Radiology Case
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Radiographic findings: There
is a sub-chondral bone defect in the caudal aspect of the humeral head.
The arthrogram reveals a small amount of contrast material superimposed
in a linear fashion to the caudal aspect of the humeral head. The region
of the bicipital groove is within normal limits.
Radiographic impression: The findings are consistent with osteochondrosis dessicans of the humeral head.
Comments: Osteochondrosis is a defect in endochondral ossification where the articular columnated chondrocytes cells do not go on to hypertrophy and mineralize. This process leaves a flattened area of subchondral bone that can be appreciated radiographically. The cause of osteochondrosis is unknown. These lesions may be found incidentally in asymptotic patients and pain is not usually present until synovial fluid dissects through damaged cartilage to come in contact with the sub-chondral bone. This process is called osteochondrosis dessicans (OCD). The damaged cartilage may form a flap that may stay attached or may break off and become a joint mouse. Most commonly the flap will localize at the caudal aspect of the humeral head and occasionally the detached flap will deposit into the synovial sheath of the biceps tendon causing a bicipital tenosynovitis. Since the flap is cartilage it can not be seen radiographically and an arthrogram or MRI is necessary to identify it as in this case. Common anatomical locations for OCD in dogs include the caudal humeral head, the medial condyle of the humerus, the medial and lateral femoral condyles, and medial trochlear ridge of the talus. Less common locations include the medial coronoid process of the elbow, the trochlea of the femur, the lateral ridge of the talus, and the body of the first sacral vertebrae.1,2 Performing radiographs on the opposite shoulder is recommended, as this condition is very often bilateral.
The images are courtesy of Washington State University, College of Veterinary Medicine, Department of Radiology.
References
- Probst C, Johnston S. Osteochondrosis In: Slatter D, ed. Textbook of Small Animal Surgery. 2nd ed. Philadelphia: W.B. Saunders, 1993;1944-1966.
- Bennett D, May C. Joint Diseases of Dogs and Cats In: Ettinger SJ and Feldman EC, eds. Textbook of Veterinary Internal Medicine : Diseases of the Dog and Cat. 4th ed. Philadelphia: W.B. Saunders, 1995;2042-2046.
Dr. John Feleciano, DVM, DACVR
Dr. Renee Leveille, DVM, DACVR