Page 83 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

58 CHAPTER 1

VetBooks.ir 1.103 medial femoral condylar subchondral bone cysts
has been reported. Arthroscopic treatment carries a
reported 70% success rate in horses under 3 years
old. In general it appears that young horses with uni-
lateral medial femoral condyle cysts are most likely
to perform as intended. A much lower success rate is
reported in horses over 4 years old (35%). Too few
numbers of cysts treated in other locations are avail-
able to make definitive statements. Accompanying
DJD worsens the prognosis.
Currently, there is an overall fair prognosis for
young horses with unilateral medial femoral con-
dyle subchondral cysts treated arthroscopically, but
only a guarded prognosis in adult horses. Younger
horses, particularly those with cysts involving the
medial femoral condyle and where corticosteroids
Fig. 1.103 An arthroscopic view of the medial femoral
condyle of a 2-year-old Thoroughbred racehorse with are injected directly into the cystic lining, seem to
a subchondral bone cyst. Note the flattening of the have a favourable prognosis. In a recently published
condyle and an obvious defect in the cartilage. Probing paper, 75% of 20 cases of medial femoral condyle
with a needle allowed entrance into a large cyst, which cysts subjected to a screw technique were sound at
was treated by injection of corticosteroids into the cyst 120 days postoperatively. A guarded prognosis is also
cavity. (Photo courtesy Graham Munroe) given for all bone cysts for conservative treatment,
bilateral presentation and all other types of cyst.

Cancellous bone graft can be placed after debride- PHYSITIS (EPIPHYSITIS,
ment, but this does not appear to improve the PHYSEAL DYSPLASIA)
outcome. Stem cell placement may offer a future
treatment option. A useful simpler and cheaper Definition/overview
alternative method of treatment that is effective in Physitis is a form of DOD involving a disturbance of
young horses, before maturation of the subchon- endochondral ossification at the peripheral or axial
dral bone plate, involves the injection of corticoste- region of the metaphyseal growth plate, particularly
roids (usually triamcinolone) into the cystic lining, at the distal radius/tibia and distal third metacarpus/
either under arthroscopic or ultrasonographic guid- metatarsus of foals and young horses. It is mainly
ance. This technique can be spectacularly success- encountered in fast growing breeds such as the
ful in some cases, but in others, improvement may Thoroughbred.
be temporary and subsequent cystic enucleation is
required. Recently, a technique has been described Aetiology/pathophysiology
where a cortical screw is placed across the cyst. The cause of physitis is currently unclear, but it
While this is a more involved surgical technique, appears that compression trauma to the growth plate
early results appear promising. due to excessive exercise or overuse of one limb dur-
ing the most active growth phases of young horses
Prognosis can result in physitis. The condition is more com-
The prognosis depends on the joint affected, the mon where nutritional (lush pasture, high concen-
severity of the lesion, associated DJD, intended trates) and supplement excesses or deficiencies are
use of the horse and the treatment option selected. implicated, and some clinicians believe it may be
A 50% success rate with conservative treatment of another manifestation of OCD in the horse.