Page 316 - Canine Lameness

288 18 Tarsal Region

A number of tendons insert on or (in the case of digital flexors and extensors) pass over the tarsal
region. The major flexors of the tarsus include the cranial tibial tendon, which passes obliquely from
lateral to medial over the central tarsal bone to insert on the first and second metatarsal bones, and
the fibularis (peroneus) longus and brevis tendons, which insert on the fourth tarsal bone and plantar
surfaces of the metatarsals (longus) or the fifth metatarsal bone alone (brevis). The major extensor of
the tarsus is the common calcanean (Achilles) tendon, which is composed of three major compo-
nents: the gastrocnemius tendon (GT), which inserts on the tuber calcanei; the conjoined tendon,
formed from portions of the biceps femoris, semitendinosus, and gracilis tendons, which also inserts
on the tuber calcanei; and the superficial digital flexor tendon (SDFT), which passes over the tuber
calcanei on its way to the pes. The CCT will be discussed in greater depth later in Section 18.5.
TARSAL REGION extensor of the first digit; the fibularis (peroneus) longus and brevis; the long and lateral digital
Seven tendons have synovial sheaths as they pass the tarsus: the cranial tibial tendon and long

extensors; and the deep digital extensor tendon. The sheath of the deep digital extensor communi-
cates with the tarsocrural joint. The cranial tibial tendon, the fibularis longus and fibularis brevis
tendons, and the SDFT have bursae near their insertions in the tarsal region (Johnson 1985).

18.3 Fractures of the Tarsal Region

Pain in the tarsal region may originate from fractures of the metatarsi (discussed in Chapter 12),
fractures of the tarsal bones and fractures of the distal tibia and fibula (lateral malleolus). In imma-
ture animals, Type I and II Salter-Harris fractures (Chapter 13) are most commonly observed. In
mature animals, malleolar fractures or fractures of the distal tibial metaphysis are the most com-
mon types. Fractures of the malleoli may result in tarsocrural luxations because the collateral liga-
ments originate there.
Because the tarsal bones are held together so tightly by ligaments, these fractures often involve
more than one bone and may be accompanied by intertarsal luxations. Displaced fractures or luxa-
tions of the central tarsal bone, which acts a medial strut, cause angular deformity of the tarsus.
A wide variety of fractures of the specific tarsal bones have been described and treatment varies
based on the fracture specifics (Carmichael and Marshall 2018). Simple fractures and single-bone
luxations are generally treated with internal fixation, while partial tarsal arthrodesis (i.e. fusion of
joints distal to the tarsocrural joint) is used to treat injuries (including many calcaneal fractures) distal
to the tarsocrural joint. Pantarsal arthrodesis (i.e. fusion of all tarsal joints including the tarsocrural
joint) may be needed to treat articular fractures of the talus or tibia and other severe injuries.

18.3.1 Signalment and History

As for any fracture, trauma is the main cause which can happen to dogs of any age/signalment.
Nevertheless, tarsal fractures and luxations are predominantly seen in medium-to-large, active
adult dogs. Bone fractures of the tarsal region are most commonly the result of a single traumatic
event. However, in racing Greyhounds, repetitive stress can cause fatigue fractures of the central
tarsal bone, and Dalmatians have been reported to suffer from atraumatic fractures of this bone
(Armstrong et al. 2019). Racing Greyhounds develop central tarsal bone fractures (and related
injuries, especially to the calcaneus and fourth tarsal bone) in the pelvic limb opposite to the direc-
tion of turn on an oval racetrack. Sighthounds and Dalmatians seem to be particularly susceptible
to central tarsal bone injuries (Armstrong et al. 2019). In most cases, there is a history of acute
onset of non-weight-bearing lameness. Avulsions of the tuber calcanei are occasionally seen in
immature dogs following falls or jumps.