Page 541 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Distal Limb 507

position of the distal phalanx within the hoof capsule is Casting and Splinting
considered because it is natural to try and restore the Casting the distal limb is beneficial in horses with
VetBooks.ir the stresses within the lamellae suggests that restoring acute and early chronic laminitis but is particularly valu-
alignment of the DIP joint. However, consideration of
able in the treatment of chronic cases with unilateral
the symmetry of the DIP joint is likely to be counterpro-
ductive. Unilateral distal displacement frequently occurs complications such as subsolar abscessation (Figure 4.82).
with some rotation, in which circumstances heel eleva- Half‐limb casts, half‐limb casts with transfixation pins,
6
tion may also be warranted. While this technique has and open soled half‐limb casts have been used. However,
been beneficial in some horses, more experience is foot or pastern casts may also provide some stability to
11
required before firm recommendations are possible. the lamellae. If fit snugly at the proximal end of the
metacarpus, the half‐limb casts potentially offer some
weight sparing by the digit. However, transfixation pin
casts are likely to provide dramatically greater load spar-
ing by the foot. Additionally, by decreasing movement
within the distal limb, casts may decrease the pain as the
horse moves around a stall. Open soled casts offer the
advantage that the ground surface of the foot can be
inspected and treated while the foot is in the cast and
that load bearing by the ground surface of the foot may
be more selectively applied using synthetic polymers. If
casts are only placed on one limb, it is important to place
some type of support on the contralateral limb to both
support the foot (which is usually also affected with
chronic laminitis) and equalize the height of the two
limbs. Splints offer some of the advantages of immobili-
zation, but offer no relief from load bearing.

Deep Digital Flexor Tenotomy
Tenotomy of the DDFT abolishes or greatly reduces or
abolishes the flexor moment about the DIP joint. The
direct result is that the center of pressure should move in a
palmar direction to a point directly distal to the center of
rotation of the DIP joint. The benefits are that it decreases
the tension within the dorsal lamellae and compression on
the dorsal sole, thus allowing realignment of the distal
phalanx with the ground without exacerbating the delete-
Figure 4.81. This horse has medial asymmetrical distal rious forces on the dorsal lamellae and sole (Figure 4.82B
displacement, evidenced by disparate growth of the medial and and C). This is usually accompanied by decreased pain
lateral walls. A wooden shoe has been positioned to act as a lateral and increased sole growth dorsally. The disadvantages are
extension to increase weight‐bearing by the healthier lateral side of that the toe of the foot may become elevated from the
the foot to decrease pain from compression of the sole and tension ground as the horse rocks back or ambulates and that
in the lamellae medially. Source: Courtesy Dr. Stephen O’Grady. mild to moderate subluxation may occur in the DIP joint

A B C D

Figure 4.82. Tenotomy of the DDFT is most commonly performed characterized by dorsal displacement of the extensor process of the
standing at the mid‐cannon region using a guarded bistoury (A). The distal phalanx away from middle phalanx (arrow) and by caudal
tenotomy allows realignment of the rotated distal phalanx (B) with the displacement of the distal articular surface of the middle phalanx so
ground surface (note realignment of the foot in C after 6 weeks). that a line bisecting the middle and proximal phalanges does not bisect
Subluxation of the DIP can occur following the procedure (D), the middle of the articular surface of the distal phalanx (black line).