Experimental osteochondritis dissecans--the role of cartilage canals in chondral fractures of young rabbits.

Skeletal immature rabbits were used to study the pathogenesis of Osteochondritis Dissecans (OCD). Both histological studies and a radiographical examination were utilized after sagittal and coronal surgical chondral fractures were made in the femoral condyles cartilage. Serial microangiographies were performed in rabbits between 0 and 84 days after the chondral fractures were made. Analyses of the histology and microradiography findings suggest in either a coronal or sagittal direction, that avascular lesions like an experimental OCD occur as a sequence of chondral injury. A fracture in a wide pedicle of a stable cartilaginous flap with abundant cartilage canals heals in the usual way. However, a fracture in an unstable fragment with a small isthmus devoid of cartilage canals and of nutritious vessels, probably doesn't heal completely and a fragment closely resembling OCD is instead formed. An experimental OCD depends on the slender hinge of the flap and on the lack of stability in a rabbit's non-ossified epiphyseal cartilage. The damage to the cartilage canals and the rupture of vessels in the canals by a chondral fracture and the disturbance in the revascularization in the healing process by abnormal mechanical forces are thus most likely considered to be the main factor for OCD production.