Incomplete ossification of the humeral condyle in Vietnamese pot-bellied pigs.

ABSTRACT

The purpose of this study was to evaluate the occurrence of humeral condylar fractures in Vietnamese pot-bellied pigs and to postulate a possible predisposing cause for these fractures. Thirteen Vietnamese pot-bellied pigs (Group A) were evaluated over an eight year period (1990-1998), each with a history of either a unilateral or bilateral forelimb lameness. The cause of lameness was localized to the elbow region. Of the thirteen pigs, twenty-one elbows were evaluated radiographically. Pigs ranged in age from six months to four years old. All pigs over the age of seven months showed radiographic evidence of elbow degenerative joint disease. Fractures involving the medial aspect of the humeral condyle were identified in 8/21 studies (38%). A well-defined linear intracondylar articular lucency was identified in 7/21 studies (33%) on the craniocaudal projection. The site of this lucency corresponded to the location of the articular component of the fractures seen involving the humeral condyle. The elbows of five pot-bellied pigs with no known history of forelimb lameness or trauma (Group B) were evaluated radiographically following euthanasia. All five pigs were of unknown age and gender. An intracondylar vertical linear lucency was identified bilaterally in three pigs (60%). Concurrent degenerative joint disease was present in all instances. The remaining two pigs were radiographically normal. Computed tomography of the elbows was performed in one affected pig from Group B. The radiographic findings in this pig were verified. Histopathology of the right elbow of this affected pig was diagnostic for incomplete endochondral ossification of the humeral condyle. A similar condition involving the humeral condyle has been previously described in Cocker and Brittany Spaniels. These canine breeds also have a high incidence of humeral condylar fractures. It is postulated that Vietnamese pot-bellied pigs are similarly prone to humeral condylar fractures, even in the absence of known trauma, due to incomplete ossification of the humeral condyle.