Injuries to the tarsus generally involve fracture of one or more bones, impairment of ligaments, or occasionally a combination of both these injuries. Ligamentous injuries are most often seen in athletic animals, whereas fractures are common in a variety of animals. Ligamentous injuries of the tarsus resulting in varying degrees of instability are relatively common in athletic breeds because of the propulsive force supplied by the hindlegs. Unlike those of the carpus, tarsal injuries are more likely to be caused by spontaneous overstress rather than by outside traumatic forces. Conservative treatment of second-degree and third-degree ligamentous injuries by cast immobilization is not recommended because permanent instability is the usual result (see Chapter 7). Aggressive surgical treatment is much more rewarding, but it does require a good working knowledge of the anatomy of the region. Unfortunately, the official terminology of the tarsus differs greatly from that in current popular use.
OVERVIEW
Anatomy of the HindpawThe bony anatomy of the hindfoot is complicated and must be well understood before any repairs are attempted. Figure 20-1 reviews these bones and provides a comprehensive resource for interpreting radiographs. Ligaments of the hock and tarsus are shown in Figure 20-2. Beginning at the tarsocrural joint and continuing distally, the terms cranial and caudal are replaced by the terms dorsal and plantar.The bones of the tarsus are arranged in several levels, with a complex arrangement of ligaments. The joint between the tibia and fibula and the talus and calcaneus is the tarsocrural joint, often called the tibiotarsal, talocrural, or hock joint. It consists of both the talocrural and talocalcaneal joints, which are continuous with 661 20 Fractures and Other Orthopedic Injuries of the Tarsus, Metatarsus, and Phalanges each other. Intertarsal joints include all articulations between tarsal bones, with four of them named specifically, as follows:1. Talocalcaneal joint. The joint between the talus and calcaneus. 2. Talocalcaneocentral joint. This joint is primarily an articulation between the talus and central tarsal bone, but the joint capsule is continuous with the calcaneus. 3. Calcaneoquartal joint. The joint between the calcaneus and the fourth tarsal. This joint and the talocalcaneocentral joint collectively are known as the "proximal intertarsal joint." This name is useful to the surgeon because of the awkwardness of the official names. 4. Centrodistal joint. The joint between the central tarsal bone and the distal numbered tarsal bones. The common name is the "distal intertarsal joint."The remaining joints of the hindpaw include the following:1. Tarsometatarsal joints. The joints between the distal tarsal and metatarsal bones. 2. Metatarsophalangeal joints. The joints between the metatarsal bones and the first phalanges. 3. Interphalangeal joints. The joints between the first and second and second and third phalanges.The most common ligamentous injuries of this region involve the collateral ligame...