Page 65 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

40 CHAPTER 1

VetBooks.ir Careful examination of these foals is necessary CONGENITAL HYPEREXTENSION OF
NEWBORN FOALS (‘FLACCID TENDONS’)
since this presentation may be part of the ‘con-
tracted foal syndrome’. In the most severe cases
the foal is unable to assume the ‘diving position’ Congenital hyperextension of newborn foals has an
necessary for birth and delivery by caesarean sec- unknown aetiology and pathogenesis and the con-
tion is required. Such foals should be euthanased, as dition may be a physiological variant or a temporary
should those in which carpal contracture is part of failure of the agonist/antagonist muscle balance.
the ‘contracted foal syndrome’. However, provided It is common in premature (<320 days) or dysma-
the foal’s carpus can be passively extended into or ture foals. The condition is more severe if there is
near to its normal position, the prognosis for nor- accompanying systemic illness or inadequate exer-
mal limb conformation is very good. cise. The flaccidity of the flexor tendons is often
Mild cases may resolve with cautious gen- accompanied by periarticular ligament laxity and
tle exercise, avoiding over fatigue of the foal. joint instability. Commonly, both hindlimbs, or
Oxytetracycline may also be useful in such cases. all four limbs, are affected. There appears to be
Foals that are unable to straighten their forelimbs a higher incidence in Thoroughbreds and heavy
rely on forearm muscular contraction to stand and horse breeds. The MCP/MTP and/or interpha-
if allowed too much exercise, the foal’s forearm langeal joints are usually affected. There is often
musculature will become fatigued and start to show dropping of the fetlock and, in severe cases, the
marked tremors or spasm. Treatment with propri-
etary splints, or incorporating a half tube PVC or
fibreglass dorsal splint (extending just proximal 1.70
and distal to the carpus), with heavy bandaging, is
usually effective in straightening the limb within
a few days. Initially, many foals need assistance to
suckle as they find standing unassisted difficult.
Unilateral cases can rapidly develop overuse limb
injuries in the contralateral limb and, sometimes,
severe carpal valgus. In more severe cases, or in
those in which splinting appears ineffective, surgi-
cal release may be attempted. This involves section
of the tendons of insertion of ulnaris lateralis and
flexor carpi ulnaris to the proximal portion of the
accessory carpal bone. Section of the palmar car-
pal fibrocartilage may also be attempted. Failure to
resolve the condition with splinting indicates a very
grave prognosis and euthanasia may be required in
such foals.

CONGENITAL CONTRACTURE
OF THE PERONEUS TERTIUS
MUSCLE

Congenital contracture of the peroneus tertius
muscle is rare. The condition presents as a severe
flexural deformity of the tarsus, often as part of the
contracted foal syndrome. Treatment by resection of Fig. 1.70 Neonatal foal with severe bilateral
the muscle tendon unit has been reported. hyperextension of the distal limb joints (flaccid tendons).