The role of osteonecrosis in canine coronoid dysplasia: Arthroscopic and histopathological findings

Coronoid dysplasia (CD) or medial coronoid disease is part of canine elbowdysplasia and eventually results
in osteoarthrosis. Although CDwas originally attributed to disturbed endochondral ossification,more recent
data point to the subchondral bone. The objective of this study was to assess dysplastic bone and cartilage
of dogs that underwent unilateral or bilateral arthroscopic subtotal coronoidectomy for the treatment
of CD. Arthroscopic findings and histopathology of bone and cartilage removed from elbow joints
with CD were compared.
The most common arthroscopic finding was fragmentation with softening of the subchondral bone
of the central part of the medial coronoid process. In dogs without obvious fragmentation, CD was
characterised by bone softening and chondromalacia. During arthroscopic intervention dysplastic bone
and cartilage were collected for histopathological assessment. Forty-five slices of formalin-fixed, paraffinembedded
bone and cartilage samples were stained using haematoxylin and eosin and evaluated. Histopathological
findings primarily consisted of osteonecrosis of subchondral bone with necrosis within
the marrow spaces. Histopathological changes in the articular cartilage were characterised by fibrillation,
chondrocyte clone formation, and focal cartilage necrosis. The pathology was found primarily in the
subchondral bone and not in the articular cartilage. Vascular compromise may play a role in the pathogenesis
of osteonecrosis in CD.