Page 89 - September 2020

anced and bring the leg into proper alignment) may be all that is needed for correction.
Corrective trimming often helps, because the inevitable uneven hoof growth that results from the angulation can accentuate the asym- metry. “With a valgus deviation (in at the joint) the outside of the foot overgrows and needs trimming, while a varus deformity does the same to the inside of the foot. Application of a glue-on shoe with an inside or outside extension will also help the foal to bear weight more evenly. Another non-invasive method of treatment was studied about 10 years ago in the United Kingdom, looking at application of extracorporeal radial shock waves to the convex side of the physis to help correct significant angulations,” says Schramme.
If conservative treatment doesn’t correct the deformity enough, or in time (within 4 weeks), surgical alternatives should be considered. Surgical options available include periosteal stripping and transphyseal bridging. “For many years veterinarians have been stripping the peri- osteum over the concave side of the physis, but some now feel that most of these foals would have straightened on their own without it,”
says Schramme. Some of the studies evaluating the efficacy of periosteal stripping did their research on normal foals (creating the angular limb deformity and then correcting it), and criticism of those studies was that the findings in normal foals cannot be extrapolated to foals that actually have an angular deformity.
Many equine surgeons still use this strip- ping technique because it is a quick, benign surgery that can be done on an out-patient basis and does not involve further follow-up surgeries. “The alternative technique, transphy- seal bridging of the faster growing side of the physis, necessitates revision surgery at a later date to remove the bridge--before the deformity overcorrects and results in a deformity in the opposite direction. Once the limb is overcor- rected, the situation is infinitely worse. Surgical bridging involves putting in screws with or without wires across the physis, or staples across the physis; there are different methods that can be used,” he says.
“In severe cases (an angulation of 12 to
15 degrees or more in the carpus), or in older patients that are getting toward the end or even beyond the optimum time window of opportunity, we won’t use periosteal strip- ping; we always use transphyseal bridging. In these instances, you need all the correction
you can get, and with the bridging you create immediate compression across the physis and it will stop growing--whereas with the stripping you’re just hoping the other side will catch up.” There has to be a lot of growth potential left, for it to do that.
FLEXURAL DEFORMITIES
Some foals have relatively upright pasterns that get worse as the foal grows, becoming
a club foot. “We refer to this as a flexural deformity of a joint rather than use the term ‘contracted tendon’ because it is more accu- rate,” says Schramme. “It is often very difficult to determine which tendon is involved, but the affected joint can always be named. You can refer to the joint that is knuckled or misshapen. The coffin joint and the fetlock joint are most commonly affected by this condition, with the carpus being a distant third.
“Typically, you’ll see flexural deformity of the coffin joint in weanlings (club foot), and of the fetlock joint in yearlings. The latter will show straight pasterns or even a knuckling forward in the fetlock. The cause of these problems is a bit of a mystery. We think it’s a discrepancy in growth between the tendons (or their check ligaments) and the long bones. The bones may be growing faster than the tendons and check ligaments, though this is very dif- ficult to prove,” Schramme says.
Another possibility is that a contracture of the muscle develops, due to pain or decreased weight bearing. “If a foal has a fracture or an in- fected joint that creates lameness and reluctance to put weight on that limb, you will soon see the joints in the limb contract because of the pain and decreased weight bearing,” he says. This is
a vicious cycle; the less the leg is used, the more the muscle contracts, and the more it contracts, the less the tendon can be loaded normally.
Treatment involves loading those tendons and muscles as much as possible, to get them to stretch, or to induce muscle relaxation. “But if you try to do that without painkillers, it will just cause more pain, and the situation will deteriorate further. It
is a challenge; you must try to increase the loading but at the same time make the animal pain free. We try things like leverage arms, extensions and elevations in the shoe to get an optimal biome- chanical effect in loading,” he explains.
“In a club foot we’ll put a toe extension on the shoe. In a fetlock contraction we’ll put a heel elevation on the shoe, as well as a toe extension. If you flex the coffin joint with a heel eleva- tion, you are relaxing the deep flexor tendon. Consequently, the animal must put more weight on the superficial flexor tendon. By relaxing
the one tendon, you hope the other tendon gets loaded more. Since the superficial flexor tendon and muscle are thought to be the functional unit responsible for fetlock flexural deformities of the fetlock, elevation of the heel is recommended.
“The purpose of using a toe extension in the treatment of flexural deformity of the fetlock
is to delay the break-over during the weight bearing phase of the stride--to increase the du- ration of loading on the flexor tendons, thereby
Fetlock deformities must be corrected before the foal is 2-3 months old because growth in this area has almost stopped by this age.
Some foals have relatively upright pasterns that get worse as the foal grows, becoming a club foot, which is referred to as a flexural deformity of a joint.
putting more pull on those tendons. With both types of flexural deformity, the initial treat- ment consists of controlled exercise, corrective orthopedic shoeing, and pain relief. Splints can also be used, to force the leg back into a more normal posture. Splints also induce an inverse reflex; whereby contracted muscles may relax. You also want to balance the ration and slow the growth of that animal.
“If improvement is not seen after four weeks of this conservative management or if the con- dition deteriorates in spite of treatment, surgery is required. For flexural deformity of the foot (coffin joint), surgical treatment consists of cut- ting the inferior check ligaments, then continu- ing on with nutritional adjustment, orthopedic shoeing, and exercise. For flexural deformities of the fetlock, surgical treatment consists of cutting both the inferior and superior check ligaments. All the management tactics are continued after surgery, but now with a better chance for correction,” he explains.
As long as only the check ligaments are cut, the horse still maintains potential for becoming a useful athlete (for riding, racing, or whatever career is desired). “In very severe cases (foals with a dorsal hoof wall beyond the vertical, or yearlings with a fetlock that is permanently
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SPEEDHORSE September 2020 87