Page 555 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Distal Limb 521

Horses with palmar/plantar subluxation/luxation are
also often very lame in the acute stage. The lameness
VetBooks.ir walk and the dorsal surface of the pastern will appear
may subside over time, but most will remain lame at the
concave (dished out) rather than straight or convex as
would occur with dorsal subluxation. In chronic cases
the heel bulbs may contact the ground, and excessive
hyperextension of the pastern and sinking of the fetlock
is noted when the horse is walked.
Dorsal subluxation can occur without any identifiable
structural abnormalities of the pastern or metacarpal/
metatarsal soft tissue structures. This occurs primarily in
the hindlimbs in young horses and lameness is usually
absent or mild. A dorsal swelling in the pastern region
may be evident when the affected limb is unweighted.
This type of subluxation is often dynamic in nature and
usually resolves during full weight‐bearing of the PIP
joint. An audible clicking sound often accompanies the
reduction of the joint. When the pelvic limbs are involved,
the condition is often associated with an upright confor-
mation (straighter than normal hocks and stifle angles). 63
With persistent dorsal subluxation of the PIP joint, an
obvious swelling over the dorsal aspect of the pastern
region is often evident, and the fetlock may appear
slightly more extended (dropped) as compared to the
contralateral unaffected limb. The dorsal swelling may
appear similar to that associated with high ringbone,
but on closer observation an abnormal alignment
between P1 and P2 is found. However, with chronicity,
both clinical and radiographic abnormalities consistent
with OA of the PIP joint may develop. Lameness is vari-
able and inconsistent in these cases and often depends
on the secondary changes that develop within the joint.
Figure 4.99. Dorsoplantar stress radiograph demonstrating
complete rupture of a collateral ligament of the PIP joint. Arthrodesis
Diagnosis of the joint is the recommended treatment.
A tentative diagnosis can usually be made from
the history and physical examination of the horse. making surgical realignment difficult. Dorsal subluxa-
Radiographs should be taken to confirm the diagnosis tions may also be treated with arthrodesis if they fail to
and identify concurrent abnormalities such as fractures respond to other methods of treatment. In most cases
or OA. Stress films may be needed to confirm medial/ the subluxation is best treated surgically before exces-
lateral subluxation because the phalanges can often sive scar tissue has developed to permit more accurate
remain in correct anatomic alignment unless pulled and easier alignment of the joint. Horses with dorsal
medially or laterally (Figure 4.99). Dorsal and palmar/ luxation of the PIP joint with secondary OA are also
plantar subluxations/luxations are usually obvious on best treated with arthrodesis. See the section on OA of
standing lateral to medial views of the pastern. the PIP joint for more information on arthrodesis.
Horses with intermittent dorsal subluxation with no
apparent lameness may be treated conservatively. Horses
Treatment with bilateral upright hindlimb conformation and dorsal
The treatment of choice for medial/lateral and palmar/ subluxation often respond to anti‐inflammatory medica-
plantar subluxations/luxations of the PIP joint is arthro- tion and a controlled exercise program. Horses with inter-
desis of the joint. External coaptation with a cast or mittent dorsal subluxation of the pelvic limb associated
Kimzey splint (Kimzey Leg Saver Splint; Kimzey, Inc., with excessive tension of DDFT have been treated success-
Woodland, CA) may be successful in adult horses man- fully with transection of the medial head of the DDFT.
63
aged acutely, but instability of the PIP joint may pre- The approach was between the DDFT and the suspensory
clude successful realignment. Unlike medial/lateral ligament at the level of the proximal third of the third
luxations of the fetlock joint, similar luxations of the metatarsal bone, and a 2.5‐cm segment of the tendon was
PIP joint do not respond well to casting alone and often removed. Alternatively, surgical transection of the acces-
develop secondary OA and persistent lameness. sory ligament of the DDFT may be of benefit.
Conservative treatment of palmar/plantar subluxations/
luxations is usually unsuccessful, and surgical arthrode- Prognosis
sis is often the only option to realign the phalanges.
Chronic palmar/plantar subluxations/luxations can lead Although there are few reports on long‐term follow‐
to fibrosis of the PIP joint in an abnormal position, up, the prognosis is good for survival and fair to good