Page 721 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 687

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A B
Figure 5.89. Chronic infection of the ST may lead to substantial bone production arrows) and soft tissue swelling (arrowheads).
proliferative bone response and an established infection of the (B) Ultrasound image of tarsal sheath demonstrating moderate
tarsal sheath. (A) Oblique radiograph demonstrating extensive new bone lysis of the ST associated with osteomyelitis.

especially in open injuries. Involvement of the gliding sur- Conclusions of that study were that fragmentation of
face of the ST is a key parameter in the decision for sur- PTT appeared to occur more frequently in warmbloods
gery. If the fracture involves a significant amount of the but more importantly that it was not usually associated
flexor surface, reconstruction and reattachment with cor- with lameness. Affected horses remained clinically and
tical screws may be considered, especially if the tendon radiographically stable over time. The information from
sheath was not penetrated at the time of injury. If treat- this report is important for practitioners who perform
ment is delayed, proliferative changes can develop, lead- radiographic screenings during prepurchase examina-
ing to chronic lameness with a poor prognosis for future tions. Finding fragmentation of PTT does not appear to
usefulness of the horse. With immediate, effective treat- be a risk factor for the development of lameness associ-
ment, a guarded prognosis for return to athletic is typi- ated with the tarsus (Figure 5.90).
cal. Neglected cases have a grave prognosis.
SOFT TISSUE INJURIES OF THE TARSUS
Fragmentation of the Proximal Tubercle of
the Talus (PTT) Tarsal Collateral Ligament Injury
The proximal tubercle of the talus (PTT) is situated in The distal tibia is quadrangular in form and larger
the plantar aspect of the tarsus on the proximal and medially than laterally. These grooves and the corre-
medial region of the talus. The anatomy of this region of sponding trochlear ridges of the talus are directed
the tarsus is complex with a variety of ligaments and obliquely forward and laterally and are bound on either
synovial attachments associated with the PTT. side by the tibial malleoli. The tibial malleoli have exten-
Fragmentation of the PTT in horses is rare, and its clini- sive CL attachments from both the long and short
cal significance is questionable. The etiology of frag- components, and their anatomy has been previously
mentation of PTT is unknown, but OC has been described in detail. The lLCL has distal attachments
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suggested to have a role. The dorsal 45° medial to plan- to the talus, calcaneus, T4, T3, and MT4 bones. There
tarolateral oblique view or lateromedial view is are two sLCLs that lie axial to the lLCL. The long medial
reported to demonstrate the fragment best. A flexed collateral ligament (lMCL) has distal attachments to the
lateromedial, flexed dorsoplantar, and plantaroproxi- fused first and second tarsal bones, talus, CT and T3
malplantarodistal oblique (calcaneal skyline) views may bones, and MT2 and MT3 bones. There are three short
also help identify the fragment. medial collateral ligaments (sMCL) that, like their lat-
In one report 9 horses with fragmentation of PTT eral counterparts, lie axial to the MCL and are named
were identified, seven of which were Warmbloods. according to their respective insertions.
50
Diagnosis was made based on radiographic findings, but The stability of a TC joint is a product of the congru-
ultrasonography and CT were also utilized in some of ency of the joint surfaces, the integrity of the joint
the horses. Less than half (3/9) had TC joint effusion, capsule, and the strength of the CLs. In general, CLs
and only one horse was lame and that horse had a his- typically have a uniform fascicular orientation and,
tory of prior trauma and resultant lateral tibial malleo- therefore, a homogeneous sonographic appearance. The
lus fracture. Flexion tests did not produce lameness. One lLCL spirals during flexion and straightens during
horse underwent arthroscopy, but the fragments were extension as it takes the load from the sLCLs. A mixed
not visible and it was presumed that the fragments were arrangement of fascicles is necessary to allow the CLs to
extra‐articular. function in both extension and flexion. 34,35 In the TC