Abstract
SummaryBackgroundSuperficial digital flexor tendon (SDFT) injury is an important health and welfare concern in racehorses. It is generally diagnosed with ultrasonography, but predictive ultrasonographic features have not been reported.ObjectivesTo determine ultrasonographic features of forelimb SDFT injury at initial presentation in Thoroughbred racehorses that could predict a successful return to racing (completing ≥5 races).Study designRetrospective cohort study.MethodsDigitised ultrasonographic images of 469 horses with forelimb SDFT injuries from the Hong Kong Jockey Club (2003–2014) were evaluated, using a previously validated ultrasonographic scoring system. Six ultrasonographic parameters were evaluated (type and extent of the injury, location, echogenicity, cross‐sectional area and longitudinal fibre pattern of the maximal injury zone [MIZ]), as well as horse signalment, retirement date and number of races before and after injury. Data were analysed by generalised linear regression with significance at P<0.05.ResultsCases were divided into two groups: 1) For cases of SDFT tendonitis with core lesions, cross‐sectional area at the MIZ was the most significant factor determining a successful return to racing (P = 0.03). If the lesion was <50% of the total cross‐sectional area, horses had 29–35% probability of successfully racing again, but if it was ≥50% this decreased to 11–16%. 2) For cases of SDFT tendonitis without a core lesion, longitudinal fibre pattern at the MIZ best predicted a successful return to racing (P = 0.002); if the affected longitudinal fibre pattern was <75% of the total, horses had 49–99% probability of successfully return to racing, but if it was ≥75% this decreased to 14%.Main limitationsPrognostic information may not be applicable to other breeds/disciplines.ConclusionsThis is the first study to describe ultrasonographic features of forelimb SDFT injuries at initial presentation that were predictive of successful return to racing. The outcomes will assist with early, evidence‐based decisions on prognosis in Thoroughbred racehorses.
Highlights
Superficial digital flexor tendon (SDFT) tendonitis is common in racehorses [1,2] and is likely to curtail their athletic career
The prevalence of SDFT tendonitis in flat Thoroughbred horses is between 3.4% and 11.1% [1,4] and this injury is responsible for 14% of all retirements at the Hong Kong Jockey Club (HKJC) [2]
Digitised ultrasonographic records of 1161 horses with a forelimb SDFT injury sustained while training or racing at the HKJC between 2003 and 2014 were reviewed retrospectively
Summary
Superficial digital flexor tendon (SDFT) tendonitis is common in racehorses [1,2] and is likely to curtail their athletic career. The prevalence of SDFT tendonitis in flat Thoroughbred horses is between 3.4% and 11.1% [1,4] and this injury is responsible for 14% of all retirements at the Hong Kong Jockey Club (HKJC) [2]. Less than 50% of horses will return to racing, and 56% of those will re-injure [5,6]. Many different imaging modalities may be used to evaluate tendons. The central core region or the periphery of the tendon may be affected, experimental studies have suggested a predisposition to the former [8,9]. The size of the lesion may vary in terms of the proportion of the cross-sectional area of the tendon affected and the length of the injury.
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