Page 700 - Adams and Stashak's Lameness in Horses, 7th Edition

666 Chapter 5

Nuclear Scintigraphy pain originating from the proximal plantar region
suggestive of PSD.
There is a repeatable pattern of RU in the DT region
VetBooks.ir of normal horses, and an alteration in this pattern could be under general anesthesia. Acquiring diagnostic images
MRI examination of the tarsus requires that the horse
provide an indication of tarsal pathology, related to
of the tarsus in the horse in a low field strength magnet
altered patterns of bone remodeling. Nuclear scintigra-
phy is often unnecessary, but it can be helpful in difficult (usually found in standing systems) may prove to be dif-
ficult because of slower acquisition times and the inher-
horses and those horses with performance problems ent motion that occurs proximally on the limb. The
rather than overt lameness. IRU may be focal or more contralateral limb would ideally be examined for com-
diffuse, and this can vary between horses. Focal increased parison. See the imaging chapter on magnetic resonance
uptake may reflect intertarsal ligament enthesopathy imaging (MRI) for further details.
rather than OA. Intense IRU may be present in the Using MRI, horses with DT pain have been found to
absence of radiological abnormalities, and these horses have intertarsal ligament damage, focal cartilage dam-
tend to respond poorly to intra‐articular medication, age, and localized bone pathology including cystic
despite a positive response to intra‐articular analgesia. lesions and microfractures. It is therefore possible that
Horses with diffuse radiopharmaceutical uptake tended DT pain incorporates a variety of different conditions,
to respond to treatment better than those with focal culminating in end‐stage OA.
uptake. Diffuse uptake possibly indicates more gener-
103
alized inflammation from use as compared to focal
articular degeneration demonstrated by focal peaks of Differentiating DT Joint Pain from Proximal
uptake. The distribution of inflammation may bear Plantar Region Pain
prognostic value as well. While nuclear scintigraphy can
be useful adjunct to confirm DT joint modeling activity, PSD of the hindlimb has become a frequently diag-
it may also help to document other sites of involvement nosed cause of acute and chronic hindlimb lameness in
(Figure 5.68). mature horses that perform dressage, eventing, and gen-
eral‐purpose work. 38,39,82 The recent increase in the diag-
nosis of PSD may be due to improvement by veterinarians
MRI and equine professionals in recognizing this condition.
The primary indication for MRI is indicated when However, lameness referable to this region is often ini-
pain has been localized to the tarsal region using tially assumed to originate from the DT joints.
perineural analgesia or by intrasynovial analgesia, but Subsequent intra‐articular injection of corticosteroids
there are no radiological or ultrasonographic into the DT joints may provide a local anti‐inflamma-
abnormalities sufficient to explain the degree of lame- tory effect, which can minimize the pain associated with
ness. However, an effusive TC joint may be a stronger the active desmitis. This may allow the resumption of
indication for exploratory arthroscopy than for an work before appropriate repair has occurred, leading to
MRI as the ability to surgically address the problem (if further damage to the SL. An accurate early diagnosis of
found) can be accomplished during the same anesthetic PSD is critical to minimize further damage to the SL and
procedure. However, the most common use of MRI of justify aggressive and expensive treatment to salvage the
the DT joints is to further evaluate horses that have horse’s career. In one study of 40 horses with lameness

A B
Figure 5.68. Lateral scintigram (A) and radiograph (B) of the tarsus of a horse with distal tarsal OA. There is diffuse uptake within the
distal tarsal joints and joint space narrowing and lysis within the DIT joint (arrows) visible on the radiograph.