Histomorphometric analysis of articular cartilage, zone of calcified cartilage, and subchondral bone plate in femoral heads from clinically normal dogs and dogs with moderate or severe osteoarthritis.
OBJECTIVE
To quantify and compare the microscopic changes in articular cartilage (AC), zone of calcified cartilage (ZCC), and subchondral bone plate in femoral heads from clinically normal dogs and dogs with moderate or severe osteoarthritis.


METHODS
Femoral heads from clinically normal dogs (n = 16) and dogs with moderate (24) or severe (14) osteoarthritis.


METHODS
Femoral heads were allocated to 3 categories (normal, moderate, or severe osteoarthritis) on the basis of radiographic findings, macroscopic findings, and histologic grade determined by use of a modified Mankin scale. Equally spaced 2-mm sections were cut in each femoral head in a coronal or transverse plane. Thickness of the AC, ZCC, and subchondral bone plate was recorded.


RESULTS
Mean thickness of AC was significantly greater in samples with moderate and severe osteoarthritis than those considered normal. Mean thickness of the ZCC was significantly greater in samples with moderate and severe osteoarthritis than those considered normal. Mean thickness of the subchondral bone plate in samples with severe osteoarthritis was significantly greater than those with moderate osteoarthritis and those considered normal. A significant decrease in AC thickness was detected in the proximomedial area of femoral heads with severe osteoarthritis, compared with those considered normal.


CONCLUSIONS
A cause and effect association between thickening of subchondral structures and thinning and loss of the overlying AC was not detected. Changes in AC were associated with changes in the subchondral bone plate, which is compatible with the theory of adaptation in response to altered load distribution.
Daubs
Brian M
BM
Comparative Orthopaedic Research Laboratory, Department of Medical and Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, USA.
Markel
Mark D
MD
Manley
Paul A
PA
D000818:Animals; D002358:Cartilage, Articular / Q000473:pathology*; D004283:Dog Diseases / Q000473:pathology*; D004285:Dogs; D006614:Hindlimb; D010003:Osteoarthritis / Q000473:pathology / Q000662:veterinary*