Page 100 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.3 The foot 75

VetBooks.ir deformable surface or shoe equivalent is the best way of the lameness, the degree of flexion of the DIP
joint (phalangeal rotation) and the thickness of the
to improve its comfort but it does not ensure that
the distal phalanx can be stabilised. If shod, these
also been used to predict the likelihood of survival
horses benefit from moving the point of breakover sole. The severity of rotation of the hoof capsule has
in a palmar direction and by variable support of the but is probably more useful in predicting the likeli-
ground surface of the foot, depending on the sen- hood that the horse will need indefinite therapeutic
sitivity of the sole. Wooden shoes are a reasonable hoof care.
starting point but may be insufficient if displacement
continues. If the sole of the foot makes contact with WHITE LINE DISEASE
the surface of the wood and compresses the underly-
ing soft tissues, a significant increase in pain can be Definition/overview
expected. For horses that fail to respond, encasing White line disease is a keratolytic syndrome of the
the foot in a phalangeal cast, with a rounded bottom, deeper layers of the stratum medium of the hoof wall.
may provide comfort and ease of movement.
Horses that sink asymmetrically constitute a Aetiology/pathophysiology
third treatment scenario. As with horses that dis- White line disease should be considered a syndrome
place distally symmetrically, there is no rotation of rather than a disease because, while it is considered to
the distal phalanx about the DIP joint to counter- be infectious, the cause is unknown and both fungi
act. However, in contrast to horses with symmetrical and anaerobic bacteria have been implicated. The
distal displacement, horses with asymmetrical distal keratolytic process forms cavities within the hoof
displacement do have less damaged lamellae on the wall containing air and moist degenerating horn.
contralateral side to that which has displaced. Again, Usually only one foot is affected, but multiple foot
these horses benefit from enhanced breakover, cases do occur. The lesions are not associated with
and in addition, they benefit from moving weight inflammation of the underlying tissues. If enough
bearing towards the less affected side. This can be of the wall is affected, the distal phalanx is no lon-
accomplished by various means, but most easily by ger adequately supported by the outer layers of the
extending the shoe out further on the unaffected hoof wall, and it displaces. Subsequent pressure on
side as an extension. This is readily accomplished the sole may cause bruising and lameness of variable
with a wooden shoe. magnitude.

Prognosis Clinical presentation
The prognosis for horses with laminitis is varied Early white line disease is often asymptomatic and
based on both the type of displacement that has only identified incidentally by the farrier when the
occurred, the severity of the initial disease/symp- foot is trimmed. It is seen as a discoloured area or
toms and the relative stability of the distal phalanx defect in the inner layers of the stratum medium
within the hoof capsule at the time of diagnosis. on the ground surface of the wall. Alternatively, the
Overall in chronic laminitis, if caught early in the horse presents with lameness associated with dis-
disease process and treated appropriately, the prog- placement of the distal phalanx and bruising. The
nosis is guarded. The prognosis is best for horses sole may appear flattened and show the character-
with minimal rotation, more guarded with rotation istic discolouration associated with bruising. The
and worst for horses with symmetrical sinking. For hoof feels warm and application of hoof testers to
horses with severe acute laminitis, the prognosis the sole elicits a withdrawal response. The cavita-
should always be guarded to poor because the course tion in the wall may cause the wall superficial to the
of the disease is highly unpredictable. The likeli- lesion to bulge out from the normal contour of the
hood of survival and return to function is best corre- wall (Fig. 1.125).
lated against the severity of the initial clinical signs.
The prognosis for survival in horses with chronic Differential diagnosis
rotation is probably best correlated with the severity Laminitis; abscess.