Catastrophic biaxial proximal sesamoid bone fractures in UK Thoroughbred races (1999–2004): Horse characteristics and racing history

Abstract

There is a strong association between type of racing surface and PSBF. Horses competing in flat races on all weather surfaces have an increased risk of PSBF. These fractures appear to happen in experienced horses with several starts, with few fractures occurring within the first season of racing. Further research should focus on identification of underlying pathology of these fractures. Epidemiological studies aimed at the identification of risk factors for PSBF in the UK racing population would require a large number of cases acquired over many years given the relatively low incidence of PSBF.

Association of catastrophic biaxial fracture of the proximal sesamoid bones with bony changes of the metacarpophalangeal joint identified by standing magnetic resonance imaging in cadaveric forelimbs of Thoroughbred racehorses

“…50 In the present study, the number of starts was significantly associated with biaxial PSB fracture when it was modeled as a continuous variable but not when it was modeled as a dichotomous variable ( Table 1). Results of multiple studies 14,15,17,47 suggest that biaxial PSB fracture is associated with chronic use and the risk of biaxial PSB fracture increases as the number of race starts increases. In 1 study, 17 intensive training and racing caused microstructural changes at the tissue level that predisposed Thoroughbred racehorses to acute complete PSB fractures.…”

“…6,7,[14][15][16][17]47,48 In the present study, ipsilateral limbs had significantly higher PSB grades (ie, PSB densification) and contralateral limbs had significantly higher total MC3 SCB grades and were more likely to have orthopedic disease of MC3, compared with control limbs. We propose that horses with biaxial PSB fracture of a forelimb have preexisting pathological lesions in the contralateral MC3 that cause those horses to favor the contralateral limb during training and racing.…”

“…Results of necropsies performed in other studies indicate that biaxial (medial and lateral) PSB fracture is the most common cause for failure of the MCPJ for racehorses in California, 7,13 Kentucky, 2 Florida, 4,b,c and Hong Kong a and an uncommon cause for failure of the MCPJ for racehorses in the United Kingdom. 10,14,15 Histologic evaluation has identified structural changes in the PSBs of trained versus untrained Thoroughbreds. 16,17 Results of a study 17 in which histomorphometric analysis was used to evaluate the PSBs indi-…”

“…Results of necropsies performed in other studies indicate that biaxial (medial and lateral) PSB fracture is the most common cause for failure of the MCPJ for racehorses in California, 7,13 Kentucky, 2 Florida, 4,b,c and Hong Kong a and an uncommon cause for failure of the MCPJ for racehorses in the United Kingdom. 10,14,15 Histologic evaluation has identified structural changes in the PSBs of trained versus untrained Thoroughbreds. 16,17 Results of a study 17 in which histomorphometric analysis was used to evaluate the PSBs indicate that bony material is more compacted in horses with biaxial PSB fracture, compared with that of horses without biaxial PSB fracture, and the investigators concluded that early identification of that structural change could provide an opportunity for prevention of PSB fractures.…”

Fracture incidence rates and the association of rest with bone remodelling in Thoroughbred racehorses at the Hong Kong Jockey Club

“…Racing in the United States are conducted almost exclusively on all-weather dirt surfaces which are firmer compared to turf surfaces in the United Kingdom and Australia. Firmer surfaces has been shown to be a greater risk factor for catastrophic fractures in various studies published worldwide (Williams, Harkins et al 2001, Parkin, Clegg et al 2004a, Parkin, Clegg et al 2004d, Oikawa and Kusunose 2005, Kristoffersen, Parkin et al 2010b. Differences also exist in governance and racing rules.…”