Page 178 - The Veterinary Care of the Horse

can be helpful in giving a prognosis for recovery or otherwise.

VetBooks.ir The timing of the examination

An injured tendon should not be examined by ultrasound until at least 72 hours after the
injury occurs. This is because the initial swelling either can obscure the extent of fibre

disruption or make the injury appear more severe than it is. Also, the destructive enzymes
released may still be causing further fibre damage. Usually the tendon is scanned again one

month later and then at intervals to monitor the healing. It should be rescanned before an
increase in the controlled exercise programme is recommended. If at any stage the serial
ultrasound examinations reveal signs of re-injury which are not clinically apparent, the

exercise regime is reduced.

Limitations of ultrasonography

• When a tendon is re-injured, it can be very difficult on the first examination to determine

which of the changes in appearance are due to the original injury and which are due to
the new one.

• The healing of the suspensory ligament can be difficult to assess with serial ultrasound

examinations as this ligament contains variable amounts of muscle tissue which look
darker on the scan and could be confused with a lesion.

• Only the surface of bones can be assessed as the ultrasound is reflected and does not
penetrate the deeper tissue.

SCINTIGRAPHY (BONE SCAN)

What is scintigraphy?

Scintigraphy is a tool that the vet can use to assist with the diagnosis of lameness or an
internal problem. A radioactive label is attached either to a drug or to white blood cells which

are attracted to the area being investigated.
In lameness cases, the scintigraphy performed is called a bone scan. The radioactive

substance injected (technetium) attaches to binding sites that are exposed when the bone is
actively remodelling or soft tissue is becoming mineralized. The increased metabolism of

calcium and activity of osteoblasts (bone forming cells) results in a higher concentration of
radioactive material at these sites. Thus radioactivity is highest at areas of increased bone

activity, such as a hairline fracture.