Cartilage Canals

Transection of vessels in epiphyseal cartilage canals leads to osteochondrosis and osteochondrosis dissecans in the femoro-patellar joint of foals; a potential model of juvenile osteochondritis dissecans.

"Ten Norwegian Fjord Pony foals were operated at the age of 13-15 days. Two vessels supplying the epiphyseal growth cartilage of the lateral trochlear ridge of the left distal femur were transected in each foal. Follow-up examination was carried out from 1-49 days post-operatively and included plain radiography, macroscopic and histological examination.
Transection[transection refers to division in half] of blood vessels within epiphyseal cartilage canals resulted in necrosis of vessels and chondrocytes, i.e. ischaemic chondronecrosis, in foals. Areas of ischaemic chondronecrosis were associated with a focal delay in enchondral ossification (osteochondrosis) in foals examined 21 days or more after transection, and pathological cartilage fracture (osteochondrosis dissecans) in one foal examined 42 days after transection."

"In epiphyseal growth cartilage, cartilage canals are regularly distributed, blind-ending tubular spaces that are present during the early phases of growth . An arteriole, its capillary bed and one or more venules course into and out of the cartilage through a single canal, and therefore represent true end arteries (“glomeruli”) . When they are no longer needed, cartilage canals regress by a physiological process known as chondrification, during which vessels disappear and perivascular mesenchymal cells within the canal differentiate into chondrocytes to fill the canal lumen with cartilage. Cartilage canals are also incorporated into the advancing ossification front during growth, and in piglets and foals, it has been suggested that the vessels are particularly vulnerable to failure during the incorporation process"

"“Programmed” chondrification when cartilage canals are no longer needed occurs within regions with thin cartilage before regions with thick cartilage"