Page 165 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

140 CHAPTER 1

VetBooks.ir Aetiology/pathophysiology Differential diagnosis
Fetlock OA; OCD; osteochondral fragmentation;
POD is thought to relate to repetitive high strains
on bone and articular tissues in the distal condyles
of the third metacarpus/metatarsus experienced in PSB fracture.
training and racing. Affected cases will show carti- Diagnosis
lage wear lines and loss and collapse of the articular Radiography may reveal minimal signs to changes
surface with commensurate underlying subchon- in bone density in the subchondral bone in the distal
dral bone pathology at post-mortem. Higher POD and palmar/plantar aspect of the condyles. Changes
grades have been associated with use of intra- in bone density include focal radiolucencies in the
articular corticosteroids (particularly triamcinolone) palmar/plantar condyles, alteration to the outline
while in training, whereas lower grades are reported of the subchondral bone and sclerosis of the pal-
in horses with longer intervals between races. mar condyles. Radiographic projections, including
flexed dorsopalmar/plantar and elevated oblique
Clinical presentation views, have been used to improve diagnosis of this
POD is suspected in young racehorses with lameness condition. In some cases, changes in joint incongru-
in one or more limbs involving the fetlock region. In ity may be present with evidence of flattening of the
some cases there are no signs referable to the fetlock. condyle (Fig. 1.253). This latter finding may repre-
Lameness may range from mild and performance sent collapse of the articular surface. Radiographic
limiting to overt pain localised to the fetlock joint. evidence of OA may also be present, but this is
A better response to perineural rather that intra- uncommon. On nuclear scintigraphy, horses affected
articular analgesia often occurs and is likely to be due with POD will show moderate to marked increased
to the underlying pathophysiology of the condition. radiopharmaceutical uptake in the condylar region
of the fetlock. MRI can be used to differentiate
POD from other fetlock pathology (e.g. prodromal
1.253 condylar fracture); in one study over 50% of racing
Thoroughbreds with lameness localised to the fet-
lock region had signs consistent with POD (often
biaxially) (Figs. 1.254, 1.255).

Management
Although intra-articular medication is associated
with development of POD, it is still commonly
used in its management. Alterations to training
regimes can be associated with positive outcomes.
Short periods of rest, however, may be associated
with increased severity of POD. This is thought to
be related to lesions still in the resorptive phase of
healing, which may lead to severe focal changes on
return to racing. POD is a common finding at post-
mortem and likely to be a significant contributor to
wastage among Thoroughbred racehorses.
Fig. 1.253 Lateromedial radiograph of the left hind
fetlock joint in a 5-year-old Thoroughbred flat racehorse Prognosis
with bilateral hindlimb lameness. Note the flattening of Prognosis with this condition can be variable. Mild
the plantar condyle of the distal third metatarsal bone cases often resolve but some cases will be recur-
(arrow), with wedge-shaped subchondral bone sclerosis. rent. Severity has been linked to reduced race
(Photo courtesy Graham Munroe) starts/earnings.