available for treatment of bone-related lameness, but has not been validated
for the treatment of distal tarsal osteoarthritis to date.
Cunean Tenectomy
Cunean tenectomy and the Wamberg modification of this procedure are
purported to alleviate pressure over the dorsomedial aspect of the small tarsal
joints. One survey of the owners of 285 performance horses with bone spavin,
reported that results of cunean tenectomy were rated as excellent or good in
83% of patients and that lameness resolved within 8 weeks following cunean
tenectomy. The authors speculated that tenectomy reduced rotational and
shearing forces during contraction of the tibialis cranialis muscle, resulting in
less pain (Eastman 1997). Calling the procedure into question are reports
describing similar results between 2 groups of racing Thoroughbreds. One
group was treated with cunean tenectomy in addition to other medical therapy
and shoeing changes, and the other group had the same measures without
surgery (Gabel et al. 1979).
Arthrodesis and facilitated ankylosis
The aim of arthrodesis is to remove sufficient cartilage to allow continuity of
bone across the joint space. In spite of many variations of this technique
having been used, the success rate of surgical arthrodesis is consistently
reported to lie between 59 and 85% (Dechant 1999; Zubrod et al. 2005). The
most common cause for dissatisfaction following surgical arthrodesis is the
pr otracted convalescence to soundness (average 7.5 months; range 3.5 to 12
months) (Edwards 1980). Techniques creating 3 single distinct drill paths
have proven to cause minimal postoperative morbidity with generally good
outcomes. Drill size varies from 2.7 to 4.5 mm with similar results. A 3.2-mm
drill bit compromises nicely between sufficient rigidity to drill without breaking
while having just enough flexibility to follow the joint space without bypassing
islands of cartilage, and 3 drill paths seem to suffice. The success of the
procedure depends upon creating solid spot welds of bony bridging to
immobilize the joints. Most surgeons treat both the TMT and DIT joints
regardless of diagnostic indications of the source of pain. The drill bit must
stay within the joint space and therefore intra-operative imaging is considered
imperative. While minor distal penetrations do not affect the outcome, damage
to the margins of the joints may cause exostoses, enlargement, and potential
gait compromise. If the PIT joint is involved, the prognosis is less favorable,
but it too should be operated, because this offers the best hope of a complete
recovery. Horses are stall rested until the skin sutures are removed and hand
walking is allowed for an additional 2 weeks, when light riding is begun.
Horses should not be turned out for a minimum of 2 months to avoid joint
instability.
Techniques of chemical arthrodesis (monoiodoacetic acid or ethyl alcohol)
have been proposed to require a shorter convalescence time in comparison
with surgical arthrodesis by inducing cartilage necrosis, and presumably
leading to ankylosis of the DIT and TMT joints. Soundness in horses 12
months after MIA injection of the distal tarsal joints has been reported in
15-‐18
February
2016
East
London
Convention
Centre,
East
London,
South
Africa
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