Developmental orthopedic disease: problems of limbs in young horses

Abstract

he term developmental orthopedic disease (DOD) was coined in 1986 to encompass all orthopedic problems seen in the growing foal and has become the generally accepted term. It came out of a Blue Ribbon Panel sponsored by the American Quarter Horse Association. It is a term that encompasses all general growth disturbances of horses and is therefore nonspecific. It is felt that one has to be nonspecific when talking about the various limb abnormalities of young horses because previous terms such as metabolic bone disease and osteochondrosis implied that they all had a common cause and pathogenesis. It is still to be determined how closely related the various forms of DOD may be, but it is important that the term not be used synonymously with osteochondrosis. It is considered inappropriate for all subchondral cystic lesions, physitis, angular limb deformities, and cervical vertebral malformations to be presumed to be manifestations of osteochondrosis (a condition subsequently defined). The spectrum of conditions currently classified as DOD was previously designated as metabolic bone disease. However, it is felt that this term is misleading because it refers specifically to bone, whereas many of these problems are seen essentially as joint and growth plate problems. Severe forms of DOD are seen sometimes when there is little or no aberration in bone histomorphometry, implying questionable change in bone metabolism. Before defining the various syndromes of developmental orthopedic disease, some basic developmental anatomy is appropriate. Long bones develop from cartilage by a process of endochondral ossification. Ossification develops in the center of the future long bone (diaphysis) and also at the ends of these long bones (epiphysis). As ossification proceeds, a bony epiphysis and a bony diaphysis form.