Page 134 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.3 The foot 109

VetBooks.ir prognostic indicator and may affect the decision to apparatus via intra-articular medication of the DIP
joint and the relatively low incidence of diseases of
attempt internal fixation.
Management the DIP joint on MR images of horses with foot pain.
Rest and immobilising the hoof in a manner simi- Aetiology/pathophysiology
lar to that used for distal phalangeal fractures have Synovitis, capsulitis and OA of the DIP joint are
been used, but fibrous unions and subsequent OA are usually sequelae to trauma, infection or, occasion-
common. Better results have been reported follow- ally, subsequent to OCD/subchondral bone cysts.
ing elevation of the heels by 12° for 2 months, with Trauma may be repetitive and low grade associated
gradual reduction by 3° at a time over a 4-month with constant high athletic performance, which
period. Internal lag screw fixation of acute distal may be exacerbated by poor foot conformation.
sesamoid bone fractures has been reported in two Alternatively, trauma may result in more acute inju-
uncontrolled studies, with seemingly good results. ries such as intra-articular fractures, collateral des-
Fractures that are less than 4 weeks old have a sig- mitis and direct damage to the articular cartilage.
nificantly better prognosis for soundness. Fractures By definition, OA is progressive; however, not all
treated by internal fixation may heal by osseous or horses with DIP joint pain suffer from OA, and tran-
fibrous union, but internal fixation appears to pro- sient synovitis is not uncommon following either a
tect against the onset of OA of the DIP joint. The single episode of trauma or repetitive trauma of
technique requires special equipment and expertise. short duration.
This surgery is seldom performed because of the
technical challenges and the lack of controlled data Clinical presentation
supporting superior results. Complications include Lameness associated with DIP joint pain may be
infection, rotational instability, splitting of the frag- acute or insidious in onset, and unilateral or bilat-
ment and creation of a permanent step defect. Palmar eral. The forelimbs are more commonly affected
digital neurectomy is recommended for horses with than the hindlimbs. Unilateral lameness tends to
persistent lameness associated with a fibrous union be more severe and of sudden onset as it is generally
of the fracture; however, it does not provide long- caused by a traumatic injury, while bilateral, low-
term resolution of lameness for horses that develop grade lameness may be more compatible with syno-
OA of the DIP joint. vitis or degenerative disease.

Prognosis Differential diagnosis
Overall, the prognosis for soundness is poor, Acute lameness: collateral desmitis, deep digital
although the reports of internal fixation or extreme flexor tendinitis, fracture, bruising, abscess. Chronic
heel elevation offer some hope for successful return lameness: chronic bruising (pedal osteitis); navicular
to work. disease; chronic laminitis; hoof imbalance.

SYNOVITIS, CAPSULITIS AND Diagnosis
OSTEOARTHRITIS OF THE DISTAL Physical examination findings, except for the
INTERPHALANGEAL JOINT presence of lameness, are usually unremarkable,
although in some acute and chronic cases distension
Definition/overview of the dorsal pouch of the DIP joint may be palpated
Although synovitis, traumatic arthritis and OA on the dorsodistal aspect of the pastern, immediately
occur in the DIP joint, there is considerable debate above the coronary band (Fig. 1.190). Some horses
about the prevalence of pain arising from this joint. can have effusion of the dorsal pouch of the DIP
Confusion arises from the inability to localise pain joint without lameness. Lameness is usually worse
exclusively to the DIP joint with local analgesia, on hard ground and when circled with the affected
the ability to treat injuries of the podotrochlear limb on the inside of the circle. Flexion of the digit