Comparison of macrostructural and microstructural bone features in Thoroughbred racehorses with and without midbody fracture of the proximal sesamoid bone

Abstract

Fractured PSBs had adapted to high loading but had focal evidence of excessive remodeling and porosity that likely predisposed the horses to complete fracture and catastrophic injury. Detection of focal injury before complete fracture provides an opportunity for prevention of catastrophic injury. Development of diagnostic imaging methods to assess porosity of PSBs may help to identify at-risk horses and allow for modifications of training and racing schedules to reduce the incidence of PSB fracture in Thoroughbred racehorses.

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

“…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- …”

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

“…Comminuted proximal sesamoid fractures were the most common configuration in the current study (58%; 14/24), while American studies reported mid-body (Anthenill, Gardner et al 2010) and basilar fractures (Parente, Richardson et al 1993) being more common. Alternatively, fractures of the carpal bones, first phalanx and third metacarpal bone were largely noncatastrophic.…”

“…Calcein labels highlighting active osteonal bone formation was mainly seen towards the dorsal epiphysis, suggesting that modelling occurred towards the cancellous regions of the condyle in horses in the training group rather than an increase in size (Boyde and Firth 2005). Bone modelling towards cancellous bone regions was also seen in another experimental study of proximal sesamoid bones, with microradiography showing densely compacted cancellous bone in both the proximal sesamoid fracture and non-proximal sesamoid fracture groups (Anthenill, Gardner et al 2010). Similar to earlier in vitro bone studies discussed earlier, these studies reduced confounding by restriction or matching to gender, breed and age (Boyde and Firth 2005, Davies 2005, Davies 2006, Anthenill, Gardner et al 2010.…”

“…Bone modelling towards cancellous bone regions was also seen in another experimental study of proximal sesamoid bones, with microradiography showing densely compacted cancellous bone in both the proximal sesamoid fracture and non-proximal sesamoid fracture groups (Anthenill, Gardner et al 2010). Similar to earlier in vitro bone studies discussed earlier, these studies reduced confounding by restriction or matching to gender, breed and age (Boyde and Firth 2005, Davies 2005, Davies 2006, Anthenill, Gardner et al 2010. It is therefore not unreasonable to assume that the increased exposure to exercise would be directly proportional to increased bone modelling, in particular towards the region of highest strain (McCarthy and Jeffcott 1992, Carstanjen, Lepage et al 2003, Hiney, Nielsen et al 2004, Firth, Rogers et al 2005b).…”

“…Hence, fatigue fractures occur in consistent locations and follow predictable paths through bones exemplified by lateral and medial condylar fractures of third metacarpal/tarsal bones (Riggs 2002), mid-body fractures of proximal sesamoid bones (Anthenill, Gardner et al 2010), distal tibia and proximal humerus (O'Sullivan and Lumsden 2003). The mechanisms by which the equine skeleton adapts to decreasing demands of exercise or periodical intervals of rest are less well understood.…”