Page 637 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 603

stimulate growth correction, although it is reserved for
foals older than 3–4 months of age to avoid problems
VetBooks.ir bridging is thought to occur, the physis can be resected
with fetlock ALD.
In addition to fixation, in severe cases in which bone
and fat graft interposed to keep the physis open. 43

Prognosis
The prognosis is good to excellent in more than 80%
of the cases. 4,14,15,40 However, Mitten et al. found that in
199 racehorses, there was no significant difference in the
ability to start. Foals that had periosteal transection
experienced a slight decrease in the percentage of starts,
a slight decrease in the number of 2‐year‐old starts, and
a slight decrease in the starts percentile ranking number
compared with a nontreated group. Although the limbs
were deemed to be straight, the investigator concluded
that other factors in the carpus could have led to these
reduced outcome parameters in cases treated with peri-
osteal transection. There is concern that significant
86
ALD of the carpus could lead to subtle but permanent
deformity within the carpal bones. This could theoreti-
cally lead to abnormal forces within the carpus, which is
another reason to address these promptly.

Flexural Deformity
Flexural deformity, commonly known as bucked
13
knees, is thought by some to occur in 3%–4% of foals.
While mild cases are typically uneventful (Figure 5.6),
severe cases can result in dystocia during birth. The
deformities, characterized by a disparity in length
between the muscle tendon unit and bone, can be con-
genital or acquired. Acquired deformities occur between Figure 5.6. A foal with mild flexural deformity of the carpi that
1 and 6 months of age. did not require treatment because it self‐corrected over a few days.
hours of rest. In addition, rupture of the common digital
Etiology
extensor tendon can lead to flexural deformity; how-
The pathogenesis of flexural deformity is unknown. ever, it is unknown whether the rupture causes the
Autosomal trisomy in two foals has been associated deformity or vice versa.
21
with this problem. It has been hypothesized that the
more common congenital occurrences are due to uterine Clinical Signs
malpositioning; poor mare nutrition; exposure of the
mare to influenza, Sudan grass, locoweed, or other The degree of flexural deformity is variable and usu-
agents; and trauma to the limb, in which increased ally involves both front limbs. In mild cases it may only
flexor tone and decreased extensor tone are noted. 78,79 occur after turnout or when the foal is newborn. In these
Acquired flexural deformity can be induced by rapid cases improvement usually occurs within days, with or
growth, overnutrition, pain in the limb, or pain in other without rest. In foals with significant flexural deformity,
limbs that causes overloading of that particular limb. the gait is often significantly affected, and it becomes
Rapid growth is thought to induce physeal pain, and very difficult for the foal to move around. In addition,
consequently some of these foals stand with their carpi the fetlock joint may become involved in the deformity
flexed to relieve the pain. In addition, damage to the and make it difficult for the foal to rise. It is not uncom-
suspensory ligament, superficial digital flexor tendon mon to see skin trauma to the fetlock in these foals.
(SDFT), or deep digital flexor tendon (DDFT), or injury
to the heel or carpal pain can cause the foal to rest the Diagnostic Imaging
limb in a flexed fashion, leading to contracture of those
tissues. Radiographs should be taken in cases that are deemed
It is not uncommon to see mild flexural deformity in to be clinically significant. Lateromedial and dorso-
foals that have been turned out soon after birth. In these palmar views are needed to assess for incomplete ossifi-
cases it is thought that the normal exercise, especially in cation of the bones, cuboidal bone malformation, or
those foals that may be slightly dysmature, can lead to damage in the carpus. A complete series of radiographs
microdamage within the physes and consequently pain. should be taken if abnormalities are detected on initial
This tends to improve on its own within a couple of views.