Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.
Issue link: http://todaysveterinarypractice.epubxp.com/i/715668
tvpjournal.com | September/October 2016 | T O day' S Ve T erinary Prac T ice Ju V enile Or T h OP edic d i S ea S e in dO g S & c a TS Peer r eviewed 31 fragment retrieval but, in cases of larger fragments, pantarsal arthrodesis may be advocated. All dogs should be neutered given that the reported heritability of all forms of osteochondrosis ranges from 10% to 45%. 10 Prognosis When contemplating the prognosis for OC, it is prudent to consider that not all joints are equal. A joint that is relatively nonconstrained, such as the shoulder, has a greater tolerance for abnormalities in cartilage pathology, whereas a more highly constrained joint, such as the tarsus, has little tolerance and, thus, a worse prognosis. Medical management of shoulder OC can be successful unless the cartilage flap dislodges, becomes mineralized, and is trapped in a joint capsule recess or near the biceps tendon, where it may cause irritation and inflammation. After removal, the prognosis appears to be excellent, with minimal to no development of osteoarthritic changes. 13 Due to cartilage loss, joint incongruity, and secondary osteoarthritis, stifle OC is traditionally given a fair to poor prognosis; however, treatment with joint resurfacing techniques is promising and appears to provide a more favorable prognosis. 15 Treatment for OC of the elbow and hock will often result in improved lameness. However, osteoarthritis will develop/progress and lameness is usually evident after exercise. In severe cases of tarsal OC, the prognosis for maintaining a functional joint is poor. 12 Retained Cartilage Cores Overview Retained cartilage cores (RCC)—also known as retained endochondral cartilage cores—represent a failure of endochondral ossification that most commonly affects the distal ulnar physis. These lesions are characterized: • Histologically, by the retention of hypertrophic chondrocytes • Grossly, as cones of physial cartilage that project from the distal ulnar physis proximally into the distal metaphysis. 3,12,16 Several etiopathogeneses of RCC exist, with no single theory universally accepted. Some postulate that RCC may result from a chondrocyte abnormality, which prevents progression of endochondral ossification, 6,8 while others suggest that RCC is a physial manifestation of osteochondrosis. 3,12,16 Given that RCC occurs primarily in large, fast-growing dogs, nutritional contributions have also been suspected. 12 Signalment Large- and giant-breed dogs are most commonly affected. An average age of 5 months was noted in one retrospective study. 16 Diagnosis In some cases, RCC causes retarded growth of the distal ulnar physis, which can result in shortening, external torsion, and procurvatum of the radius. Clinically this is observed as a torsion-angulation deformity of the distal antebrachium. 3,12,16 If RCC is bilateral, so should be the resulting antebrachial deformities. Radiographically, RCC is characterized by a radiolucent core of cartilage extending from the distal ulnar physis proximally to the metaphysis, ranging in length from 2 to 6 cm. 3,16 This core may be surrounded by a zone of sclerosis (Figure 8). 3 Although the size of the core can be impressive, it is important to note that there is no known correlation between size of the lesion, histology, and severity of angular deformity. 3 Figure 8. A 10-week-old, male g reat Dane evaluated after an injury to his right thoracic limb. An incidental finding is presence of bilateral retained cartilage cores ( r CC) in the distal ulna. Lateral (A) and craniocaudal (B) images of the distal right forelimb; the area outlined in the box in B is enlarged to highlight the presence of the r CC (arrow). Courtesy Dr. Dan Bucy, University of California–Davis Veterinary Medical Teaching Hospital A B