Page 349 - The Veterinary Care of the Horse

Intra-articular and regional analgesia – nerve blocks

Nerve blocks are often used to localize the cause of the lameness or to confirm that a
VetBooks.ir particular joint is the source of the pain. If local anaesthetic injected into a joint abolishes the

lameness, then the cause is usually within the joint. The result is not always straightforward
because analgesia of a particular joint may only reduce rather than eliminate the lameness,
showing that other factors are playing a part (see Nerve Blocks, page 105). It is important to

be aware that there is a risk of infection when a joint is injected with local anaesthetic or
medication

Ultrasonography

Ultrasonography is increasingly used in the diagnosis of joint disease as the modern,

sophisticated ultrasound machines provide excellent images of the soft tissues of a joint and
the bony surfaces.

Magnetic Resonance Imaging (MRI) and Computed Tomography

(CT)

Magnetic resonance and computed tomography images provide good detail of the joint

structure and can detect pathological changes in the tissues before they are visible on X-ray
or with ultrasound. The limitation is the cost of the procedure. The joints that can be imaged
in this way include the hock, knee, fetlock, pastern and coffin joints. MRI has improved our

ability to diagnose the various causes of palmar foot pain. A CT scan may useful for complex
fractures and those that are not clear on radiographs.

Scintigraphy

Scintigraphy will highlight any regions of increased blood flow and active remodelling of
bone. It may be helpful in localizing joint problems that do not yet show up on radiographs.

The technique is also useful for imaging joints such as the hips and sacroiliac joints that
cannot be X-rayed in the standing horse. It can provide valuable information when multiple

joint problems are contributing to the lameness.

Synovial fluid examination

Valuable information can be obtained by examination of the synovial fluid. The joint to be
examined is prepared by clipping and thorough cleaning with a surgical scrub. The fluid is