Page 88 - September 2020

EQUINE HEALTH
Some young horses suffer from skeletal abnormalities that are present at birth, such as crooked legs and joint flexural problems, while others develop skeletal problems during the first months or years of life. Michael Schramme, DVM, MRCVS, PhD at the University of Lyon in France, deals with many DOD problems in young horses and advises horse breeders to try to diagnose and deal with these early on.
ANGULAR LIMB DEFORMITIES
When there is uneven pressure in the physis (the growth plate at the end of the bone), it is often due to physitis, and one side of the growth zone may stop growing while the other side continues to produce new cartilage and bone. This will result in angulation of the limb at the growth plate and it will not be growing straight.
The two most common abnormalities in this category are carpal valgus (the front leg is “in” at the knees) and fetlock varus (“out” at the fetlock joints). “Most of these angular limb deformities occur within the first few weeks
or months of life and will self-correct. The important thing with angular limb deformi- ties is not to miss the window of opportunity for treatment. This is limited by the growth potential remaining in the growth plate that’s affected,” he says. The potential for remaining growth disappears very quickly in the fetlock, compared to the carpus.
“With fetlock deformities you have to make sure you can correct them before the foal is two to three months old; the growth in this area has almost stopped by that age. With knees, however, you have much longer. The ideal time
for correction at the knee is around three to four months and preferably before eight or nine months, but with some young horses you may have up to 16 months sometimes. Although
the majority of longitudinal growth at the level of the knee occurs before eight months of age, there may be some growth left even up to 16 months,” explains Schramme.
“Abnormal cartilage and bone development are the cause of these conditions, but instead of cartilage in joints it is the cartilage in the growth plates at the ends of the long bones that’s affect- ed. In combination with some kind of trauma, this can make the limb grow at an angle.”
Physitis and angular limb deformities are similar in a way, because they affect the same areas--the growth plates of the cannon bone and the growth plates of the radius. “They are categorized as separate entities, but there can be a continuum between the two,” he says. “When the growth plate is affected by physitis, the cartilage thickens and fails to convert into bone. Such high pressures can build up in the growth plate, due to retention of uncalcified cartilage, that the ossification process stops. If that happens asymmetrically across the growth plate, such as on the inside or on the outside, the limb develops an angulation. One side ends up growing faster than the other and the limb becomes crooked.”
Treatments will vary, depending on the severity of the angulation and the window of op- portunity (relatively quickly for the fetlock and a little bit later for the knee, as previously men- tioned). Conservative treatment (confinement, reduction of growth rate, making sure the foal has a balanced ration, and corrective trimming of the feet to help keep the hoof properly bal-
DEVELOPMENTAL PROBLEMS IN YOUNG HORSES
Part Two: Angular Limb Deformities and Wobblers Part 1 appeared in our July 2020 issue. by Heather Smith Thomas
The three most common abnormalities in angular limb deformities are:
Carpal valgus, which is when the Carpal varus, when the front Fetlock varus, which is when a horse front leg is “in” at the knees. leg is “out” at the knees. is “out” at the fetlock joints.
86 SPEEDHORSE September 2020