Page 632 - Adams and Stashak's Lameness in Horses, 7th Edition

598 Chapter 5

Angular and flexural deformities are usually pathologic
in origin and often require prompt therapy. However,
VetBooks.ir origin often occurs proximal to the carpus. In those
rotational deformities are often conformational, and the
foals in which angular and flexural deformities are
deemed to be of clinical significance, prompt therapy is
needed to prevent lameness and loss of future athletic
performance.
A study of three breeds of French horses (Thoroughbred,
trotters, and Selle Français) showed that carpal valgus
was the most frequent congenital abnormality (found in
42.1% of foals) and that carpal contracture occurred in
30.8% of foals. During the study conformation
became less valgus and most issues resolved by the time
of weaning. 101

Angular Limb Deformity
ALD in general are discussed in Chapter 10, but more
detail is provided here on ALD of the carpus. ALD of the
carpus are one of the most commonly treated problems
in equine practice. However, mistakes are often
made using both overconservative and overaggressive
approaches to treatment. An understanding of the
normal developmental patterns of the limbs is essential
to avoid these mistakes.

Figure 5.1. Normal left bony carpus. The joints (from proximal to Etiology
distal) are the antebrachiocarpal (radiocarpal), middle carpal ALD of the carpus can result from asymmetric growth
(intercarpal), and carpometacarpal joints. Arrows, areas where chip in the distal radial metaphysis, asymmetric growth of
fractures may occur on the radius; M, medial; L, lateral; R, radial the distal radial epiphysis, incomplete ossification of the
carpal bone; I, intermediate carpal bone; U, ulnar carpal bone; 3rd, cuboidal bones or the proximal aspect of the second and
third carpal bone; 4th, fourth carpal bone.
fourth metacarpal bones, and/or joint laxity. ALD are
typically congenital or acquired. Congenital abnormali-
ties such as incomplete ossification of the cuboidal
DEVELOPMENTAL ABNORMALITIES bones and collateral ligament laxity are not uncommon.
OF THE CARPUS Uterine malpositioning or stagnant movement can lead
to decreased growth, which can be correlated with mare
Developmental abnormalities of the carpus are one of 77
the most common problems at birth in young horses. nutritional status. Cuboidal bone ossification is typi-
cally complete by the time of foaling, but without
82
The types of developmental problems can be classified complete ossification, normal loading (weight‐bearing)
into three categories:
within the joints can cause progressive damage to the
1. Angular limb deformities (ALD) or deviation in the cartilaginous structure, predominately on the lateral
frontal plane is defined by the joint and/or bone at side of the joints leading to progressive valgus deformity.
the center of the deviation and further defined by the Toxic chemicals and other possible endocrine influences
placement of the distal limb in reference to that have also been linked to congenital ALD. 3,39,50,83
13
center. For instance, in the carpus, the distal limb is Some foals are born somewhat dysmature and may
medial to the carpus in foals that have carpal varus, have joint laxity in the carpus. Constant monitoring and
and the distal limb is lateral to the carpus in those reassessment of these cases are necessary. Oftentimes the
that have carpal valgus. It should be noted that most stress of turnout or small pen exercise is enough to
foals are born slightly carpal valgus because there is strengthen those tissues and self‐correct the problem.
greater musculature on the lateral aspect of the distal However, in these individuals, care must be taken to
radius compared with the medial, thus providing avoid excessive exercise, which could lead to progressive
increased tension across the carpus on the lateral side ALD. In these latter cases, progressive laxity can lead to
of the limb. However, with birth and growth, this pathologic stress levels within the carpal bones, possibly
usually self‐resolves to a normally straight limb. leading to carpal bone malformation. Carpal deformity
2. Flexural deformities are defined as deviations in the should be evaluated before turnout and then again after
sagittal plane of the knee so that the joint of refer- a determined amount of time (1–2 hours). If the deform-
ence is cranial or caudal to a line drawn down the ity is slightly worse after turnout, but returns to baseline
center of the limb from the lateral side. 13 throughout the day, then the amount of turnout can be
3. Rotational deformities occur when the limb distal to adjusted to help the foal adapt and self‐correct.
the point of origin rotates outward or inward from Foals that have acquired ALD are usually born
the normal axis. 13 normal, but the limb starts to deviate with time. This can