Page 112 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.3 The foot 87

VetBooks.ir where the heel bulbs and heel buttresses are closer the hoof may be an incidental finding in lameness
Contracted heels are described as the condition
examinations.
together than normal. It is invariably associated with
a narrow frog, and frequently with high or underrun Differential diagnosis
heels. The condition is thought to occur secondary Any chronic lameness originating within the foot;
to heel pain, reduced weight bearing by the heels, healed traumatic hoof wounds.
and subsequent reduced expansion of the heels dur-
ing the normal cycle of the stride. Diagnosis
Underrun heels occur when the heels are more Diagnosis of imbalance and poor conformation of
acutely angled to the ground than normal, and usu- the hoof and distal limb is made by careful visual
ally occur in horses with excessive length of toe. inspection and measurement (Fig. 1.149). Any
Typically, the heels are longer than normal and changes observed reflect movement of the coro-
they may be curved dorsally and axially so that the nary band, distortion of the hoof wall and change
weight-bearing surface of the heels is displaced dor- in the spacing of the growth rings. The distal limb
sal to the base of the frog. The foot–pastern axis is should be examined with the foot both on and off
usually broken back. While the aetiology has not the ground. When observed on the ground, the
been definitively determined, it appears that some ground surface of the foot should be approximately
breeds, particularly Thoroughbreds, are genetically perpendicular to the axis of the limb. When the
predisposed. In other instances, trimming practices foot is observed off the ground, typically with the
that result in excessive length of heel or shoeing
practice that causes excessive weight bearing on the
heels encourage the heels to become underrun. An 1.149
upright foot with high heels usually accompanies
either contracted heels or a flexural deformity of
the DIP joint. However, in the latter, in contrast to
the former, the heels are frequently widely spaced.
Upright heels are frequently associated with a bro-
ken forward foot–pastern axis. When a horse has
one upright foot with contracted heels, the contra-
lateral foot often has low/underrun heels.
Sheared heel is a condition in which one heel
bulb of the foot is displaced proximally compared
with the other. While the condition is called
sheared heel(s), the proximal displacement of the
coronary band frequently begins in the quarter, so
it might be more appropriately termed sheared heel
and quarter. This condition is often associated with
contracted heels. The exact cause of sheared heels is
undetermined, although it is thought to be second-
ary to inappropriate trimming prior to shoeing in
many horses. Sheared heels may be associated with
lameness that is abolished with a palmar digital
nerve block.
Fig. 1.149 View from the front of a foot with
Clinical presentation chronic mediolateral imbalance. Note the sloping
Horses with hoof imbalance frequently present with coronary band, asymmetrical walls and obvious flaring
lameness, although abnormal shape or movement of of the medial wall.