Page 560 - Adams and Stashak's Lameness in Horses, 7th Edition

526 Chapter 4

aspects of P1 are types of noncomminuted fractures and a. Distal joint fractures: Involve the PIP joint
are discussed in the fetlock section. Fracture configura- b. Palmar/plantar eminence fractures: Involve the
VetBooks.ir from small fissures that enter the metacarpophalangeal/ c. Physeal fractures: Usually Salter–Harris type II
MTP/MCP joint (Figure 4.107)
tions (excluding osteochondral fragmentation) range
d. Oblique or transverse diaphyseal fractures
metatarsophalangeal [MCP/MTP] joint to highly com-
minuted fractures (“bag of ice”) that affect both cortices Comminuted P1 fractures can range from fairly sim-
and the proximal and distal joint surfaces. Stress or
fatigue‐type fractures that may not be identified on rou- ple three‐piece fractures to the bag of ice type of injury
(Figures 4.108 and 4.109). However, a variety of con-
tine radiographs may also occur in performance horses.
Most P1 fractures are closed, although 8 of 64 commi- figurations of comminuted P1 fractures is possible. For
treatment purposes, they are divided into fractures that
nuted fractures were open at the time of presentation and
an additional 4 had extensive bruising with serous fluid have an intact cortex (strut) of P1 from the proximal to
distal joint surfaces (moderately comminuted) and frac-
oozing through intact skin in a retrospective review. 32
Noncomminuted P1 fractures have been classified tures that do not have an intact bone strut (severely
32,40
into several types: comminuted). Less common types of P1 fractures
include proximal medial collateral ligament avulsion
1. Midsagittal or sagittal fractures: Exist primarily in fractures, dorsal nonarticular fractures, and stress or
the sagittal plane and begin at the proximal articular fatigue fractures. Stress‐ or fatigue‐type fractures may
surface precede sagittal or comminuted P1 fractures and occur
a. Short (extend less than 30 mm in length distally; almost exclusively in performance horses. Medial
Figure 4.104A) collateral ligament avulsion fractures are discussed in
b. Long (extend more than 30 mm in length distally; the fetlock section.
Figure 4.104B) Sagittal P1 fractures occur most commonly and may
c. Complete (exit the lateral cortex or span both be present in the contralateral limb in a small percentage
joint surfaces; Figure 4.105) of the cases. 17,38,69 Sagittal and other types of noncom-
2. Dorsal frontal fractures: Begin at the MCP/MTP minuted P1 fractures are primarily seen in racing
joint in the frontal plane and extend to the dorsal Thoroughbreds and Standardbreds but can also occur in
cortex or distally toward the PIP joint; can be incom- other types of performance horses. They often affect
plete or complete (Figure 4.106) the hindlimbs in Standardbreds and the forelimbs in

A B

Figure 4.104. Dorsopalmar radiographs of the pastern region revealing short (A) and long (B) incomplete sagittal fractures of P1 (arrows).
The fracture in (B) was repaired with two lag screws through stab incisions (Figure 4.110).