Longitudinal Cannon-Bone Fracture and Su bchond ral Osteoscierosis in the Racehorse An Examination of the Cannon-Bones of Two Cases with the Fracture- Mikihiro KANEKO,* Keiji KIRYU,* Masa-aki OIKAWA,* Takumi KANEMARU,* Takeshi YAMAMOTO,** and Hiroshi SAToH*** In 2 racehorses spontaneously affected with longitudinal fracture of the cannon bone, each of the distal articular portions of both third metacarpus (four Mc V) and metatarsus these portions of Mc V and Mt V, there existed focal lesions consisting of cartilage concave and ulcer on the articular surface, and osteosclerosis and osteosis in the subchon doral cancellous bone. The fracture line of the cannon bone appeared to run through such focal lesion in both animals.
Fig. 3. Distal end of right third metatarsal bone (Mt V) with longitudinal fracture Frontal section (3mm thick) shows a fracture line similar to one of Fig. 1. Case No, 2. Fig. 4. Radiogram of Fig. 3
Fig. 5 Distal end of right Mc V without fracture Frontal section (3mm thick) shows a concave and ulcer (arrow) of articular cartilage surrounded by osteosclerotic bone tissue (double arrow). Case No. 2. Fig. 6. Radiogram of sagittal section (3mm thick) of distal end of right Mc V It shows a focal lesion with fissure formation in the tissue beneath articular cartilage. Case No. 1.
Fig. 7. Subchondral osteosclerosis of distal end of right Mt V The structure of substantia spongiosa looks like that of substantia compacta. Case No. 1. Hematoxylin and eosin (HE) staining, ~21.5 Fig. 8. Area corresponding to the focal lesion in Fig. 5 The lesion reveals clefts in articular cartilage and subchondral bone tissue. The cartilage is proliferative and degenerative. The substantia spongiosa surrounding clefts is affected with osteosis and osteosclerosis, Case No. 1. HE staining, ~20.7.
Fig. 9. Area corresponding to the focal lesion in Fig. 6 Fissure, including debris, is surrounded by osteosclerotic tissue. Case No, 1, HE staining, ~20.7. Fig. 10. Area corresponding to the fracture line in Fig. I Although the fracture line is fresh, the changes of osteosclerosis and osteosis seem to be along the fracture line, Case No. 1. HE staining, ~20.7.
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