CARTILAGE CANALS IN EQUINE ARTICULAR EPIPHYSEAL GROWTH CARTILAGE AND A POSSIBLE ASSOCIATION WITH DYSCHONDROPLASIA/

Cartilage canals have been described in most mammals and contain the v ascular elements necessary for the maintenance of epiphyseal growth ca rtilage. The presence and longevity of cartilage canals in developing articular/epiphyseal cartilage of horses is described for the first ti me. Growth cartilages from 30 normal horses (from 130 days gestation t o age 2 years) and 6 cases of dyschondroplasia (age <15 months) were e xamined, Cartilage canals were located in the epiphyses of fetuses as early as 130 days gestation, The secondary centres of ossification had developed by 250 days gestation and, at full term (similar to 340 day s), the articular/epiphyseal cartilage was highly vascularised. Cartil age canals were closely surrounded by small round chondrocytes even wh en present in the zone of hypertrophic chondrocytes. From late gestati on until at least age 10 weeks, blood vessels surrounded by cartilage were found extending beyond the zone of hypertrophic chondrocytes into the secondary centre of ossification, Cartilage canals were absent fr om normal articular/epiphyseal cartilage of animals age >6 months. Car tilage canals were associated with retained cartilage of dyschondropla stic lesions found in animals age <15 months, The presence of cartilag e canals in association with dyschondroplastic lesions suggests they m ay have a role in the pathogenesis of this important disease.