Page 1085 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness in the Young Horse 1051

note of the age and exercise level of the foal to know
what the best treatment for correcting the laxity so
VetBooks.ir example, neonates are often very lax and require more
that a better evaluation of the ALD can be made. For
exercise, whereas older foals that have exercised rigor­
ously need to be stall confined for a few hours for the
laxity to improve. 4
If foals are examined on a regular basis, radiographs
are not necessarily required unless radical changes
have occurred between examinations. However, if it is
the first time the foal is examined for ALDs, especially
in older foals, radiographs provide the most conclu­
sive evidence about the location and potential cause of
the ALD. For ALDs, only dorsopalmar and lateral
radiographic views are required unless there is evi­
dence of problems within the joint, and then oblique
views should be added. The radiographs should be
centered over the joint of interest and include the mid‐
diaphysis of the proximal and distal long bones. These
views allow identification of the “pivot point” of the
ALD by drawing lines down the middle of the long
bones on the dorsopalmar view. 6,24,32 Where the lines
bisect is where the deformity is thought to originate
(Figure 5.4). In the case of asynchronous growth
across a distal physis, the deviation arises from the dis­
tal metaphyseal region rather than within the joint
(Figure 10.23A). Wedging of the epiphysis on the con­
cave side of the deviation, abnormal contour of the
cuboidal bones, and displacement of the splint bones
often accompany limb deviations of the carpus and
tarsus but usually resolve when the limb straightens
(Figure 10.23B). 6,22 Epiphyseal wedging is especially
prominent with varus deformities of the fetlock
(Figures 10.10 and 10.24), and collapse of the lateral
aspect of the third carpal bone is common with carpal
Figure 10.21. Foal with a combination of carpal valgus and valgus deformities (Figure 10.23B). However, severe
fetlock varus. Straightening the carpal valgus would probably make abnormalities such as physeal or cuboidal bone frac­
the fetlock varus worse and must be considered when developing a tures or crushing of the carpal or tarsal bones in con­
treatment plan. junction with an ALD are a major concern and may
contribute to permanent lameness problems, even if
the deviation is corrected.
Elevating or flexing the limb will often help allevi­
ate some of the perceptual problems that can be
encountered from rotation of the limb. Flexion of the TREATMENT
limb around the joint of interest allows the examiner
to compare the relative position of the distal limb to Treatment depends on the cause, location, and sever­
proximal limb by putting them in closer proximity to ity of the ALD, as well as the age of the foal. In general,
each other. In addition, it helps to distinguish some of varus deformities appear to be more problematic for
the more complicated cases in which there are ALDs future soundness than valgus deformities. Varus
involving both the carpus and fetlock. Picking up deformities of the fetlock (pigeon‐toed) are thought to
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and manipulating the limb in a medial‐to‐lateral direc­ contribute to pastern and fetlock lameness problems,
tion also allows the examiner to determine whether whereas mild carpal valgus was found to be protective
the limb can be manually straightened or not. If the for carpal injuries in racing Thoroughbreds. Most foals
3
limb can be manually straightened, it is highly likely have a mild degree of carpal valgus conformation
that the deformity is centered within the joint and (approximately 5°) that tends to decrease as they grow
results from delayed ossification of the cuboidal bones older. 16,28 Foals tend to grow into the mild carpal valgus
or laxity of the periarticular soft tissues. If the limb as the chest expands during growth. 16,32 If the limb is
cannot be straightened, the deformity likely originates completely straight as a foal, a carpal varus may develop
at the physeal region. Watching the foal walk is often as the chest expands during growth. In contrast, fetlock
very useful in distinguishing how much of the ALD is varus deviations tend to worsen with age up to 6
a component of ligamentous laxity. Ligamentous lax­ months. Therefore, mild carpal valgus deformities
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ity will tend to show more exaggerated movements should not be treated, whereas minor varus deformities
around the joints of interest, making the ALD more of the fetlock probably should be addressed because of
pronounced. In these foals, it is important to make the potential to worsen with age.