DIAGNOSTICS ISSUE 31_Jerkins feature.qxd 10/02/2014 12:19 Page 2
DIAGNOSTIC IMAGING
DIAGNOSTIC IMAGING
Predicting future soundness The quest to own or train the perfect racehorse can have many starting points. For many people the search for the Holy Grail begins at the yearling sales, where horsemen from around the globe inspect and agonize over young horseflesh, dreaming and hoping of attaining that future champion. A prominent part of this process is the pre-sales veterinary examination, which usually includes the reading of a set of repository radiographs of the prospective purchase.
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WORDS: THOMAS O’KEEFFE PHOTOS: FRANCES J KARON, THOMAS O’KEEFFE
EW issues spark more debate and controversy than the interpretation of a juvenile Thoroughbred’s radiographs and their relevance to the horse’s future racing career. This article aims to review the most common radiographic finding, sesamoiditis, in the Thoroughbred yearling and discusses new research published in 2013 exploring the link between sesamoiditis and suspensory branch injuries and the effect these conditions can have on soundness and racing performance. This research can provide horsemen with accurate information with respect to the risk associated with these conditions and can aid them in the selection process and training of the young Thoroughbred racehorse.
Anatomy of Suspensory Apparatus The recently deceased top sire and multiple Grade 1 winner Harlan’s Holiday and the Australian phenomenon that is Black Caviar are two high profile examples of Thoroughbreds who suffered suspensory branch injuries during their racing careers. The suspensory ligament’s function is crucial to a horse’s movement since it prevents excessive extension of the fetlock joint during the weight-bearing phase of the stride, and it is the combination of skeletal and soft tissue structures that make up the suspensory
apparatus that allow the racehorse to fulfill its athletic potential. The suspensory apparatus consists of the suspensory ligament and its extensor branches, the proximal sesamoid bones, and the distal sesamoidean ligaments. The suspensory ligament bifurcates into lateral and medial branches one-half to twothirds down the cannon, and the branches insert mainly onto the proximal sesamoid bones. Sesamoiditis is thought to be an indicator of inflammation of the proximal sesamoid bone at the insertion site of the suspensory ligament branches. The focus of much scrutiny and examination is the suspensory branch itself, as injuries that cause a loss of integrity to where it attaches to the sesamoid bone can result in an inability of the ligament to function properly. Clinical signs of suspensory branch injuries vary depending on the severity and chronicity of the lesion and usually include heat and swelling. There may be fetlock joint distension in some cases due to the close proximity of the suspensory ligament to the joint capsule. Pain on palpation of the branch is present during the acute stage but lameness is not a consistent feature of this condition and should not be used as a barometer of severity or clinical progress. Ultimately, diagnosis is relatively straightforward based on clinical signs and ultrasonography. Ultrasound features of this
injury include fiber pattern disruption, altered echogenicity, ligament enlargement, and in moderate to severe cases a core lesion within the branch may be identified.
Research performed in horses in training Despite the high prevalence of the condition and the economic loss that can be suffered as a result of a suspensory branch injury, the subject has been poorly investigated until recently. Ultrasound examinations are being performed with a greater frequency now as part of a pre-purchase examination and ultrasound abnormalities of the suspensory branch are found with enough frequency to warrant further investigation into their significance. The presumption is and has been that these abnormalities indicate the presence of current or previous injury and infer potential future weakness, thereby influencing the saleability of these horses. However this viewpoint is based on anecdotal observations, and it has not been until this year that a more detailed look at the condition has been performed. Pete Ramzan and colleagues at Rossdales and Partners in Newmarket, U.K., published a study in May of 2013 in the Equine Veterinary Journal, where they completed ultrasounds on sixty racehorses in training known to be free of history and clinical signs of suspensory
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