Page 1000 - Adams and Stashak's Lameness in Horses, 7th Edition

966 Chapter 9

Careful inquiry may reveal that an area has been over­ is a relatively frequent cause of foot pain and should be
looked or the veterinarian may need to shift the focus to considered in severely lame Standardbreds that have no
VetBooks.ir again. It is also important to remain aware of the poten­ in the winter months.
localizing signs. Acute lameness is seen after a race, often
soft tissue structures rather than just injecting the horse
Distention of the distal interphalangeal joint is a non­
tial for joint infection following intra‐articular injec­
tions. Onset of clinical signs can be delayed as long as 2 specific sign that may be noted in conjunction with foot
weeks if steroids are used. soreness. Radiographic signs of coffin joint arthritis may
An acceptable venue to watch a horse in hand can be or may not be present because synovitis can be a reflec­
difficult to find at the racetrack, and Standardbreds are tion of inflammation in nearby structures, including the
not always amenable to jogging on a lead, making obser­ podotrochlear apparatus. Response to intra‐articular
vation of the horse in the shed row typical. Unsound medication is generally favorable but often must be
trotters sometimes prefer to pace at slow speeds; how­ repeated, especially if an accurate diagnosis is never
ever, the pace is a forgiving gait, and front limb lameness made.
may be difficult to detect. Most horses, including pac­
ers, will finally trot in hand after several attempts.
Correlation between lameness seen in hand and that at Pastern
racing speed is often poor, so observation of horses in The pastern region is often overlooked in the
harness on the track is routine. Standardbred. Many practitioners are not as familiar
Flexion tests are part of most exams, although their with the intricate anatomy of this area, so soft tissue
value is dubious. The carpus can be flexed exclusively injuries are likely underdiagnosed. Injury to the distal
and this manipulation is generally useful. In the hindlimb, sesamoidean ligaments, collateral ligaments, and flexor
an effort should be made to flex the fetlock separately tendons in the pastern can all result in lameness and
from the upper limb, because problems are relatively even joint instability, causing ringbone months or even
common in this joint. years later.
A few points regarding the use of diagnostic analgesia
in the Standardbred deserve mention. Foot pain is so Fetlock
commonplace that blocking of a front limb should
always begin with anesthesia of the palmar digital nerves Synovial or joint capsule inflammation is common
to establish the significance of heel pain in the overall and develops as the amount of training increases. The
picture. The abaxial sesamoid block is avoided because condition can be secondary to altered gait from another
it can desensitize the foot, pastern, and parts of the fet­ lameness issue, and it is frequently seen in horses with
lock. Inadvertent anesthesia of fetlock pain could be sore heels as a result of toe‐first landing. Heat and effu­
mistaken for lameness of the foot, with dire conse­ sion are present along with a positive response to joint
quences if a fracture is present. Hindlimb foot pain is manipulation, but overt lameness is not typical. Fibrosis
infrequent, so digital anesthesia is rarely warranted; and mineralization of the synovial pad can occur with
however low plantar anesthesia should be used to rule chronicity resulting in a decreased range of motion.
out the distal limb for all but the most obvious cases of Osteochondral fragments are frequently encountered
hindlimb lameness. Observation of the horse on the in the fetlock, most commonly originating in the dorso­
track before and after diagnostic analgesia can be use­ medial proximal margin of the first phalanx. Concurrent
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ful; but there is risk of further injury, so the driver should thickening of the synovial pad is frequently observed
be instructed to only drive the horse as far as is neces­ because the two sites make contact during maximal
sary to assess the effectiveness of the block and to avoid extension of the joint. Small fragments may not be a
abrupt stops or turns. Propagation of incomplete frac­ significant problem, but larger fragments close to the
tures or catastrophic breakdown is possible following articular surface result in lameness and can produce
desensitization of a limb. Finally, the veterinarian must score lines on the metacarpal condyle. Frequent injec­
remember to abide by local jurisdictions regarding the tion may keep horses going, but fragment removal is the
use of local anesthetics close to race day. treatment of choice to prevent joint deterioration.
Proximal palmar/plantar osteochondral fragmenta­
tion of the first phalanx is a frequent radiographic find­
ing in Standardbreds. These lesions are routinely
SPECIFIC LAMENESS CONDITIONS removed prior to the onset of a racing career. Not all
Foot fragments cause lameness, and when they do it is mild.
The complaint more often involves an inability to go
Standardbreds race on compacted limestone tracks straight or breaks at high speed. Most fragments are
and are shod frequently, predisposing them to foot pain. found medially in the left hindlimb, and horses with an
It is not uncommon for a horse to be foot sore for sev­ outwardly rotated hindlimb axis are predisposed.
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eral days after a race. The long‐toe, low‐heel hoof con­ Demonstration of the lesion requires oblique views
formation seen in many Standardbreds, along with the angled 30°–45° distad to prevent overlap of the proxi­
repetitive concussion sustained from jogging on hard mal sesamoid bones on the palmar/plantar aspect of the
tracks, predisposes them to corns. Horses that are shod first phalanx. Problematic fragments can often be man­
tight or have the heel of the shoe turned in to prevent it aged using intra‐articular therapy until the end of the
from being pulled off if they overreach are likely to racing season without risk of further injury to the joint.
develop bruising from the focal pressure placed on the Arthroscopic removal of axial fragments is then indi­
caudal angle of the bars. Fracture of the distal phalanx cated, but the value of this has come into question.
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