Evaluation of the repair process of cartilage defects of the equine third carpal bone with and without subchondral bone perforation

Abstract

SUMMARY To determine the effect of subchondral bone drilling (forage) on the cartilage repair process after injury has occurred, a cartilage defect (1 cm in diameter) was created on the radial facet of the proximal surface of each third carpal bone in 6 adult horses. In one of the third carpal bones (right or left thoracic limb) of each horse, a 1-cm cartilage defect was created, and 5 holes (1 mm in diameter and 10 mm deep) were drilled through the subchondral bone into the cancellous bone. In the other thoracic limb, an identical defect was created, but not drilled. Analyses of cell numbers and types in the synovia and the mucin precipitate quality were done before, at 1 week after, and 3 weeks after surgical manipulation was done and showed no significant difference between the joint environment of drilled carpi and those of nondrilled carpi. At 21 weeks after surgical manipulation was done, each joint was examined radiographically, macroscopically, and microscopically to compare the condition of the joints and the state of repair of the cartilage in each defect. The amount of surface of the defect covered by the dense fibrous and fibrocartilagenous repair tissue and the thickness of the repair tissue were significantly greater ( P < 0.05 and P < 0.01, respectively) in the drilled carpal bones. In addition, the attachment of the repair tissue to underlying chondro-osseous tissue was better in the drilled carpal bones. Fibrocartilage was resurfacing the drilled defects, whereas only fibrous tissue was present in the nondrilled defects. Drilling through the subchondral plate into the cancellous bone did not promote osteoarthritis, as determined in comparative examinations of drilled and nondrilled joints. It was concluded that drilling through the subchondral bone plate into the cancellous bone improves the healing of cartilage defects of the third carpal bones in horses and has no identifiable adverse effects on the joint.