Page 556 - Adams and Stashak's Lameness in Horses, 7th Edition

522 Chapter 4

for return to use in horses with luxations/subluxations
treated early by arthrodesis in which good reduction
VetBooks.ir Convalescence is similar to that of other conditions that
and stabilization of the PIP joint was achieved.
1,26,31,41,67
require a PIP joint arthrodesis, and up to a year may be
required before the horse may return to performance.
Three cases of bilateral acquired pelvic limb intermittent
dorsal subluxation treated by tendonectomy of the
medial head of the DDFT responded favorably to the
treatment and the subluxation resolved between 1 and
7 days postoperatively. The authors have no experi-
63
ence with this particular surgical technique.

FRACTURES OF THE MIDDLE (SECOND)
PHALANX (P2)
Fractures of P2 occur most commonly in the hindlimbs
of middle‐aged western performance horses used for cut-
ting, roping, barrel racing, pole bending, and reining. 8,10,42
However, these fractures may occur in any horse during
lunging, turnout, after kicks or falls, or any form of sin-
gle‐event trauma. Fractures of P2 can also be seen in Figure 4.100. Oblique radiograph of the pastern region
foals and usually involve the proximal physis, resulting demonstrating a medial plantar eminence fracture of P2. This horse
in subluxation of the PIP joint. Although the fracture is presented for a hindlimb lameness of 2 weeks’ duration.
12
common in Quarter horses, any breed can be affected.
Based on retrospective studies, the Quarter horse repre-
sents approximately 50% of the breeds affected, Western
stock is the most common activity contributing to the
injury, and the hindlimbs are affected approximately
three times more frequently than the forelimbs. 8,10,42
A variety of fracture types involving P2 have been
reported, including osteochondral (chip) fractures,
palmar/plantar eminence fractures, axial fractures,
and comminuted fractures. 5,8,10,29,31,35,41,46,52,60,70,72
Osteochondral fractures and axial fractures are rare,
whereas eminence and comminuted fractures occur
commonly. Thoroughbred and Standardbred racehorses
and hunter/jumper horses appear to be at increased risk
for osteochondral fractures involving the PIP joint.
70
The fracture can either be located dorsally (most com-
mon) or on the palmar/plantar aspect lateral or medial
to the midline. 46,52,60 Palmar/plantar fractures do not
typically involve the attachments of the DSL or the
branches of SDFT. Some of these osteochondral frag-
ments may be seen in young horses and may be develop-
52
mental in origin. Occasionally, multiple fragments may
occur on the proximal palmar/plantar aspect of P2 that
appear to be avulsion fractures. Despite the size of the
fragments, the development of secondary OA appears
slow, but removal is usually recommended.
Radiographic examination of the opposite PIP joint Figure 4.101. Lateral radiograph of the pastern demonstrating
should be done because palmar/plantar fractures have biaxial eminence fractures of P2. Internal fixation is required for
these types of fractures to prevent palmar/plantar luxation of P1.
been reported to occur bilaterally. Osteochondral frac-
46
tures of P2 involving the DIP joint are uncommon and
may be caused by use‐related trauma or direct trauma Simple axial fractures of P2 occur rarely. A misdi-
63
from a penetrating injury. 70,72 Palmar/plantar eminence agnosis of this fracture can easily be made if the cen-
fractures involving the PIP joint occur frequently. They tral sulcus of the frog is prominent and it is filled
can either be uniaxial (involving one eminence; inadequately with packing material prior to the radio-
Figure 4.100) or biaxial (involving both eminences; graphic exam. The fracture should be visible on at
Figure 4.101). Uniaxial eminence fractures do not result least two radiographic views to make a definitive diag-
in subluxation of the PIP joint, whereas biaxial fractures nosis. This type of fracture may progress to a commi-
can contribute to subluxation or complete luxation of nuted fracture under appropriate biomechanical
the joint (Figure 4.102). factors.