Page 103 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

78 CHAPTER 1

VetBooks.ir trimming. Moreover, hoof cracks are more likely to at the coronary band or cracks in the bars. Occult
hoof cracks at the coronary band may be tentatively
occur if there is prior disease affecting the shape or
mechanical properties of the hoof wall (e.g. lamini-
there is an associated hoof imbalance. A definitive
tis). Hoof cracks are classified by location, depth and identified based on pain on palpation, particularly if
whether they are complete or incomplete. They may diagnosis is possible when it breaks through to the
occur at any point around the circumference of the surface of the hoof. Foot radiographs may reveal
hoof wall, including the bars. Partial- and full-thick- changes in the distal phalanx associated with chronic
ness cracks extend through part of, or the entire cases (Fig. 1.130). Application of hoof testers may
thickness of, the hoof capsule, respectively. Blind both reveal occult hoof cracks, particularly those in
hoof cracks that start deeper in the hoof capsule the bars, and indicate if they are a source of pain.
occur occasionally. Complete hoof cracks extend
from the weight-bearing surface of the wall to the Management
coronary band, whereas incomplete hoof cracks start Not all hoof cracks need treatment. The nature of the
either proximally or distally, but do not extend the crack and its relationship to hoof balance and prior
full length of the wall. Toe cracks most frequently trauma should be determined. The movement of toe
start at the ground surface, whereas quarter cracks cracks varies with conformation and as the animal
are more likely to start at the coronary band. Hoof moves. Toe cracks have a tendency to compress with
cracks become painful when they either are unstable weight bearing, particularly if the toe is short and
and pinch the underlying tissues or become infected. squared off. The treatment depends on the nature
Quarter cracks are more likely to be full thickness or of the crack and the exercise expected of the horse
become infected than toe cracks. in the future. If rest from exercise is possible, most
Horizontal hoof cracks are less common than hoof cracks that are related to hoof imbalance will
vertical hoof cracks. They may spread around a vari- respond to corrective trimming to restore the opti-
able amount of the circumference of the hoof wall. mal balance with or without shoeing, and the crack
They most commonly occur following abscesses will grow out (Figs. 1.131, 1.132). For those horses
that drain at the coronary band. Much less com- that have to perform in the near future, a crack may
mon, but more severe, are horizontal fissures caused need to be stabilised. Prior to stabilisation the crack
by selenium toxicity, which are likely to extend must be debrided to ensure no foreign, infected or
around a greater part of the circumference and to necrotic tissue is entrapped. Stabilisation should pre-
cause lameness. vent both compression and expansion of the crack and
is usually performed with synthetic polymer patches
Clinical presentation that incorporate sutures such as Kevlar or steel, with
The majority of hoof cracks are present on visual or without sheet metal screws (Figs. 1.133, 1.134).
examination. Not all cracks are clinically signifi- The horse is then shod. Infected cracks must be fully
cant, and regional and intrasynovial analgesia may exposed and cannot be completely covered, although
be used to differentiate the cause of any lameness a patch may be placed over a drain through which an
present. Lameness is usually associated with infec- antiseptic can be flushed. Cracks that follow coro-
tion or hoof instability. Hoof testers can be used to nary band trauma are unlikely to grow out and must
assess instability and pain, and to increase visibility be managed indefinitely. Cracks associated with
of purulent or bloody discharges. laminitis may respond to therapeutic shoeing for the
primary disease, depending on the residual level of
Differential diagnosis lamellar damage and stability/shape of the overlying
None. hoof capsule.

Diagnosis Prognosis
Most hoof cracks are obvious (Fig. 1.129), but careful The prognosis varies with location, depth, bal-
inspection may be necessary to identify small cracks ance of the foot and the presence of other disease.