Bone Spavin, a Dutch View Sciences, Faculty of Veterinary Medicine, Utrecht University, the Netherlands.
Bone spavin can be defined as an osteoarthrosis of the distal tarsal joints, in which the changes may be localised in the central tarsal bone, the third tarsal bone and/or the proximal joint surface of the third metatarsal bone. In the pathogenesis three stages can be discriminated that correlate well with the clinical signs. These stages are fibrillation of the articular cartilage, osteolyis and ankylosis. The first stage can already be observed in young horses (6 - 9 months of age) and can predominantly be found at two predilection sites on the articular cartilage of the distal intertarsal joint. The lesions can then develop further in the direction of the subchondral bone plate where osteolytic lesions may develop. In this stage horses commonly start to show clinical signs of lameness. In some cases the lesions will proceed further until, after complete destruction of the original cartilage layers, a complete ankylosis develops. If that stage is reached, clinical signs usually subside and the horse becomes free of lameness. In the Netherlands, the prevalence of bone spavin has decreased dramatically in the past few decades from more than 5% in the early 1980s until less than 1% now. In fact, nowadays bone spavin can be considered a rare disease in the riding horse that hardly plays a role in pre-purchase examinations. The reason for this decrease in prevalence is the strong and consistent selection, as has been performed by the Royal Dutch Warmblood Studbook (KWPN) in the past years. This selection was based on two main criteria: conformation and radiographic quality. It has been shown in the Dutch Warmblood that there is a strong relationship between a faulty conformation in the hock region (sickle hocks but also extremely extended hocks and abnormal outward rotation during the stance phase) and the occurrence of bone spavin (Barneveld 1983). Further, the heritability of bone spavin diagnosed radiographically has been estimated in the Dutch Warmblood at 0.20 to 0.35 (van der Veen et al. 1994). This means that a stallion with bone spavin has 1.6 times as many offspring with bone spavin, as a stallion without. Selection has been rigorous in the past period and no stallion with radiographic evidence of bone spavin and/or a faulty conformation of the hock has been approved. It is evident that this strict policy has had the desired effect. _______________________________ Judy http://icehorses.net http://clickryder.com
