Page 137 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

112 CHAPTER 1

VetBooks.ir 1.195 1.196

Figs. 1.195, 1.196 (1.195) Dorsal T1-weighted MR image of the distal interphalangeal (DIP) joint.
There is narrowing of the medial half of the joint space with loss of the normal 3-layer appearance of the
articular cartilage and synovial fluid (see lateral half of the joint space). Instead there are focal hypointense
areas of cartilage signal loss, where cartilage is replaced by pooling of synovial fluid (arrow). (1.196) Dorsal
fat-suppressed MR image of the same DIP joint. There is hyperintense osseous fluid signal indicative of
subchondral bone oedema in the medial half of the distal phalanx adjacent to the DIP joint (arrows).

usually triamcinolone, will be required to resolve the Prognosis
lameness. The use of intra-articular corticosteroids Horses with primary synovitis/capsulitis, without
is not without controversy. Methylprednisolone has radiographic abnormalities, have a good prognosis
been shown to be detrimental to cartilage, and even for return to their previous level of performance
though triamcinolone has shown some chondro- with intra-articular medication, rest and progressive
protective effects in relatively short-term studies, rehabilitation. The prognosis for horses with radio-
clinical experience suggests that repeated injection graphic signs of true OA of the DIP joint is guarded
in the face of continued exercise may lead to acceler- to poor. Many joints can be managed medically for
ated cartilage degeneration. Low dosages have been months to years, but eventually performance will
advocated (6 mg or less), but higher dosages above deteriorate and lameness will become refractory to
10 mg are often required to resolve clinical lame- all treatments.
ness. Anecdotally, it has been suggested that the total
body dose of triamcinolone should not exceed 18 mg COLLATERAL DESMITIS OF THE
because of a possible link with iatrogenic laminitis, DISTAL INTERPHALANGEAL JOINT
especially in large, overweight Sport horses. More
recently, OA of the DIP joint has been treated with Definition/overview
new intra-articular preparations such as stanazo- MRI findings have suggested that collateral desmitis
lol and polyacrylamide gels. Publication of small of the DIP joint is the second most important soft-
case series suggests a potential beneficial effect for tissue injury responsible for foot lameness. The func-
these preparations in horses that have become non- tion of the collateral ligaments is to support the DIP
responsive to intra-articular medication with hyal- joint in its movement in the sagittal, frontal and trans-
uronan and triamcinolone. verse planes. It has been determined that asymmetric