Grayson Jockey Club Research Foundation

Current Projects

		Grayson Jockey Club Research Foundation Bucked Shin Project
Figure 1. Young horse with bucked shins		Catastrophic fractures in thoroughbred racehorses represent a significant problem for the entrire racing industry. Epidemiological studies sponsored by the Grayson-Jockey Club Research Foundation have begun to outline risk factors for fatal injuries associate with training and shoeing practices. The study currently being conducted has demonstrated fatigue failure of bone as being and important component of these catastrophic injuries. The Bucked Shin Complex, or Dorsal Metacarpal Disease, is a condition that starts in young healthy sport horses, usually Thoroughbreds or Quarterhorses undergoing intensive training for racing. This disease not only causes afflicted animals significant pain, but it is also very costly as it results in the animal having to be rested and withdrawn from racing and training or periods ranging from several weeks to months. There is growing evidence from previous studies conducted at the New Bolton Center (University of Pennsylvania) that training programs have much to do with contributing to the onset of Bucked Shins. It is hypothesized that failure to adequately expose the horse to racing or similar stress conditions prior to racing, denies the horse the chance to build bone structure compatible to performing under these conditions, and hence puts the bone at risk for failure. The purpose of the present study is to continue to evaluate the efficacy of a modified training program. Primary Investigators Dr. Ray Boston and Dr David Nunamaker (VMD). Anatomy of the horse leg Diagnosis The diagnosis of bucked shins is not usually provided by the trainer or owner of the horse. It is usually indicated by a history of acute tenderness or soreness of the left or both Metacarpal III (MC III) bones following high speed workouts or after a race, immediately after or up to a day later. Physical examination will reveal pain on the dorsal or dorsomedial aspect of the third Metacarpal, this may also be accompanied by swelling and tenderness which would indicate new bone proliferation in the affected area. *Treatment* Previously, veterinarians have been taught that bucked shins were the result of microfractures on the dorsal surface of MC III, thought to be due to fatigue injuries that occur during high speed work. Subsequent investigations have suggested a different understanding of the etiology of bucked shins which lead to the formation of the hypothesis that high strain cyclic fatigue causes reduced bone stiffness which in turn leads to the bone increasing its inertial properties in compensation first using lamellar bone and later using fiber type bone. Fiber bone forms much faster than lamellar bone, so if the bone stiffness decreases quickly enough for the bone to change from lamellar formation to periosteal/fiber formation, bucked shines can result.
	Figure 2. Young horse with bucked shins
Figure 3. Severe secondary bucked shins (Saucer fracture)
	Figure 4. Apositional bone growth of normal young horse (histology)

Biomathematics Unit