Page 82 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.2 The foal and developing animal 57

VetBooks.ir 30–60 minutes in the medial femorotibial joint) and 1.102
a partial improvement (50%) warrants radiographic
evaluation.

Differential diagnoses
Subchondral lucencies primarily associated with
advanced DJD, bone abscess.

Diagnosis
A full lameness examination should be carried out
and systematic diagnostic analgesia is required to
assess the relevance of any cystic structure within
a joint.
A full radiographic series for the affected joint
should be obtained. Certain views are more useful in
depicting cysts at different locations (e.g. caudocra- Fig. 1.102 Caudocranial radiograph of the stifle
nial view [Fig. 1.102] and flexed lateromedial view showing the femorotibial joint in a 4-year-old pony
of the femorotibial joints for subchondral bone cysts with lameness localised to this joint by intra-articular
of the medial femoral condyle). Note that the condi- analgesia. Note the large subchondral bone cyst in
tion can be bilateral, especially in the medial femo- the medial condyle of the distal femur and the large
rotibial joint, so the contralateral limb should always connection between the cyst and joint.
be radiographed for comparison. Different expo-
sure settings and slightly different proximodistal
obliquity of the radiographs are advisable to clarify helpful in cysts located elsewhere. Many of the
fully the presence of a cyst, especially in the medial conservatively treated cases are placed on NSAIDs
femoral condyle. Positive contrast arthrograms may to control the pain and inflammation in the joint(s).
also be useful in certain instances. Cysts vary in Various intra-articular medications have been
size from small indentations to a large radiolucent used, including corticosteroids +/– sodium hyaluro-
lucency depending on the stage of development of nate, with generally limited success and often only
the cyst. They are often oval or rounded in shape, temporary resolution in lameness in most cases.
usually confluent with the articular margin, and may Polysulphated glycosaminoglycans given either
have a sclerotic peripheral margin (see Chapter 1.4, intra-articularly or intramuscularly have also been
Fig. 1.303). Ultrasonography of the femorotibial used, often with a follow-up of long-term oral joint
joints may be useful in some cases to evaluate the supplementation with chondroitin sulphate and
cartilage contour of the femoral condyles. Bone scin- glucosamine.
tigraphy may reveal some subchondral bone cysts,
but this is not a consistent finding and may reflect Surgical
different stages of the cyst’s development. MRI and Surgical treatment has historically involved
CT can help locate and define more accurately cysts debridement of the cyst via arthroscopy (Fig. 1.103)
of the distal limb and may be a useful pre-surgical or arthrotomy or via a transosseous approach. The
intervention. method used depends on the location of the cyst and
surgeon preference. The cyst lining can be debrided
Management and all debris removed. However, recently there has
Conservative been a move away from aggressive debridement
Box or small-paddock rest for up to 6 months has because enlargement of the cyst and worsening
been successfully used in some medial femoral of lameness have been observed. Similarly, sub-
condyle bone cysts, but often it is only temporarily chondral bone forage is currently contraindicated.