Page 695 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 661

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A B

Figure 5.64. Nuclear scintigraphy can provide information about talocalcaneal OA, and the image on the right (B) corresponds to an
specific conditions that occur in the tarsal region that are associated area of calcification of the plantar ligament.
with the bone modeling. Image on the left (A) is of horse with

Figure 5.65. Cross‐sectional imaging techniques such as CT central tarsal bone and can be used to more accurately place
eliminates the superimposition of the different bones that make up screws to compress the fractures.
the tarsus. This CT demonstrates a comminuted fracture of the
scintigraphy) (Figure 5.65). Subchondral cyst‐like severity of radiographic changes compared with lameness
lesions, osteolytic lesions of any of the tarsal bones, in many horses (Figure 5.66). Protocols for MRI of the
degenerative changes of the DT joints, sclerosis of any of tarsus have been suggested, and equine tarsal MRI anat-
the tarsal bones (but particularly T3), and reaction omy has been described using both low‐ and high‐field
around the interosseous ligaments can all be identified systems. 13,14,21,45,83,125 In the normal tarsus, articular carti-
very clearly with CT. CT is especially helpful to deter- lage of the DT joints is very thin, which does not allow for
mine the extent and complexity of a fracture better than distinction of proximal and distal cartilage layers in these
radiography. Focal lesions located between the tarsal joint spaces. Subchondral bone plates of the DT bones
bone surfaces that are difficult or even impossible to and the MTIII have homogeneous low signal intensity
detect with radiography and ultrasonography can be with a regular osteochondral junction and a smooth but
better characterized with CT. undulating deep border. In competition horses that
undergo high intensity training, subchondral bone thick-
MRI of the Tarsus ness is greater medially in the DIT joint and laterally in
the TMT joint. 21,125 This repeatable thickness pattern of
MRI can be useful for evaluation of DT pain because subchondral bone is lost in horses with DT lameness. For
there is a lack of correlation between the presence and instance, cadaveric tarsi from horses with histories of DT