Subclinical ultrasonographic abnormalities of the suspensory ligament branches in National Hunt racehorses.

BACKGROUND

Suspensory ligament branch (SLB) desmopathy is a common cause of lameness and an important cause of lost training in the Thoroughbred racing industry. Studies have assessed the impact of insertional injuries of the SLB on the careers of flat racehorses and established the prevalence of subclinical ultrasonographic SLB abnormalities in this population, but little work has investigated SLB injury in National Hunt (NH) racehorses.

OBJECTIVES

To investigate the prevalence of subclinical ultrasonographic SLB abnormalities in NH racehorses with no clinical signs or history of SLB injury and to establish the cross-sectional area (CSA) of SLBs in this population.

STUDY DESIGN

Cross-sectional study using data collected from horses on an NH yard.

METHODS

Ultrasonographic examination of forelimb SLBs in 62 horses on a single NH yard was performed. Images were graded according to a previously reported system. CSA measurements were obtained from transverse images.

RESULTS

Nineteen of 62 horses had at least one SLB with grade 2 ultrasonographic abnormalities. Grade 2 ultrasonographic abnormalities occurred more frequently in the medial than the lateral SLB (P = 0.05). The medial SLB insertional CSA was significantly larger (P<0.001) than that of the lateral SLB.

MAIN LIMITATIONS

Length of time on the yard (and therefore available veterinary history) is variable in this population.

CONCLUSIONS

One in three NH racehorses without history or clinical signs of SLB injury had at least one SLB with a grade 2 ultrasonographic abnormality. The medial branch was over-represented. The medial SLB insertional CSA is larger than the lateral and thus comparison with the corresponding branch in the contralateral limb is recommended to avoid misdiagnosis of medial SLB enlargement.