Racing performance of juvenile Thoroughbreds with femoropatellar osteochondrosis at auction: A retrospective case-control study.

Abstract

Osteochondrosis dissecans (OCD) is common in the femoropatellar joint in Thoroughbred yearlings for sale at auction and there is no consensus on the effect on racing outcomes. Describe femoropatellar OCD in juvenile Thoroughbreds and compare the racing performance of affected Thoroughbred horses to siblings and unaffected horses from the same sale. Retrospective case-control study of juvenile horses born 2010-2016. Radiographic reports from 27 Thoroughbred auctions of weanling (5-11 months of age) and yearling (12-22 months of age) horses were reviewed to identify femoropatellar OCD. Age and sex of cases and controls were obtained from the sales catalogue. Racing performance was obtained from an online database. Correlation between lesion characteristics and racing performance were assessed using Pearson and Spearman correlations for continuous and ordinal/categorical variables respectively. Racing performance was compared between cases and sibling controls and age- and sex-matched sale number controls from the same sale with Poisson distribution and log link. Significance level of alpha = 0.05 was used. Femoropatellar OCD was identified in 429 horses with North American race records. OCD was present on 519 lateral trochlear ridges and 54 medial trochlear ridges. There were more males in the case group (70%) than in the sibling control group (47%). Case racing performance was compared to 1042 sibling and 757 hip controls. There were significant but small decreases in racing metrics of cases and increases in males for years raced, total starts, starts for 2-5 years of age, total placings, and placings at 2-4 years of age. Analysis of specific lesion metrics revealed weak correlations for performance outcomes (positive and negative) resulting in an inability to draw firm conclusions. Retrospective study where case management was unknown. Femoropatellar OCD in juvenile Thoroughbreds for sale at auction decreases some racing outcomes.