Page 686 - Adams and Stashak's Lameness in Horses, 7th Edition

652 Chapter 5

notch of bone, it is thought that the nerve is decom- eral shoulder region can also cause fractures of the spine
pressed, allowing for reinnervation. Complications of of the scapula. 30,37 The California racing population
VetBooks.ir arising from the site of the notched bone. tained scapular fractures while racing or training. There
reported 73 Thoroughbreds and 28 Quarter horses sus-
the surgery include the possibility of a glenoid fracture
was a predominance of male horses and right shoulders,
Prognosis and the injury occurred early in their careers. Quarter
horses appeared to sustain the injury more frequently.
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The prognosis for return to soundness in horses with
suprascapular nerve injury is favorable for both con- Clinical Signs
servative and surgical treatments. In one report 7 of 8
horses with suprascapular nerve injury treated conserv- Horses frequently present with a history of trauma
35
atively were able to return to their intended use. All and signs of lameness ranging from mild to non‐weight‐
eight initially had pronounced shoulder joint instability bearing. 3,9,40 Horses with an acute fracture of the scapu-
during weight‐bearing, and joint stability returned lar spine usually exhibit focal swelling, will bear weight,
within 3–12 months. The conclusion was that rest alone and usually exhibit a mild to moderate lameness at exer-
carries a good prognosis for recovery of a normal gait cise (Figure 5.60). Deep palpation over the fracture site
and return to performance; however, the recovery period usually elicits a painful response.
may be prolonged. Evidence of penetrating wounds may be present.
A high percentage of surgically treated horses are Chronic cases of scapular spine fractures may present
expected to return to performance. In one report 18 of with a draining tract or a history of the development of a
20 horses with suprascapular nerve injury returned to recurrent draining tract as a result of a penetrating
soundness. An important and severe complication wound and sequestration of bone fragments. 9,37 Horses
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associated with the surgery is the postoperative occur- with fractures of the body or neck of the scapula are
rence of fracture of the SGT and complete subluxation
of the SH during anesthetic recovery. Horses that
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develop severe atrophy of the supraspinatus and
infraspinatus muscles prior to surgery may not regain
normal muscle mass, and some atrophy will remain in
the proximal one‐third of the scapula.

FRACTURES OF THE SCAPULA
Fractures of the scapula are uncommon in horses. This
is in part due to the scapula’s proximal location, its close
proximity to the ribs, and the large protective muscle
mass overlying the region. Although scapular fractures
3
occur in all ages and breeds of horses, young (less than 4
years) intact males appear more prone to sustain the frac-
ture. Fractures of the scapula in racing Thoroughbreds
3
and Quarter horses have been extensively described. The
incidence is low at 0.39 and 0.98/1000 starters, respec-
tively. In another recent study evaluating fatal musculo-
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skeletal injuries in racing Quarter horses, scapular
fractures accounted for 8% of the injuries. 83
Fractures of the scapula can involve the spine, SGT,
body, neck, and glenoid cavity. Of these, fracture of the
SGT is most common. Although simple scapular frac-
tures are most common, comminuted fractures also
occur. Bone sequestra may also develop following frac-
tures of the scapular spine, particularly when a penetrat-
ing wound results in a comminuted fracture. 9,37 Stress
fractures of the scapula have been recently described in
28
Thoroughbred racehorses. A high incidence of supras-
capular nerve injury occurs following fractures of the
neck of the scapula. Injury to the subscapularis nerve
and brachial plexus is a rare complication associated
with fractures of the scapula.

Etiology
Scapular fractures are usually caused by direct trauma Figure 5.60. Prominent swelling (arrow) located over the lateral
or following falls during racing or jumping. 30,37 Scapular right shoulder region of a young horse with a complete fracture of
fractures resulting from racing or race falls at high speeds the body of the scapula. The foal was lame at the walk and carried the
tend to be comminuted. Penetrating wounds to the lat- limb further axially than normal. Source: Courtesy of Dr. Gary Baxter.
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