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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

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  • 1 Equine Medical Center of Ocala, 7107 W Hwy 326, Ocala, FL 34482.
  • | 2 Orthopedic Institute-Gainesville, 4500 Newberry Rd, Gainesville, FL 32607.
  • | 3 Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77845.
  • | 4 Gulfstream Racetrack and Casino, 901 S Federal Hwy, Hallandale Beach, FL 33009.
  • | 5 Equine Medical Center of Ocala, 7107 W Hwy 326, Ocala, FL 34482.

Abstract

Objective—To compare bony changes in the metacarpophalangeal joint (MCPJ) of racehorses with (cases) and without (controls) biaxial proximal sesamoid bone (PSB) fracture as determined by 2 grading scales applied to images of cadaveric forelimbs obtained by means of standing MRI (sMRI).

Design—Case-control study.

Sample—Forelimbs from 74 Thoroughbred racehorses (21 cases and 53 controls) that were euthanized at a Florida racetrack.

Procedures—Both forelimbs were harvested from cases and controls. Each forelimb underwent sMRI to obtain images of the MCPJ. Two grading scales were described and used for image evaluation; one assessed the density of the PSBs, and the other assessed the integrity of the subchondral bone (SCB) plate at the distopalmar aspect of the third metacarpal bone (MC3). Logistic regression was used to compare the grades between case and control limbs.

Results—Biaxial PSB fracture was associated with a total PSB grade (sum of lateral and medial PSB grades) ≥ 5 for the fractured limb, total MC3 SCB grade (sum of lateral and medial MC3 SCB grades) ≥ 5 for the contralateral limb, and the presence of orthopedic disease in the contralateral MC3.

Conclusions and Clinical Relevance—For cases with biaxial PSB fracture, the density of the PSBs in the affected limb was greater and the MC3 of the contralateral limb was more likely to have orthopedic disease, compared with those for controls. Further evaluation of sMRI as a screening tool for identification of racehorses at risk of biaxial PSB fracture is warranted. (J Am Vet Med Assoc 2015;246:661–673)

Abstract

Objective—To compare bony changes in the metacarpophalangeal joint (MCPJ) of racehorses with (cases) and without (controls) biaxial proximal sesamoid bone (PSB) fracture as determined by 2 grading scales applied to images of cadaveric forelimbs obtained by means of standing MRI (sMRI).

Design—Case-control study.

Sample—Forelimbs from 74 Thoroughbred racehorses (21 cases and 53 controls) that were euthanized at a Florida racetrack.

Procedures—Both forelimbs were harvested from cases and controls. Each forelimb underwent sMRI to obtain images of the MCPJ. Two grading scales were described and used for image evaluation; one assessed the density of the PSBs, and the other assessed the integrity of the subchondral bone (SCB) plate at the distopalmar aspect of the third metacarpal bone (MC3). Logistic regression was used to compare the grades between case and control limbs.

Results—Biaxial PSB fracture was associated with a total PSB grade (sum of lateral and medial PSB grades) ≥ 5 for the fractured limb, total MC3 SCB grade (sum of lateral and medial MC3 SCB grades) ≥ 5 for the contralateral limb, and the presence of orthopedic disease in the contralateral MC3.

Conclusions and Clinical Relevance—For cases with biaxial PSB fracture, the density of the PSBs in the affected limb was greater and the MC3 of the contralateral limb was more likely to have orthopedic disease, compared with those for controls. Further evaluation of sMRI as a screening tool for identification of racehorses at risk of biaxial PSB fracture is warranted. (J Am Vet Med Assoc 2015;246:661–673)

Contributor Notes

Presented in abstract form at the Convention of the American Association of Equine Practitioners, Anaheim, Calif, December 2012; the Convention of the American College of Veterinary Surgeons, San Antonio, Texas, October 2013; and the Convention of the British Equine Veterinary Association, Birmingham, England, September 2014.

The authors thank Nina Ubide and P. J. Campo for technical assistance.

Address correspondence to Dr. Peloso (jpeloso@emcocala.com).