Page 703 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 669

trimming and physiological shoeing (Figure 5.69). the end of the shoe. Fitting the shoe in this manner will
Horses with tarsal pain or bone spavin may attempt to change the conformation of the distal limb and the
VetBooks.ir by redistributing their weight. The first indicator of a phase of the stride. To help reduce weight, wide‐webbed
angulation of the hock during impact and the stance
unload the dorsal (front) aspect of the small tarsal joints
wedged (flat) aluminum shoes are used in some show
DT problem may be the pattern of shoe wear. When a
horse that has been wearing the hind shoes level from horses, but one has to be cautious when applying a
heel to toe begins to wear the toe excessively, it may be wedge to low heels as this may increase pressure on
an indication that the horse has altered its gait in an these structures. A lateral trailer or a lateral extension of
effort to minimize extension. A second indication of a the shoe tends to stop excessive twisting of the limb.
hock problem may be dragging of the toe on the affected However, these devices may be contraindicated in horses
limb(s). However this has also been described in horses that have to stop and turn quickly, because the extension
that have pathology involving the stifle. Excessive toe may dig into the footing and stop the distal limb
wear may be the result of the horse trying to minimize abruptly, causing abnormal torque on the distal limb
hock flexion and carrying the hoof in a low arc of flight. joints. Common shoeing recommendations for horses
Low or underrun heels affecting the health of the foot, with DT OA include lateral (outside) extensions or trail-
or as a cause of lameness, are often overlooked in the ers, heel elevations, and rolled or squared off toes. 107
hindfeet and may contribute to lameness of the distal
hock joints. Underrun or collapsed heels in the hindfeet
may lead to subtle bilateral lameness, which is often Advanced Treatment Procedures
attributable to hock, stifle, or back pain. Low heels or Surgical Arthrodesis of DIT and TMT Joints
short shoes allow the ground surface of the hoof at the
heels to move forward, changing the conformation of When bone spavin becomes refractory to systemic
the distal limb, which alters the angulation of the hock. treatment and intra‐articular medications, more aggres-
Damage to the heels of the hindfeet is easier to improve sive therapy may be warranted. The natural resolution
than in the forefeet, possibly due to the anatomy and the of advanced OA (bone spavin) is ankylosis. Ankylosis
difference of the load encountered on the hindlimbs. can stabilize the joint sufficiently enough to minimize
Hindlimb foot management is aimed toward improv- the pain creating lameness (Figure 5.70). However,
ing foot conformation and to facilitate break‐over by ankylosis is unpredictable and can take some time to
shortening the toe by squaring and/or rolling the toe of progress to soundness. This rarely happens without sur-
the shoe if necessary. Shoes to the hindfeet are fit the gical intervention, and therefore surgical arthrodesis
same as the front where a line is drawn across the widest techniques have been developed to help accelerate joint
part of the foot and the shoe is fitted so the line is placed fusion. 1,4,6,33,48,91,129,150,151 The optimal treatment for
in the middle of the shoe. In the hindfeet, the branches arthrodesis of the DT joints should be minimally inva-
3
of the shoe will extend beyond the end of the heels. The sive, create widespread necrosis of the chondrocytes and
appropriate length of the hind shoe can be determined destruction of the articular cartilage matrix, cause little
by dropping a vertical line from the bulb of the heel to to no discomfort for the horse during the treatment
period, lack serious complications, and be affordable.
A variety of techniques have been developed for
surgical arthrodesis of the DT joints. Currently, intra‐
articular drilling of the joint spaces is the most widely
used means to promote surgical arthrodesis. Focal
mechanical destruction of the articular cartilage and
subchondral bone via “three‐path” technique with
removal of less than 60% of the cartilage is probably the
most common arthrodesis technique (Figure 5.71).
Variations in technique include size of drill bit, use of
bone graft, and degree of radiographic or fluoroscopic
control utilized during the procedure. The drill tracts
eventually heal with a bridging callus, which crosses the
joint space acting to stabilizing the joint in a manner
similar to spot welding of metal. One study found that
of 36 horses having the three‐drill tract procedure per-
formed, 66% were able to return to their previous levels
of performance. An additional 14% of horses improved
33
after surgery, but did not meet the criteria to be consid-
ered successful. In that study, no clinical, radiographic,
or surgical factors were beneficial in predicting clinical
outcome; however, there was a trend toward improved
outcome when precise radiographic monitoring of the
33
drilling procedure was performed at surgery. The
major disadvantages of this technique include expense
Figure 5.69. When shoeing the hindfeet in horses with DT OA, and prolonged convalescence, which ranges from 4 to
it is important to extend the branches of the shoe beyond the end of 12 months. There is also a concern that results in upper‐
the heels. Source: Courtesy of Dr. Steve O’Grady. level competition horses are less favorable. Careful