Page 563 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Distal Limb 529

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A B

Figure 4.109. Lateral (A) and dorsoplantar radiographs (B) of a nondisplaced, moderately comminuted P1 fracture that was repaired with
multiple lag screws placed through stab incisions.

Clinical Signs fracture configuration with comminuted fractures as well

The clinical signs associated with P1 fractures are as the presence or absence of joint involvement.
Midsagittal fractures are often readily apparent on
variable and depend on the fracture type and degree of the DP view, but some short, incomplete fractures may
fracture propagation. In most cases there is usually a be difficult to see radiographically. In addition, multiple
history of an acute onset of lameness. Horses with fracture lines on a single radiographic view do not
incomplete sagittal fractures may demonstrate moderate always indicate more than one fracture because of the
pain and lameness initially, but it may be of a short spiral nature of these fractures. This occurs because
duration. However, fetlock effusion is usually present, the fracture lines are not completely superimposed on
and a painful response is often elicited with flexion and the radiographic view.
rotation of the phalanges. Horses with complete sagit- Some P1 fractures may also be misdiagnosed as the
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tal fractures are usually quite lame (grade 3–4 of 5), and nutrient foramen, especially in Standardbreds. In
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fetlock effusion and swelling of the pastern region is horses with comminuted P1 fractures, the presence or
usually apparent. Horses with comminuted fractures are absence of an intact bony strut that spans from the
usually non‐weight bearing and may show signs of MCP/MTP to the PIP joints is one of the most important
physical distress such as sweating. The pastern region is radiographic features. In addition, the degree of fracture
often obviously swollen, and crepitus and instability is displacement, the presence of comminution at the joint
palpable. surfaces, and whether the fracture involves the PIP joint
Adequate external immobilization of the fracture in are all important radiographic features that may affect
these horses is mandatory if they are being transported treatment. Similar to comminuted P2 fractures, CT can
for surgical repair. Perineural anesthesia is usually be very beneficial to more accurately assess the degree of
unnecessary to make the diagnosis, but some horses comminution of P1 fractures and to aid in preoperative
with short sagittal P1 fractures may present for a rou- planning for surgery.
tine lameness evaluation. Perineural anesthesia is con-
traindicated if any type of P1 fracture is suspected
because it will increase the risk of fracture propaga- Treatment
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tion. Guidelines for transporting horses with commi- Noncomminuted P1 Fractures
nuted P1 fractures can be found in Chapter 12.
The decision on how to treat horses with noncom-
Diagnosis minuted fractures usually depends on the fracture type,
fracture location and length, degree of displacement,
Radiographs are required to characterize the type of P1 and intended use of the horse. Treatment options include
fracture and dictate the appropriate treatment. The radio- confinement with bandaging, confinement with a distal
graphic examination should include at least four views: limb cast, internal fixation with lag screws and/or bone
DP, LM, DLPMO, and DMPLO. Additional views at vary- plates, external skeletal fixation alone, or internal
ing angles may be necessary to accurately document the fixation combined with external skeletal fixation.