Vet Comp Orthop Traumatol 2023; 36(05): A1-A27
DOI: 10.1055/s-0043-1775657
Podium Abstracts

Thoroughbred Racehorse Age and Athletic Training History Influence Superficial Digital Flexor Tendon Structure–Function Adaptation

S. Durgam
1   College of Veterinary Medicine, The Ohio State University, Ohio, United States
,
C. Moreno
1   College of Veterinary Medicine, The Ohio State University, Ohio, United States
,
S. Long
1   College of Veterinary Medicine, The Ohio State University, Ohio, United States
,
S. Seabeck
1   College of Veterinary Medicine, The Ohio State University, Ohio, United States
,
M. Samol
2   CA Animal Health and Food Safety Board, University of California, Davis, California, United States
,
T. Garcia-Nolen
3   Veterinary Orthopedic Research Laboratory, University of California, Davis, California, United States
,
F. Uzal
2   CA Animal Health and Food Safety Board, University of California, Davis, California, United States
,
M.C. Stewart
4   College of Veterinary Medicine, University of Illinois, Urbana-Champaign, Illinois, United States
,
S. Stover
3   Veterinary Orthopedic Research Laboratory, University of California, Davis, California, United States
› Author Affiliations
› Further Information
 

Introduction: The pathophysiological mechanisms responsible for superficial digital flexor tendon (SDFT) injuries in Thoroughbred racehorses are poorly understood. This research aims to determine if Thoroughbred SDFT fascicles and interfascicular matrix (IFM) characteristics undergo structure–function adaptations reflective of the horse's age and athletic training.

Materials and Methods: Mid-metacarpal SDFT (n = 50) from 2-, 3-, and 4-year-old Thoroughbred racehorses necropsied through CAHFS were preserved within 48 hours of death/euthanasia. Longitudinal and transverse histological sections were imaged (light and confocal microscopy) for quantifying fascicle CSA, IFM thickness, and IFM elastin area fraction %. Biochemical total tendon elastin (FASTINTM) was quantified. Cyclical and load-to-failure tensile testing of whole tendons and fascicle/IFM units were conducted. Data were analyzed with mixed-model ANOVA and univariate logistic regression (p < 0.05).

Results: Fascicle CSA in the lateral, core, and medial SDFT were significantly different in all age groups. SDFT core fascicle CSA of 3 years old was 30% decreased (p = 0.01) than 2 years old. In contrast, IFM thickness of 3 years old was 28% increased (p < 0.01) than 2 years old. Total elastin in lateral SDFT of 2 years old (6%; p = 0.032) was greater than 3- (4.2%) and 4 years old (4.4%), respectively. Tendon pre-yield modulus (R = 0.455; p = 0.009) and yield stress (R = 0.4; p = 0.021) were positively correlated with increasing age and races per year of active training.

Discussion/Conclusion: The decreased fascicle CSA and elastin in the SDFT core offers a potential mechanistic explanation for core lesion predisposition in THB racehorses. Elastin, a noncollagen glycoprotein, largely localized to the IFM, and its impact on tendon tensile function will shed light on developing and assessing training regimens, and ultimately, reduce SDFT injury incidences.

Acknowledgements: Grayson Jockey Club Research Foundation.



Publication History

Article published online:
11 September 2023

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