Page 709 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 675

develops synovitis, effusion, and moderate lameness calcaneal OA as the cause of lameness (Figure 5.75). The
later in their career. These horses should have these frag- lateromedial radiographic view is the best projection to
VetBooks.ir find cartilage damage consistent with OA at time of sur- including subchondral bone lysis, sclerosis, and irregular
evaluate this joint for changes consistent with OA
ments removed arthroscopically. It is not uncommon to
joint space width. Nuclear scintigraphy can demonstrate
gery. These horses can be difficult to keep sound because
of persistent low‐grade lameness. marked IRU in the plantaromedial aspect of the tarsus.
In the largest reported case series of 18 horses with
OA of the Talocalcaneal Joint talocalcaneal OA, 14 horses were treated conserva-
tively with stall or pasture rest, with or without intra‐
The talocalcaneal joint is a curved articulation articular corticosteroids, HA, or PSGAG, and all
between the plantar aspect of the talus and the dorsal remained lame. Intra‐articular corticosteroids appeared
aspect of the calcaneus. Its soft tissue support arises to have little effect on any horse. Follow‐up exams
133
from 4 ligaments—the medial, lateral, proximal, and often demonstrated a rapid progression of radiographic
60
interosseous talocalcaneal ligaments. The mechanics of changes. Because of the poor response to conservative
this joint have not been described, but it is considered a management, more aggressive therapies are now
low‐motion joint. being attempted. Subchondral forage and local neurec-
OA of the talocalcaneal joint is not common, and tomy have been utilized but have been unsuccessful. Six
descriptions of this condition are based on case horses have had a surgical arthrodesis using 2 or 3 5.5‐
reports. 134,139 However, when it occurs, it is usually a mm screws placed in a neutral fashion. All of these
moderate to severe unilateral hindlimb lameness. There horses improved significantly, but none became
are usually no localizing clinical signs. Lameness is typi- sound. Interestingly, one of these horses developed
cally exacerbated by proximal limb flexion of the contralateral talocalcaneal OA 2 years later. While sur-
hindlimb. The clinical signs resemble those of horses gical arthrodesis is now the treatment of choice, the
with DT OA but tend to be more severe. The cause of prognosis remains poor for a return to performance
this condition is unclear, but because of the usually sud- soundness.
den onset of lameness, it is assumed to be an acute soft
tissue injury probably related to disruption of the taloc-
alcaneal ligaments. Developmental Orthopedic Disease of the Tarsus
Diagnosis requires elimination of the lameness by Developmental orthopedic disease (DOD) is a term
diagnostic analgesia and confirmation with diagnostic used to describe many orthopedic problems seen in the
imaging. Talocalcaneal joint analgesia has not been young horse. It is discussed in further detail in
found to effectively eliminate the lameness and at best Chapter 10. The term describes a series of growth dis-
gives only partial improvement. Perineural tibial and turbances of young horses including OC (OCD), SCLs,
peroneal analgesia has been the most reliable method of angular deformities, flexural deformities, physitis,
reducing the lameness. Clinical examination, history, cuboidal bone abnormalities, and juvenile OA. All the
results of regional analgesia of the tibial and peroneal forms of DOD can occur in the tarsus.
nerves, the presence of radiographic changes of this OC of the TC joint occurs at very consistent sites. 64,66
joint, and nuclear scintigraphy can help to confirm talo- TC OC tends to occur at the edges/limits of the talus

A B

Figure 5.75. Horses with talocalcaneal osteoarthritis (OA) (A) and MRI (B; arrows) can be very helpful to identify the site of
usually present with unilateral moderate to severe hindlimb bone remodeling/pathology within the joint.
lameness without localizing clinical signs. Nuclear scintigraphy