Page 809 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness Associated with the Axial Skeleton 775

artery in the hindlimb, and very rarely the brachial
artery in the front limb. Circulatory problems in the
VetBooks.ir in lameness. The etiology has been described as being
muscles (and later in all tissues) can cause pain, resulting
caused by the migrating larva of Strongylus vulgaris, but
it is not clear why only these locations are affected. It is
more likely that any damage to the intima of the blood
vessels can cause a thrombus to form.

Clinical Signs and Diagnosis
This lameness is specific in that it occurs after or dur-
ing work, is sudden in onset, and can be very severe
Figure 6.18. Radiograph of a horse with bone proliferation (grade 3–5 of 5) but can diminish or disappear within
between the coccygeal vertebrae 1 and 2 at the dorsal aspect as minutes to hours after ceasing work. Because of the
the result of an avulsion fracture of the intervertebral ligament.
severe pain, horses may sweat, show anxiety, and be
very restless, which can make the condition look like
chance of false‐negative findings is great. Prognosis is azoturia or even colic. Blood chemistry and a clinical
unfavorable because of the chance of development of oste- workup for colic are negative. 11,16
oarthritis of the coxofemoral joint, leading to permanent Clinical examination shows lower perfusion in the
and progressing lameness. 22 affected limb, lower temperature (thermography can be
useful in these cases), and absence or lower pressure of
Fractures of the Sacrum and Coccygeal Vertebrae arterial pulse. On the nonaffected limb, the veins can
show clearly, while they are indistinct on the affected
Fractures of the sacral bone (primarily dorsal processes) limb. Ultrasonography can show lower blood flow in
or coccygeal vertebrae are rare but can cause lameness. the blood vessels of the affected limb (using Doppler).
25
When the proximal coccygeal vertebrae are involved, the With transrectal ultrasonography it is sometimes possi-
normal locomotion pattern at the walk (the snakelike ble to find the thrombus and measure its size, but with
32
motion) and the canter can be influenced by pain in this a rectal examination one can determine the decrease or
region. Backing up (lowering the tail region) may be painful, absence of arterial pulse or fremitus in the iliac arteries.
and the horse may be reluctant or completely refuse to back
up. Often the owner regards this as a dominance problem
more than a physical issue. Some owners and trainers may Treatment and Prognosis
think the horse’s unwillingness to back up is showing the Treatment is focused on medication: anticoagulants
horse is not respectful to the handler and they do not under- (heparin 100 IU/kg sc SID, aspirin 5–10 mg/kg po SID,
stand there is a physical cause for this behavior (many disci- phenprocoumon 0.08–0.16 mg/kg IV initial bolus, grad-
plines use backing as an obedience test). Clinical examination ually reduced), nonsteroidal anti‐inflammatory drugs,
can show enlargement of the soft tissues in the sacral or and antimicrobial drugs (metronidazole 25 mg/kg PO
coccygeal region, and passive mobility can be painful. BID and thiabendazole 4 g/45 kg PO once weekly for 3
Radiography can be used to image the fracture site when weeks or ivermectin or moxidectin) to act against S. vul-
coccygeal vertebrae are involved (Figure 6.18), as can a lat- garis larvae when they are expected to be the cause. 16
eral image for sacral dorsal process fractures. Ultrasonography Successful surgical removal of the thrombus has been
is also a good tool for imaging this region, but scintigraphy performed with a thrombectomy catheter, but this requires
4
is the most sensitive. that the exact location of the thrombus be determined by
Treatment can focus on anti‐inflammatory therapy and ultrasonography or scintigraphy. 3,19,27 Prognosis for throm-
reducing the workload. When nerves are involved, caudal bosis of the aorta and the iliac arteries is guarded, especially
epidural steroid administration has been used to treat this when the underlying cause is not known.
condition successfully. Methylprednisolone acetate
17
(200 mg) mixed with 10–20 mL of saline can be used to
perform an epidural injection. Surgery may be indicated
when fracture fragments are displaced or sequestration References
occurs. The prognosis is generally good for a return to 1. Almanza A, Whitcomb MB. Ultrasonographic diagnosis of pelvic
athletic performance. Sometimes coccygeal fractures are a fractures in 28 horses. Proc Am Assoc Equine Pract 2003;
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Thrombus formation in arteries of the limbs can North Am Equine Pract 1999;15:223–246.
cause blood supply interruption. Specific locations for 6. Brown K. Pelvic fractures. In Current Therapy in Equine Medicine,
6th ed. Robinson E, Sprayberry KA, eds. Saunders, Philadelphia,
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