Ununited Anconeal Process, Ununited Medial Coronoid Process, Ununited Medial Epicondyle, Patella Cubiti, and Sesamoidal Fragments of the Elbow

Osteoarthritis of the elbow has been recognized byveterinarians for many years to be a developmental diseasesyndrome in young dogs. It was not until the middle 1950s,however, that progress was made toward defining specificpathologic etiologies, with the elucidation of the problem of"ununited anconeal process." Originally thought to beanalogous to patella cubiti in humans,(13)the true nature of these ectopic sesamoid bones was soonrealized,(3) thereby categorizing an initialcause of elbow osteoarthrosis. In the early 1960s the term"elbow dysplasia" was offered as an alternative to theterm ununited anconeal process, since it was believed by some tobetter describe the generalized osteoarthritis syndrome thatinvolved the entire elbow joint of animals afflicted with thatdisease.(2) Thus for several years the term"elbow dysplasia" was used synonymously with ununitedanconeal process in the veterinary literature,(6,10,14) in spite of the recognition bymultiple authors that secondary degenerative joint disease ofthe elbow in young dogs did, indeed, occur in joints havingintact anconeal processes. In 1966 Ljunggren and co-workerscorrectly pointed out this misuse of terminology and redefinedthe syndrome of elbow dysplasia, describing the three causesthen known for its development: ununited anconeal process,ununited medial epicondyle, and patella cubiti.(9) Corley further refined terminology bydescribing elbow dysplasia as "a descriptive term appliedto a developmental abnormality of the elbow joint that ismanifested as an early osteoarthritis with or without anununited anconeal process."(4) Hisdefinition has been respected by many subsequent authors.(7,8,11) More recently, numerous conditions,both congenital and developmental, have been described that maybe incorporated under the heading of elbow dysplasia as definedby Corley. (1,5,12) The frustrations ofdealing with the term elbow dysplasia as a definitive diagnosisin a computerized records system and the subsequent inability todecipher epidemiologic features of specific causes of elbowosteoarthrosis have been aptly demonstrated by Hayes andco-workers.(7) While a review of all thecauses of elbow dysplasia far exceeds the scope of the immediatediscussion, several causes of the syndrome will be reviewed inthe following pages. An understanding of this evolution ofterminology will hopefully aid the reader who is interested inreviewing the veterinary literature on these topics.