Page 228 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.5 The hindlimb 203

VetBooks.ir 1.389 of OA. The release of inflammatory mediators by
the cyst soft-tissue lining is thought to promote local
inflammation and synovitis. To reduce inflammatory
mediator production by the cyst lining, corticoste-
roids have been injected directly into the cyst lining
under ultrasonographic guidance, or arthroscopic
guidance under general anaesthesia, with the lat-
ter providing more reliable accuracy. The cysts can
also be debrided arthroscopically, again under gen-
eral anaesthesia, either as a primary treatment or in
those animals in which corticosteroid medication has
proved unsuccessful. Resurfacing the medial femoral
condyle with techniques such as mosaic arthroplasty
and chondrocytes or stem cells in fibrin glue have been
published, but they are not currently widely available.
More recently, a cortical bone screw has been placed
across the cyst under radiographic and arthroscopic
guidance. Drilling through the cyst and the ongoing
Fig. 1.389 Caudocranial radiograph of the left stifle presence of the screw appear to cause the cyst to fill
of a 6-year-old Welsh gelding. A depression in the with hard bone, leading to an improvement in clinical
subchondral bone of the medial femoral condyle is signs, and the results in a relatively small number of
seen to communicate with a flask-shaped radiolucency published cases are promising.
within the condyle itself. This is an osseous cyst-like
lesion of the medial femoral condyle. Prognosis
Prognosis depends on the size of the defect in the joint
surface associated with the cloaca of the cyst. Although
which is most easily seen on a caudocranial projec- ultrasonographic measurement may provide a guide
tion (Fig. 1.389). If a cyst is identified in one stifle, to the size of the opening, only arthroscopic assess-
then the contralateral stifle should also be imaged ment of lesion size has proved to be a reliable guide to
as lesions can be bilateral. Ultrasonography of the prognosis, with lesions of 15 mm diameter or smaller
articular surface of the medial femoral condyle can more likely to have a positive outcome. The prognosis
be achieved if the limb is held in a flexed position, is guarded to fair for return to athletic soundness for
although this technique requires some practice to lesions that undergo direct treatment of the cyst, with
master. Ultrasonographic examination should con- current studies showing a similar outcome whether
firm a defect in the subchondral bone and articu- the cyst is debrided, injected under arthroscopic guid-
lar cartilage and can be useful in helping to define ance or treated with a cortical screw. Where OA is
the size of the opening to the cyst, which can affect evident at the time of treatment the prognosis is sig-
prognosis. Arthroscopy of the joint allows identifica- nificantly poorer.
tion of the cyst opening and can facilitate treatment.
SOFT-TISSUE INJURIES OF
Management THE STIFLE JOINT
As with other causes of synovitis, conservative treat-
ment with rest, systemic NSAIDs and possibly intra- Definition/overview
articular medication may be adequate to return the The stifle is a complex structure with an array of
animal to soundness in the short term. Direct treat- ligaments maintaining normal movement, two large
ment of the cyst is likely to be required to provide long- fibrocartilaginous menisci and large areas of joint
term resolution of the lameness associated with the cartilage, all of which are prone to injury. Soft-tissue
lesion and reduce the likelihood of the development injuries of the stifle include meniscal tears or lesions