Page 77 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

52 CHAPTER 1

VetBooks.ir 1.94 ACQUIRED FLEXURAL
LIMB DEFORMITIES

Definition/overview
Acquired flexural limb deformities are a deviation
of the limb in a sagittal plane leading to persistent
hyperflexion of a joint(s) region. They are either con-
genital (see Congenital musculoskeletal abnormali-
ties, p. 34) or acquired (developmental) (see below).
The condition is not due to contracted tendons, but
to a relative shortening of a tendon unit in relation
to bony structures.

Aetiology/pathophysiology
The aetiology is multifactorial and linked to overnu-
trition, genetics, excessive and rapid growth, and pain.
Excessive feeding in predisposed individuals leads to
excess and rapid growth. These factors plus mineral/
trace element imbalances can lead to DOD and pain,
which alter the stance and loading of limbs.
During rapid bone growth the accompanying
lengthening of the tendinous unit is limited due
to the accessory ligaments, and a discrepancy may
Figure 1.94 Dorsopalmar radiograph of the carpus occur leading to the deformity. Pain during physeal
of a foal 2 months after a transphyseal screw has been dysplasia at rapid growth phases or for other reasons
inserted laterally for the treatment of a carpal valgus. (e.g. OCD) may result in altered limb load bearing
and initiate contraction and shortening of the mus-
culoskeletal unit. In adults, true tendon contraction
medial malleolus, taking care to avoid the articu- can occur post severe tendon injuries. In very pain-
lar surface, which is quite close. ful limbs in any age of animal, chronic non-weight
Whenever transphyseal bridges are used, the foal bearing can lead to flexural deformities, especially
must be carefully monitored after surgery as there is acquired carpal contracture. Typically, this is seen
a risk of overcorrection, converting a valgal to a varal in conservatively managed displaced ulnar fractures.
deformity, or vice versa. Restricted exercise is main- Unless the primary condition can be corrected, the
tained and postoperative radiographic monitoring prognosis for athletic function is usually poor; how-
recommended. The optimal time for screw removal ever, affected horses may be able to survive if the
is just before the limb is completely straight, as fur- contracture is not too severe.
ther straightening will occur for a short time after
implant removal (Fig. 1.94). Clinical presentation
The condition develops after birth through to
Prognosis 2 years old and is commonly seen in the forelimbs
The prognosis is good if cases are managed early at either the DIP (coffin) joint or MCP (fetlock)
and regularly monitored. It is guarded if there is a joint. There is no sex predisposition and unilat-
poor initial response to conservative treatment, if eral and bilateral cases are seen. Acquired flexural
the condition is severe from the outset, concurrent deformity of the DIP joint is typically recognised
problems are present (e.g. contralateral limb lame- between 3 and 18 months and MCP flexural defor-
ness) or if there is rapid deterioration. mity between 9 and 18 months. Clinical signs of