Page 320 - Canine Lameness

292 18 Tarsal Region

injuries result in medio-lateral instability. Luxations or instability of the distal tarsal joints may
involve the plantar or dorsal intertarsal ligaments and the resulting instability may be dorso-
plantar and/or medio-lateral. The majority of these injuries are traumatic, but they may be due to
immune-mediated or (uncommonly) idiopathic disease. The proximal intertarsal joint (i.e. calca-
neoquartal and talocalcaneocentral joints) is the level most commonly involved but tarsometatar-
sal luxations are also encountered.
Treatment of these injuries may include nonsurgical approaches for mild injuries, but surgery is
generally recommended for complete (grade 3) sprains. Surgical treatment may include recon-
struction of the collateral ligaments, fracture fixation (e.g. for malleolar fractures), or partial and
pantarsal arthrodesis depending on the location and severity of the injury.
TARSAL REGION 18.4.1 Signalment and History

Dogs of all breeds and ages can be affected by traumatic tarsal luxations, although medium-to-
large, active dogs seem to be most often affected. Motor vehicle accidents are the most common
cause, but collateral injuries can also follow falls, running mishaps, and lower limb entrapment.
Collisions with vehicles can cause shearing injuries, which almost always happen on the medial
side of the tarsus. When the medial malleolus is ground away, medial collateral instability results.
Herding dogs can incur tarsometatarsal luxations when a foot is caught in the rungs of a gate dur-
ing a jump. When trauma is involved, the limb is initially carried. With time weight-bearing is
resumed, but severe (and apparently painful) lameness persists. With disruption of the dorsal liga-
ments, this lameness may be less severe compared to plantar ligament or collateral ligament
pathology. Please refer to Section 18.7.2 regarding idiopathic tarsal luxation and tarsal luxation
caused by immune-mediated disease.
Isolated rupture of one or both of the short lateral collateral ligaments has been reported in 6
young (3–40 month old) dogs, most of which were Retrievers (Sjöström and Håkanson 1994). This
injury was associated with fracture or fragmentation of the lateral trochlear ridge in three of these
dogs. It is not known if the talar injuries were strictly traumatic in origin or if osteochondrosis of
the lateral talar ridge was a predisposing factor.

18.4.2 Physical Exam

Diagnosis is straightforward when both the short and long collateral ligaments of one side are
completely ruptured. The affected limb is usually carried right after the ligament has been injured,
but as time passes most dogs begin using it again. When the limb is bearing weight, medial collat-
eral insufficiency allows valgus angulation and lateral collateral insufficiency allows varus angula-
tion of the foot. There may be a wound present over the medial (most common) or lateral aspect of
the tarsus; sometimes this wound is small compared to the extent of the injury beneath. The tarsus
will be swollen, with the swelling usually centered on the tarsocrural joint and more severe on the
injured side. Crepitus and luxation may be felt when the joint is manipulated. Testing the collateral
ligament integrity is done with the tarsus both in extension and in moderate flexion. This allows
for testing of the short and long collateral ligaments. The distal tibia is held steady, and varus and
valgus stress is applied to the pes. If the lower limb deviates laterally with the tarsus in extension
and flexion, complete disruption of the medial collateral ligaments is present. Similarly, if medial
deviation of the pes happens in both tarsal positions, the lateral collateral ligaments are completely
torn. If deviation only happens with the tarsus in extension, just the long part of the collateral liga-
ment is torn; instability only in flexion suggests injury to the short collateral ligaments. Isolated