Page 283 - The Veterinary Care of the Horse

NERVE BLOCKS

• The pain is usually abolished by an injection of local anaesthetic into the navicular bursa.
VetBooks.ir However, this is technically difficult and is only carried out by equine vets with

experience of the technique.

• The lameness is usually significantly reduced with a palmar digital nerve block.
• In some horses, the pain from navicular syndrome is alleviated by intra-articular

analgesia of the coffin joint.

The palmar digital and coffin joint blocks are not specific for navicular pain as they
desensitize structures other than the navicular bone, and so the results are interpreted together

with those from other tests such as X-rays.

When the pain is removed from the most obviously lame foot, the horse often shows
lameness in the opposite leg. This is because the condition usually affects both front feet but

is more advanced in one limb than the other. When the navicular regions of both front feet
are desensitized, the horse often becomes sound and has an increased stride length.

RADIOGRAPHIC CHANGES

Changes which may be seen on the radiographs of a horse with navicular syndrome include:
• a cyst within the bone (Figure 6.55)

• bony proliferations (known as enthesiophytes) at the site of attachment of the supporting

ligaments to the navicular bone
• enlarged vascular channels on the distal (lower) border of the navicular bone

• an increase or decrease in density of the bone

• changes to the flexor surface of the bone in contact with the DDFT, e.g. new bone
deposits, loss of bone density or change in outline caused by erosions, loss of definition

between the cortex (outer part) of the bone and the medulla (the central part of the bone)
• small fragments of bone on the lower border of the navicular bone.