Page 986 - Adams and Stashak's Lameness in Horses, 7th Edition

952 Chapter 9

cause. Fractures may not be apparent on radiographs markable, whereas ultrasonography confirms increased
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until 7–10 days after they occur. Conventional manage­ joint fluid and mild thickening or proliferation of the
VetBooks.ir for 8–12 weeks. If lameness is still evident it is common hydrotherapy, poultice, and bandaging. Joint injection
synovium. Treatment includes local therapy with ice,
ment includes rest with a bar shoe with or without clips
to perform a palmar digital neurectomy; however, some
with chondroprotective agents and corticosteroids or
racing jurisdictions do not allow the horse to race fol­ IRAP is common. Systemic nonsteroidal anti‐inflamma­
lowing this procedure. There is usually a good prognosis tory drugs (NSAIDs) are also frequently administered.
for return to racing, even though there is commonly evi­ Common areas of cartilage and osteochondral trauma
dence of osteoarthritis (OA) or a step defect once heal­ involve the dorsal rim of P1, usually medially or less
ing is complete. Unfortunately, horses with type III commonly medially and laterally. This is believed to
coffin bone fractures with significant displacement or occur from the repetitive trauma and wear of the rim
fractures of the navicular bone have a poor prognosis to against the distal metacarpus and is the most common
return to racing. area for development of chip fractures in the fetlock.
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Usually there are joint effusion, warmth, and varying
degrees of pain on flexion, along with focally sensitive
Pastern
palpation on the area of the rim that is involved.
Lameness associated with the pastern region is rela­ Lameness is usually only transient if present at all, unless
tively uncommon, but fractures of the proximal phalanx advanced changes have occurred in the joint. Often
(P1) occur frequently. The most commonly reported there is a reduction in performance rather than an overt
fracture configuration is parasagittal, extending distally lameness. The prognosis is good with arthroscopic
from the sagittal groove of the proximal articular sur­ removal of dorsal P1 chip fractures in racehorses as long
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face of the bone. As the fracture courses distally, it most as appropriate convalescence is allowed. Recuperation
commonly diverges laterally before either exiting the lat­ time averages 2 months or longer. Reports indicate that
eral cortex of the bone or spiraling into an oblique (dor­ there is no difference in prognosis with different sizes of
solateral/palmar/plantaromedial) plane approaching the fragments, but larger fragments usually induce more
distal epiphysis and proximal interphalangeal joint. cartilage damage and wear on the distal metacarpus,
Long (>30 mm) incomplete parasagittal fractures are the especially if they are longstanding.
most frequent fracture configuration and commonly Dorsal frontal fractures of P1 occur relatively fre­
affect the forelimbs more than the hindlimbs. Typically quently. These fractures commonly affect the hindlimbs
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lameness is very apparent; however, soft tissue swelling although these can occur in forelimbs. There is no spe­
is often minimal, and varying degrees of fetlock joint cific gait characteristic associated with this injury, but
effusion may be present. Therefore, if a pastern fracture affected horses are often described as having a proxi­
is suspected, radiographic evaluation is recommended mal limb lameness. Frequently this injury is confused
prior to diagnostic anesthesia as it is possible to block a with tibial stress fractures. Diagnosis is often made
pastern fracture with palmar digital anesthesia. The with nuclear scintigraphy and confirmed by radio­
fracture often extends more distally in the weeks’ post‐ graphs. Unless extreme displacement occurs, which is
injury suggesting that these fractures are more extensive infrequent, the treatment is rest for 60–90 days.
than initially appreciated at the time of injury. Extracorporeal shockwave therapy (ESWT) can help
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Incomplete parasagittal fractures heal very well with promote healing, although these fractures heal consist­
internal fixation and have an excellent prognosis for ently without treatment. There is a good prognosis for
return to athletic use. However, complete biarticular return to racing.
parasagittal fractures typically have a much lower prog­ The proximal sesamoid bones and other components
nosis. Although the parasagittal configuration is by far of the suspensory apparatus are subject to tremendous
the most common fracture configuration seen, almost tensile forces and fatigue, especially when under full
any fracture configuration can occasionally be seen. load at high velocity. Several fracture types occur in the
proximal sesamoid bones, but apical fractures predomi­
nate. Other fracture types include midbody, basilar,
Fetlock
abaxial, and comminuted fractures, but all occur less
The fetlock is the single most common region affected frequently than fractures of the apex (Figure 9.2).
by lameness in the TB racehorse. The fetlock joints of Apical fractures are articular; therefore, joint effusion
both the forelimbs and hindlimbs are plagued with mul­ is usually observed if the fracture is displaced. There is
tiple problems that contribute to lameness, and they are pain on flexion and on focal pressure of the involved
the most commonly affected articular structure in the sesamoid. Diagnosis is confirmed radiographically, and
racehorse. One report indicates that up to 56% of the there is a good prognosis for return to racing with fore­
total days lost in training as 2‐year‐olds are attributed to limb involvement (67%) with an even better prognosis
fetlock pathology. Most are associated with some form for return to racing for hindlimbs (83%). The medial
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4
of cumulative stress‐related disease, which may involve sesamoid of the front fetlock carries the worst progno­
the bone, cartilage, or soft tissue. sis; only 47% return to race. A major determinant in
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Synovitis and capsulitis of 2‐year‐old training horses the prognosis is the integrity and degree of damage of
are common and often self‐limiting, as long as training the suspensory ligament; therefore, ultrasound evalua­
is reduced and the tissue is permitted to heal. The pre­ tion is critical.
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dominant clinical sign is joint effusion with or without Abaxial, transverse midbody, and basilar fractures
heat. Lameness is mild if present, but there is usually occur less commonly and carry a guarded prognosis for
resentment to flexion of the joint. Radiographs are unre­ future racing, with or without surgery. Surgical removal