Page 74 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.2 The foal and developing animal 49

VetBooks.ir ACQUIRED MUSCULOSKELETAL ABNORMALITIES

ACQUIRED ANGULAR LIMB DEFORMITIES
Asymmetric or imbalanced longitudinal bone
growth occurs from a distal physis or epiphysis due
Definition/overview to overload of the physis on one side, leading to
Acquired ALDs usually manifest as a lateral or decreased growth on that side (e.g. greater growth
medial deviation to the long axis of the limb in the from the medial distal radial physis compared with
frontal or transverse plane, commonly seen at the the lateral physis leads to carpal valgus). Direct
carpus, fetlock and tarsus. They are more com- trauma to the physis can also lead to asymmetric
mon in the forelimb and can be uni- or bilateral. damage and subsequent growth.
There is no sex predisposition. Lateral deviations
are termed valgus and medial deviations are termed Clinical presentation
varus. Many ALDs are associated with postural The history of a developing ALD is in two main peri-
or rotational deformities, especially with carpal ods: birth to 6–8 weeks of age and 6 weeks to 9 months
valgus, when a lateral rotation is common. ALDs of age. All breeds are affected, but it is particularly
can be congenital (see Congenital musculoskeletal common in fast growing larger breeds. Deformities
abnormalities, p. 34) or acquired/developmental are more common in the forelimb. Other types of
(see below). DOD may be present.
The foal should be examined at rest and walk-
Aetiology/pathophysiology ing. The site(s) and degree of angulation of affected
The aetiology is multifactorial and includes genet- joint(s) are assessed in the forelimbs from in front and
ics, fast growth rate and/or excessive body weight, in the hindlimbs from behind, with the foal standing
over- or undernutrition, mineral and trace element as square as possible with the foot directly under the
imbalances, excessive exercise, internal or external upper part of the limb. It is important that concur-
trauma and contralateral limb lameness. These fac- rent rotation from the chest is taken into account for
tors, either individually or in combination, contrib- forelimb evaluation by viewing the limb perpendicu-
ute to the development of acquired ALDs. lar to the frontal plane of the limb (Figs. 1.88, 1.89).

1.88 1.89

Fig. 1.88 Bilateral acquired carpal valgus angular
limb deformity. In this detailed view of the left Fig. 1.89 Left forelimb fetlock varus deformity.
forelimb, note the severe valgus deformity and
enlarged distal radial physis.