0.05) except for trabecula thickness between at 4 and 12 weeks after operation (P > 0.05). Histological examination showed that fibrous repair was predominant with rare hyaline cartilage. With time, ICRS scores increased gradually, showing significant differences between other time points (P < 0.05) except for between at 4 and 12 weeks after operation (P > 0.05). Among the histomorphometrical parameters of subchondral bone, the trabecula spacing was negatively correlated with ICRS score (r = -0.584, P = 0.039), and the other histomorphometrical parameters were positively correlated with ICRS score (r = 0.680-0.891).

CONCLUSION

There is relevant correlation as well as independent process between cartilage regeneration and subchondral bone reconstruction in the rabbit model of spontaneous osteochondral repair, and fast subchondral bone remodeling may adversely affect articular cartilage repair.