The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.
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SPONSORED BY A21 TheHorse.com/AAEP2017 March 2018 THE HORSE AAEP Wrap-Up This can lead to hock inflammation and more need for hock injections. It might also cause stifle and/or gluteal pain. Underrun Heels Abnormal heel confor- mation should be easy to recognize, said Turner. The horse will have a broken- back hoof-pastern axis and a "bull-nosed" dorsal hoof wall. The horse's frog is usually large and pushed down below the hoof wall, bearing the horse's full weight when placed on the ground. Fortunately, said Turner, damage to the hind heels is usually easier to correct than damage to the front, "possibly due to the difference of the load encountered on the hind limbs vs. the forelimbs." Medial-Lateral Imbalance When the horse moves, his hind limbs naturally have a slight rotation to them. "This is necessary to ensure that the feet are wider than the forelegs when galloping," Turner said. "In many animals this causes … the hoof capsule to be high on the inside." This uneven wear can lead to suspen- sory injuries, fetlock lameness, and hock and tibia (the long bone between the hock and stifle) pain. The goal when addressing this imbal- ance, he said, is to get the horse to bear weight evenly and equally on his hind feet. Rear hoof imbalances are not well- understood. "Instead of causing foot pain directly, rear feet seem to cause many more problems higher up the leg—to the hocks, stifles, glutes, sacroiliac joint," said Turner. Addressing these asymmetries is just as important for treating or prevent- ing lameness as it is in the front hooves. In closing, he stressed the importance of X rays when assessing rear imbalances, keeping in mind the natural differences in rear hoof shape and alignment. Detecting Soft-Tissue Injuries in Hooves: Ultrasound vs. MRI When horses sustain injuries to the soft-tissue structures within their hooves, veterinarians rely on imaging for diag- nosis. Unfortunately, said Myra Barrett, DVM, MS, Dipl. ACVR, "the foot is par- ticularly challenging to image—there are only so many ways we can see it." The gold standard is MRI. However, it's cost-prohibitive for some owners and not all veterinarians have access to a unit. Radiography can reveal problems, but it's more useful for bony structures than soft tissue. And ultrasound is useful for imag- ing tendons and ligaments in other areas of the body, but it hasn't been clear how it stacks up to MRI for imaging the hoof. So Barrett, an assistant professor of veterinary diagnostic imaging at CSU and colleagues compared the two in a prospective study. The researchers performed ultrasound on horses that underwent MRI at CSU to compare injuries to the deep digital flexor tendon (DDFT), collateral sesamoidean ligament (CSL), and the navicular bursa (NB) within the hoof. They placed the ul- trasound transducer between the horses' heel bulbs to view the internal structures. Barrett said they hypothesized that ul- trasound would detect fewer lesions than MRI, which could cause veterinarians to underestimate the severity of the injuries. The team evaluated 70 ultrasound and MRI exams of 45 horses. They found that: ■ Ultrasound allowed veterinarians to di- agnose DDFT tears with 85% sensitivity (the ability to correctly identify those with the ailment), 60% specificity (the ability to correctly identify those with- out the injury), and 70% accuracy. With it they accurately diagnosed 36% of mild lesions, 74% of moderate lesions, and 100% of severe lesions; ■ For diagnosing NB effusion (swelling), ultrasound's sensitivity was 65%, speci- ficity 69%, and accuracy 67%; ■ For evaluating NB proliferation (excess tissue growth) its sensitivity was 47%, specificity 78%, and accuracy 61%; ■ For diagnosing CLS enlargement, ultrasound had 42% sensitivity, 78% specificity, and 61% accuracy; and ■ DDFT tearing below the navicular bone was evident on MRI in 27 limbs, 20 of which also had DDFT damage above the navicular bone that was apparent on both MRI and ultrasound. Barrett said it's common for horses to sustain soft-tissue and bony injuries within the hoof simultaneously, which are difficult to differentiate on ultrasound. Ultimately, Barrett said, the team determined that ultrasound is a useful screening tool for assessing DDFT le- sions, especially moderate to severe ones and those that occur above the navicular bone, but it could cause veterinarians to underestimate NB and CSL lesions. h e Visit TheHorse.com/AAEP2017 ■ A Shorter RLP Application Time Is Still Effective, TheHorse.com/40218 COURTESY DR. MYRA BARRETT Ultrasound could help vets screen for DDFT lesions. MRI and ultrasound of this horse's hoof capsule reveal a tear in that tendon. Hoof Wraps @HoofWraps Look at these little hooves at the @AAEPHorseDocs trade show!