Page 181 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

156 CHAPTER 1

VetBooks.ir 1.289 of training. Fragmentation typically affects the dorsal
articular margin(s) of the distal aspect of the radial
carpal bone but can also involve the articular margins
of the distal intermediate carpal bone, distal lateral (or
medial) radius, proximal radial carpal bone, proximal
intermediate carpal bone and proximal third carpal
bone. Subchondral bone of the parent bone may show
pre-existing pathology. Palmar carpal bone frag-
ments are usually traumatic and have been reported
in horses recovering from general anaesthesia.

Clinical presentation
Horses usually present with acute swelling/lameness
involving the carpal joint(s). Palpation may reveal
irregularity/crepitus along the dorsal margin of the
affected bone. Lameness is exacerbated by carpal flex-
ion and horses may resent passive flexion of the carpus.

Differential diagnosis
Carpal bone slab or other types of fracture; carpal
OA; MPICL injury.

Diagnosis
Fig. 1.289 Dorsolateral/palmaromedial oblique
radiograph of a horse with chronic osteoarthritis of Diagnosis is confirmed by response to intra- articular
the mid-carpal joint. Note the extensive osteophyte anaesthesia and subsequent radiographic evaluation.
remodelling on the distal radiocarpal and proximal Osteochondral fragmentation may be present bilat-
third carpal bones. (Photo courtesy Graham Munroe) erally, so radiography of the contralateral carpus is
recommended. Conventional views of the carpus
may be supplemented by a variety of oblique and
through drilling in a fanning fashion has led to good special skyline projections (Figs. 1.290, 1.291).
improvement. Partial or pancarpal arthrodesis of the
carpus is described for advanced cases. Management
Arthroscopic removal of osteochondral fragments is
Prognosis recommended, particularly in racing or sports horses.
The prognosis for horses with established carpal OA Evaluation of cartilage and subchondral bone quality
is poor. Horses generally remain lame and advanced and presence of other lesions can be documented at sur-
cases can lead to conformational abnormalities. gery and may affect prognosis (Fig. 1.292). Removal of
traumatic palmar fragments can be a challenge, par-
OSTEOCHONDRAL FRAGMENTATION ticularly those involving the palmar radial condyle.
In some cases, multiple shards are present, and removal
Definition/overview of all fragments may be difficult to achieve.
Osteochondral fragmentation of the carpus is also
known as ‘chip fractures’. Prognosis
Prognosis following osteochondral fragment
Aetiology/pathophysiology removal has been linked to cartilage quality at sur-
Osteochondral fragmentation may be a part of the gery. Increasing cartilage loss is associated with
pathophysiology of OA or be a distinct entity in itself, reduced return to racing, particularly in the middle
particularly in racing breeds or sports horses as a result carpal joint.