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Home / Equine Research Bank / Equine Vet J / Subchondral lucencies of the medial femoral condyle in yearl...
Equine veterinary journal2023; doi: 10.1111/evj.13945

Subchondral lucencies of the medial femoral condyle in yearling and 2-year-old Thoroughbred sales horses: Prevalence, progression and associations with racing performance.

Abstract: Subchondral lucencies (SCLs) in the distal aspect of the medial femoral condyle (MFC) of young Thoroughbred horses are a source of controversy on presale radiographs. There is limited scientific evidence regarding the risk of progression and impact on future racing performance. Objective: To (1) identify the prevalence of MFC SCLs on sales repository radiographs in yearling and 2-year-old Thoroughbreds; (2) identify any association between grade of MFC SCL and future racing performance and (3) monitor changes in MFC SCL grades between yearling and 2-year-old sales. Methods: Prospective cohort study. Methods: Radiographs were obtained with consignor permission from a 2016 yearling sale and five 2017 2-year-old sales. Stifle radiographs were evaluated and MFC SCLs graded on a scale of 0-3. Axial MFC lucencies were recorded separately. Maximum MFC grades per horse were analysed for associations with racing performance outcomes, adjusted for sex, to the end of the horses' 4-year-old racing year. Analysis was via logistic, negative binomial or linear regression as appropriate, with the threshold for significance set at α = 0.05. Results: Radiographs from 2508 yearlings (5016 stifles) and 436 2-year-olds (872 stifles) were included in the study. MFC SCLs of grades 1-3 were observed in 242 (9.65%) yearlings and 49 (11.2%) 2-year-olds. Bilateral MFC SCLs of grades 1-3 were observed in 54 (2.2%) yearlings and 12 (2.8%) 2-year-olds. Grade 1 MFC SCLs in yearlings either remained unchanged (14/31), progressed to a grade 2 (6/31) or resolved (11/31) by the 2-year-old sale. Grade 2 MFC SCLs in yearlings remained unchanged (6/10), progressed to a grade 3 (2/10) or improved to a grade 1 (2/10). Yearlings with a grade 3 MFC SCL had a 78% probability of starting a race (95% confidence interval [CI] 58.2-89.6%), compared with an 84% probability of racing for grade 0 yearlings (95% CI 82.7-85.8%). Six of the seven yearlings with axial MFC lucencies raced. Conclusions: This study may underestimate the prevalence of severe lesions in the general yearling population of U.S. Thoroughbreds. However, the convenience sample used is representative of the population of interest at sales. The study design could not address exclusions prior to sale. Conclusions: Grade 1 MFC SCLs are the most common type seen in yearling and 2-year-old sales horses. The majority of yearling grade 1 MFC SCLs resolved or remained static by 2-year-old sales. It was also possible for grade 2 and 3 MFC SCLs to improve one grade between sales. Fewer sales yearlings with a grade 3 MFC SCL raced, but in those that did race there was no evidence of worse performance compared to unaffected peers. Axial MFC lucencies did not affect racing performance.
© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2023-06-22 PubMed ID: 37345448DOI: 10.1111/evj.13945Google Scholar: Lookup
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Summary

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The research primarily investigates the prevalence of subchondral lucencies in the medial femoral condyle in young Thoroughbred horses, their potential progression, and any possible impact on the horses’ future racing performance.

Study Design and Methodology

  • The study is a prospective cohort study where researchers used radiographs taken from a yearling sale in 2016 and five 2-year-old horse sales in 2017.
  • The research team graded the subchondral lucencies in the medial femoral condyle (MFC SCLs) on horses with a 0-3 scale.
  • The team used regression models to analyze the Max MFC grades in relation to future racing outcomes.
  • The study looked at potential variables like sex and adjusted for these in their analysis.

Results of the Study

  • The researchers included radiographs from 2508 yearlings and 436 2-year-olds in the study.
  • The study found MFC SCLs in approximately 10% of the yearlings and 2-year-olds, with about 2% showing bilateral MFC SCLs.
  • There was evidence of possible progression in the condition of the MFC SCLs between the yearling and two-year-old sales.
  • Yearlings with grade 3 (the highest severity grade) MFC SCL had a slightly lower probability of starting a race as compared to those with grade 0.
  • The axial MFC lucencies did not appear to impact racing performance.

Conclusions of the Study

  • The researchers suspect that their study may underestimate the prevalence of severe lesions in the general yearling population of U.S. Thoroughbreds due to the sample size and limitation in their study design like limitations to account for exclusions before the sale.
  • Among MFC SCLs, grade 1 is the most commonly observed in yearlings and 2-year-olds being sold.
  • The majority of the yearlings having grade 1 MFC SCLs either had resolved or remained static by the time of the 2-year-old sale. And for higher-grade MFC SCLs (grade 2 and 3), a one-grade improvement between sales was possible.
  • There was no evidence suggesting worse performance in racing for those horses that raced despite having a grade 3 MFC SCL, compared to their unaffected peers.

The researchers conclude that while MFC SCLS are prevalent in yearling and 2-year-old Thoroughbreds and could progress, they do not necessarily impact the horses’ future racing performance.

Cite This Article

APA
Peat FJ, Kawcak CE, McIlwraith CW, Keenan DP, Berk JT, Mork DS. (2023). Subchondral lucencies of the medial femoral condyle in yearling and 2-year-old Thoroughbred sales horses: Prevalence, progression and associations with racing performance. Equine Vet J. https://doi.org/10.1111/evj.13945

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Peat, Frances J
  • Orthopaedic Research Center, C. Wayne McIlwraith Translational Medicine Institute, Colorado State University, Fort Collins, Colorado, USA.
Kawcak, Christopher E
  • Orthopaedic Research Center, C. Wayne McIlwraith Translational Medicine Institute, Colorado State University, Fort Collins, Colorado, USA.
McIlwraith, C Wayne
  • Orthopaedic Research Center, C. Wayne McIlwraith Translational Medicine Institute, Colorado State University, Fort Collins, Colorado, USA.
Keenan, David P
  • Matamata Veterinary Services, Matamata, New Zealand.
Berk, Jeffrey T
  • Equine Medical Associates, Lexington, Kentucky, USA.
Mork, Daniel S
  • Department of Statistics, College of Natural Sciences, Colorado State University, Fort Collins, Colorado, USA.

Grant Funding

  • Grayson-Jockey Club Research Foundation
  • Keeneland Association Ltd
  • Fasig-Tipton Ltd
  • Barbara Banke
  • Bridlewood Farm
  • Flaxman Holdings
  • Maria Niarchos
  • John & Jerry Amerman
  • Foxwood Stables
  • Three Chimneys Farm
  • Ashford Stud
  • John Magnier
  • Dr Mark Dedomenico
  • Consignors & Commercial Breeders Association (Lexington, Kentucky)
  • Marty & Pam Wygod
  • Gary West
  • Dr Ryan Carpenter
  • Antony Beck
  • Gainesway Farm
  • Spendthrift Farm
  • Denali Stud
  • Victoria Chapman

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