Page 220 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.5 The hindlimb 195

VetBooks.ir TIBIA

Differential diagnosis
FRACTURES
Pelvic stress fractures; stress-related injury of the
Definition/overview distal aspect of the third metatarsal bone; fracture of
Fractures of the tibia include proximal physeal any other bone; septic arthritis.
fractures, fissure fractures and diaphyseal dis-
placed or non-displaced fractures, as well as Diagnosis
stress-related fractures. Distal physeal fractures Diagnosis is based on clinical signs and findings
are rare. on palpation. Some horses with stress fractures
will respond with pain on deep palpation or per-
Aetiology/pathophysiology cussion of the easily palpable medial aspect of the
Stress fractures of the tibia result from an accu- tibia; however, this is not very reliable. Stress frac-
mulation of stress and microfracture at the level tures should be suspected in racehorses when the
of the caudal or caudolateral cortex of the tibia. lameness is pronounced, improves with rest and
These fractures usually occur in 2-year-old recurs after work. Diagnostic analgesia is com-
Thoroughbreds in training and are most com- monly impractical and should be avoided in cases
monly unilateral. Physeal and diaphyseal fractures of acute lameness where a fracture is suspected.
are usually of traumatic origin, either following a Plain radiographs are suitable for imaging of all
kick or as a result of a fall. Proximal physeal frac- displaced fractures; however, some stress fractures
tures are most common in foals, usually following and non-displaced or fissure fractures may ini-
a kick or after being stepped on by the mare. These tially be radiographically silent and only become
fractures originate medially, separating the proxi- evident after 10–14 days. In these horses, bone
mal epiphysis from the metaphysis and propagat- scintigraphy is the most suitable imaging modality
ing laterally across the physis to about two-thirds to aid diagnosis. Increased radiopharmaceutical
the width of the bone where the fracture orienta- uptake can be seen on the affected cortex, usually
tion becomes vertical, commonly forming a Salter– in a single area, but occasionally at multiple sites
Harris type II fracture. Some of these fractures or bilaterally (Figs. 1.375, 1.376).
will be minimally displaced initially, but progres-
sive displacement usually occurs. Most diaphyseal Management/prognosis
fractures are displaced, spiral in configuration and/ Horses diagnosed with stress fractures should be
or comminuted and occur at all ages. box rested for 1 month and then have controlled
walking exercise combined with box rest for an
Clinical presentation additional 2 months before resuming training. The
Horses affected with stress fractures are commonly prognosis for a return to racing is good; however,
presented with acute lameness that improves greatly, introduction of training too early predisposes to
but only temporarily, after a few days of rest. Severe recurrence. Good management prior to referral
non-weight-bearing lameness may indicate an of horses with complete fracture is crucial, as the
incomplete fissure fracture or a complete displaced lack of soft tissue on the medial aspect of the tibia
or non-displaced fracture. Abduction of the affected increases the risk of converting a closed to an open
limb at the level of the tibia occurs if the fracture fracture if adequate immobilisation is not achieved
is displaced and/or comminuted. A wound may be immediately.
present at the injured site and also medially if the Incomplete fissure or non-displaced diaphy-
sharp edges of the fractured bone have penetrated seal fractures should be treated conservatively
the skin. with box rest and cross-tying. As this does not