The long-term objective of this research is to develop non- or minimally-invasive techniques that will improve our ability to identify Thoroughbred racehorses at increased risk of catastrophic proximal sesamoid bone (PSB) fracture. A dual advantage of our approach will be gaining an understanding of how PSBs remodel in response to exercise and how PSB bone quality is affected by racing and race training.

Despite advances in imaging modalities, such as nuclear scintigraphy, which have allowed us to identify horses at increased risk of catastrophic humeral, tibial and pelvic stress fractures, catastrophic PSB fracture remains the leading cause of racehorse fatalities in New York. There are currently no imaging modalities or diagnostic tests that can help the veterinarian or horse trainer identify impending PSB fracture. Our approach builds upon a currently-existing CT imaging database of TB racehorse fetlocks by bolstering racehorse fracture and control numbers and adding a non-racehorse control population. We propose to test several non-invasive imaging modalities (i.e., clinical CT, micro-CT, DXA, and Raman spectroscopy) to measure PSB mineral density as compared to gold-standard destructive ash fraction measurements. Finally, we will determine whether these quantitative measurements can improve the ability of epidemiological models to accurately predict PSB fracture.

Specific Aim 1. To determine whether proximal sesamoid bone volume fraction, bone mineral density and fetlock osteoarthritis (OA) differ between: 1) racehorses sustaining PSB fracture, 2) racehorses not sustaining PSB fracture and 3) non-racehorses. Bone volume fraction and fetlock OA will be assessed using clinical and micro-CT. Bone mineral density will be assessed as described in Aim 2 (5 distinct modalities).

Specific Aim 2. To determine how well PSB ash fraction measurements, the gold-standard for measuring bone mineral density, correlate with non-invasive measurements of bone mineral density, including: 1) clinical CT, 2) micro-CT, 3) dual-energy x-ray absorptiometry (DXA), 4) Raman spectroscopy and 5) Raman and ash fraction measurements of the iliac crest.

Specific Aim 3. To determine whether PSB or iliac crest bone mineral density measurements or PSB bone volume fraction measurements increase the likelihood of appropriate classification of fractures or controls as compared to a previously reported mathematical model.