ORTHOPEDICS
Managing
Navicular Bone Disease B y
M a r i e
R o s e n t h a l ,
M S
Images courtesy of Dr. Roger Smith
To optimize the treatment of the navicular bone,
Radiographs of navicular disease (arrows).
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Issue 1/2020 | ModernEquineVet.com
one should not only pay attention to the navicular bone itself but also the surrounding soft tissue, because both can be involved in this region of the foot, Roger Smith, MA, VetMB, PhD, DEO, DipECVSMR DipECVS, FRCVS, explained at the BEVA Conference. “Making an accurate diagnosis requires localization of the lameness to the navicular region,” said Dr. Smith, which usually involves diagnostic analgesia and imaging. Although blocking will enable one to determine that the pain is in the foot, it’s usually not specific for navicular bone disease, according to Dr. Smith, who is a professor of equine orthopedics at the Royal Veterinary College. “We can localize it to the foot and while blocking the navicular bursa and the coffin joint may be a little bit more specific, it doesn't differentiate the soft tissue components from bony pathology. So ultimately we're going to require imaging,” he said. Radiographs can determine obvious signs of navicular disease and eliminate other causes of foot lameness, according to Dr. Smith. When looking at the radiograph, be careful not to over interpret the distal border fragments, he warned. “The significance of distal border fragments is questionable,” Dr. Smith explained. “They are more common in horses with lameness in this region, but can also occur in sound horses.” MRI can provide more information, because it can identify different abnormalities, such as deep flexor pathology and abnormalities of the navicular bone. “Successful treatment of that troublesome navicular bone requires defining the pathology, and I think MRI has made a big contribution to that,” Dr. Smith said. Early disease, which usually shows the presence of bone edema without obvious radiographic changes, has a better prognosis. If cases are found early, corrective farriery to reduce excessive biomechanical forces on the deep digital flexor tendon and navicular bone can be helpful. “The loading force of the navicular bone region and the deep flexor tendon is relatively low at the start of