Page 61 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

36 CHAPTER 1

VetBooks.ir DEFECTIVE OSSIFICATION OF dorsopalmarly/ dorsoplantarly and mediolaterally,
THE CUBOIDAL BONES OF THE
particularly if joint laxity is also present. Radiographs
CARPUS AND TARSUS
can reveal one or more abnormal carpal bones, but
it is not possible to fully interpret the amount of
Defects in the ossification process can occur in any cartilage precursor damage (Fig. 1.63). Full ossifi-
young foal, but premature and dysmature foals are cation of these bones occurs at about 30 days and a
most commonly affected. Fetal growth retardation more accurate prognosis can be given at this stage.
due to placental disease, severe metabolic or para- Secondary degenerative joint disease (DJD) is a pos-
sitic disease in the mare, twin pregnancy or poor sible sequela. Treatment should involve support of
mare nutrition may be involved. Carpal valgus is the limb in correct axial alignment and prevention of
the most common presentation at birth; this either crushing of the cartilaginous precursors of the ossi-
remains static or worsens over the first 2 weeks of fied cuboidal bones in a tube cast. It is important to
life due to exercise deforming the soft cartilage monitor such casts as skin damage in foals of this age
structures. Clinical examination reveals no pain from pressure sores is a high risk. Thus changing
or swelling in the affected joint initially, and usu- the cast every 3–4 days is important. Another form
ally no lameness is present. An increased range of of cuboidal bone defective ossification is the col-
movement within the joint may be present both lapse of the third and/or central tarsal bone(s). This
condition is usually bilateral and affected foals may
present with excessive flexion of the hocks (‘curby’
conformation) leading to a characteristic bunny-hop
1.63 gait (Fig. 1.64). Tarsal valgus may also be present
(Fig. 1.65). Radiography reveals wedging of the cen-
tral and third tarsal bones (Fig. 1.66). Treatment is
similar to cases of joint laxity to allow ossification to
progress. DJD is a possible sequela.

1.64

Fig. 1.63 Dorsopalmar radiograph of the left Fig. 1.64 Three-week-old Warmblood foal with
forelimb carpus of a neonatal foal showing evidence partial collapse of the small tarsal bones in a dorsal
of carpal bone hypoplasia. Note the rounded profile of plantar plane, leading to a ‘curby hock’ appearance
the individual carpal bones with apparently increased (arrow). (Plantar aspect from point of hock to plantar
space between them due to incomplete ossification of fetlock is not straight.)
the cartilage surrounding the centres of ossification.