Comparison of macrostructural and microstructural bone features in Thoroughbred racehorses with and without midbody fracture of the proximal sesamoid bone.
OBJECTIVE
To compare macrostructural and microstructural features of proximal sesamoid bones (PSBs) from horses with and without PSB midbody fracture to gain insight into the pathogenesis of PSB fracture.


METHODS
PSBs from 16 Thoroughbred racehorses (8 with and 8 without a PSB midbody fracture).


METHODS
Parasagittal sections of fractured and contralateral intact PSBs from horses with a PSB fracture and an intact PSB from age- and sex-matched control horses without a PSB fracture were evaluated for visual, radiographic, microradiographic, histologic, and his-tomorphometric differences in bone porosity, vascular channels, heme pigment, trabecular anisotropy, and pathological findings.


RESULTS
Fractured PSBs and their contralateral intact PSBs had more compacted trabecular bone than did control PSBs. Focal repair or remodeling was evident in the palmar aspect of many fractured and contralateral intact PSBs. Fracture coincided with microstructural features and propagated from the flexor to the articular surface.


CONCLUSIONS
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.
Anthenill
Lucy A
LA
J.D. Wheat Veterinary Orthopedic Research Laboratory, Departments of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA.
Gardner
Ian A
IA
Pool
Roy R
RR
Garcia
Tanya C
TC
Stover
Susan M
SM
D000818:Animals; D016723:Bone Remodeling / Q000502:physiology; D001947:Breeding; D050723:Fractures, Bone / Q000000981:diagnostic imaging / Q000473:pathology / Q000662:veterinary*; D006418:Heme / Q000378:metabolism; D006734:Horse Diseases / Q000473:pathology*; D006736:Horses; D008297:Male; D009919:Orchiectomy; D010805:Physical Conditioning, Animal / Q000379:methods; D011859:Radiography; D012420:Running / Q000502:physiology; D012716:Sesamoid Bones / Q000033:anatomy & histology* / Q000000981:diagnostic imaging
D006418:Heme