34
46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
increase the loading of the short side of the limb, encouraging growth on that side
and subsequent limb straightening. I prefer Equilox® extensions over shoes, as the
shoes tend to result in hoof and heel contracture. It is important to prepare the foot
properly with a rasp and hoofknife to maximise adherence of the acrylic to the foot.
Take care to avoid the exothermic acrylic contacting the coronary band, or being
left in the sulcus of the frog. The extension should not extend to the toe region (i.e.
past the breakover point), and the side that is extended should be slightly higher
than the other wall.
Surgical intervention is reserved for foals with severe deviations, those not
responding to conservative management or those showing deterioration. Surgical
intervention is based on one of two basic principles; growth acceleration or growth
arrest. Periosteal elevation is purported to accelerate growth on the short side of
the limb. There has been increasing questions raised regarding the efficacy of this
procedure. It is seldom used in isolation – restriction of exercise and corrective
trimming/extensions is usually used in conjunction with periosteal stripping.4 Over
the last 15 years the number of periosteal strips I have performed has continued to
decrease. If the foal is anaesthetised for implant placement in the fetlock, and the
carpus has a mild deviation, I tend to perform the appropriate periosteal strip on the
carpus in hopes of avoiding the need to perform additional surgery on the carpus
down the track.
Growth arrest is achieved by transphyseal bridging, with transphyseal screws and
wires, staples, or a single screw placed across the longer side of the limb.5-8 All the
above mentioned procedures will produce the desired limb straightening, and all
procedures require implant removal (to avoid over correction) once the limb is
straightened. Transphyseal screws and wires tend to result in a poorer cosmetic
outcome – white hairs and visible thickening of the leg at the surgery site is not
uncommon. If the implants become infected, there is a significant risk of the
infection extending to the physis or joint.
A single transphyseal screw has the advantage of being easier to place than screws
and wires, has a longer window of opportunity for correction, and has a better
cosmetic outcome.5 The single screw does have the potential to permanently
damage the growth plate, and this can occasionally lead to over correction. Up until
the 2012 season, 3.5 mm cortical screws were used in the fetlock in our practice.
Although these resulted in adequate correction, the 3.5 mm screw can make
removal problematic. There is increased risk of the screw head (which is quite
shallow) stripping, and breakage of the screw, especially at the junction between the
screw head and the shaft. A difficult screw removal can also contribute to a poor
cosmetic outcome. In the last two seasons we have been using 4.5 mm self-tapping
cortical screws and are believe they are easier to remove and the cosmetic outcome
is acceptable. In the carpus, 4.5 mm self-tapping cortical screws are used.
Under general anaesthesia and in lateral recumbency, aseptic preparation of the
region is performed. The g rowth plate is identified and a stab incision performed 11.5 centimetres proximal. Using the 3.2 mm drill bit positioned perpendicular to the
long axis of the bone, the drill is engaged in the cortex to a depth of 3 approximately
3 mm. Once seated, the drill is then redirected to cross the growth plate at a 70degree angle on the same side of the leg. The drill is usually flush with the leg to
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