Page 168 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.4 The forelimb 143

VetBooks.ir 1.258 1.259

Figs. 1.258, 1.259 Examples of lateromedial radiographs of fetlock joints with mild (1.258) and severe (1.259)
changes of osteoarthritis. In the mild case, there is an example of subtle periarticular osteophyte formation on
dorsoproximal P1 and remodelling of the proximal dorsal part of the sagittal ridge. In the severe case, these are
accompanied by dorsoproximal proximal sesamoid bone osteophytes, subchondral bone sclerosis and reduction
in the joint space.

may provide temporary improvement of signs. In Clinical presentation
severe cases where salvage of the horse is necessary, The acutely, severely lame horse may have obvious
fetlock arthrodesis can be performed. anatomical anomalies present, although in closed
subluxations the articular surfaces may be congru-
Prognosis ent. There is usually marked soft-tissue swelling
Long-term prognosis for horses with fetlock OA and palpation/manipulation of the joint will usu-
is poor. ally reveal instability. Open subluxations show overt
derangements and often severe contamination.
FETLOCK JOINT SUBLUXATION
Differential diagnosis
Definition/overview Severe joint sprain/trauma; intra-articular fracture;
Subluxation of the metacarpo/tarsophalangeal joint synovial sepsis; suspensory breakdown; pastern
may be open or closed. subluxation.

Aetiology/pathophysiology Diagnosis
Fetlock joint subluxation usually occurs due to Clinical examination may indicate severe disruption
trauma (e.g. foot trapped in a cattle grid or due to to the joint. Radiography will reveal the presence
a fall). Severe traumatic disruption of the medial or of the luxation, although stress radiographs may be
lateral collateral ligaments and tearing of the joint required for a definitive diagnosis. Radiographs are
capsule and other supporting structures leads to also advisable to check for concurrent injuries such
incongruity of the articular margins. Avulsion frac- as avulsion fractures (Fig. 1.260). Ultrasonography
tures may also occur. is also indicated to assess damage to the collateral