Page 209 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

184 CHAPTER 1

VetBooks.ir improve after a short period of work, whereas severe Muscle wastage, especially of the gluteals, may be iden-
tified but is not specific to this problem. Horses that
cases tend to worsen with exercise. Generally, lame-
ness will worsen with hard work and rest may improve
the hind feet, although again, such changes are not
it, although some horses will appear “stiff” when drag the hindlimbs may scuff or square-off the toe of
restricted to the box. Affected horses are presented limited to this pathology.
with a range of gait abnormalities, none of which are
specific for OA of the distal tarsal joints. These may Differential diagnosis
include a reduction in the height of the foot flight arc Occult spavin; OCD; proximal suspensory ligament
and shortening of the cranial phase of the stride, toe desmitis; stifle problems; talocalcaneal OA; cunean
dragging, axial swing of the foot during protraction tendon bursitis.
and landing on the lateral wall, and asymmetric move-
ment of the tuber coxae. These signs may be accentu- Diagnosis
ated with the worse limb on the inside or, occasionally, Intra-articular analgesia of the small tarsal joints
the outside when the horse is worked in a circle. Flexion is important to confirm the source of pain. Since
of the affected limb (spavin test) for 60 seconds usually <40% of horses have a physical communication
results in an exacerbation in the degree of lameness; between the TMT and DIT joints, some clinicians
however, due to the stay apparatus of the hindlimb, it is recommend injecting both joints either separately
not only the hock that has been stressed. Thickening of or in combination. Many clinicians, however, inject
the periarticular soft tissues resulting in enlargement the TMT joint first and assess the response before
on the medial aspect of the hock is an unusual find- attempting the more difficult DIT joint block. It can
ing that may occur in more chronic cases (Fig. 1.353). be hard to establish the exact location of the nee-
dle when attempting to inject the distal intertarsal
joint and radiographic guidance can be very useful.
1.353 Published work has proved that local anaesthetic
solutions freely communicate between the lower
two joints. The response to these blocks should be
assessed 10 minutes after injection and again 40–60
minutes after injection. An improvement in the
degree of lameness of >50% is considered positive
following these blocks. If the condition is bilateral,
then an exacerbation in lameness in the contralateral
hindlimb is expected. Failure to alleviate lameness
using these blocks does not rule out the condition,
with a tibial and peroneal nerve block required in
some cases to improve the lameness. It should be
remembered that a deep branch lateral plantar nerve
block can also affect discomfort arising from the dis-
tal tarsal joints, and local anaesthetic solution within
the TMT joint can provide analgesia to the proximal
metatarsal region, including the proximal part of the
Fig. 1.353 This horse was presented with a history suspensory ligament. Assessing the effect of local
of chronic bilateral hindlimb lameness that was analgesia on the response to a flexion test may be
diagnosed after radiographs and intra-articular misleading and is therefore not recommended.
analgesia as bone spavin. Note the distal medial Radiography is always used in the diagnostic pro-
enlargements in both hocks due to soft-tissue filling cess, using four views for each hindlimb. It is impor-
over the spavin region (arrows). (Photo courtesy tant to centre the beam accurately to evaluate the
Graham Munroe) small tarsal joints. Signs of the disease are usually