300 Canine Sports Medicine and Rehabilitation
modalities, and hydrotherapy. NSAIDs
and pain medications can be prescribed
postoperatively.
When treated surgically, shoulder OCD gen
erally has an outstanding prognosis. Chronic
long‐term cases and dogs that have significant
osteoarthritis may benefit from intra‐articular
injections of hyaluronic acid, PRP, or stem cell
therapy.
Infraspinatus myopathy
Infraspinatus myopathy is normally seen in
large‐breed dogs, particularly working dogs
that do hunting or herding and other very
active dogs (Pettit, 1980). Although it remains
an uncommon occurrence, contracture of the
infraspinatus muscle is one of the two most fre
quently reported contractures in dogs, along
with quadriceps contracture (Fossum, 2002;
Harasen, 2005). The classic presentation of the
contracture is unilateral, but there have been
bilateral cases reported (Leighton, 1977; Slatter,
1985; Dillon et al., 1989). Most present with an
acute onset of shoulder lameness with work or
exercise (Leighton, 1977; Slatter, 1985; Carberry
& Gilmore, 1986; Dillon et al., 1989; Denny, 1993;
Siems et al., 1998; Fossum, 2002).
Cause
Repetitive microtrauma, blunt trauma, and oste
ofascial compartment syndrome have been
reported to cause infraspinatus contracture
(Pettit et al., 1978; Matava et al., 1994). Early treat
ment is focused on surgical decompression by
fasciotomy; however, if contraction has already
occurred, tenectomy or myectomy may be neces
sary (Carmichael & Marshall, 2012; Rochat, 2012).
The hypothesis that an acute traumatic event
with an incomplete rupture of the infraspinatus
muscle may lead to fibrosis and contracture is
supported by the histological findings of degen
eration and atrophy of skeletal muscle with
fibrous tissue replacement (Carmichael &
Marshall, 2012; Rochat, 2012).
Diagnosis
The patient may present with a painful, non‐
weight‐bearing shoulder lameness. The shoul
der may be swollen. The initial pain and
lameness usually resolve with rest and/or
supportive treatment over a period of 1–4
weeks; however, signs of contracture may
appear within several days to weeks after the
initial trauma (Carberry & Gilmore, 1986). The
initial injury to the infraspinatus muscle is not
commonly recognized.
Affected patients typically present with no
signs of systemic illness. With a mature con
tracture, adhesion of the tendon of insertion
of the infraspinatus muscle to the adjacent
joint capsule occurs. Patients have a weight‐
bearing lameness with circumduction of
the affected thoracic limb and a characteristic
flip‐like action of the foot when placing the
foot (Slatter, 1985; Carberry & Gilmore, 1986;
Dillon et al., 1989; Denny, 1993; Siems et al.,
1998). The affected thoracic limb is held with
the shoulder in abduction and the elbow in
adduction against the thoracic wall (Siems et
al., 1998). The distal thoracic limb and carpus
are externally rotated and held in abduction
(Slatter, 1985; Carberry & Gilmore, 1986). The
patient typically is not painful on palpation
and manipulation of the limb (Carberry &
Gilmore, 1986; Siems et al., 1998). The remain
ing shoulder muscles, primarily the supraspi
natus and deltoid muscles, display disuse
atrophy or may be contracted (Carberry &
Gilmore, 1986; Dillon et al., 1989; Denny,
1993; Fossum, 2002). A significantly decreased
range of motion will be noted in the shoulder
(Carberry & Gilmore, 1986). When the patient
is placed in lateral recumbency with the
affected limb up, a true infraspinatus contrac
ture will cause the distal thoracic limb to
remain in an abducted and externally rotated
position off the floor and away from the body
(Carmichael & Marshall, 2012; Rochat, 2012)
(Figure 12.6).
Siems and colleagues (1998) reported a series
of ultrasonographic findings of simultaneous
bilaterally traumatized infraspinatus muscles
in one dog. One muscle resolved without any
complications, while the other progressed to
contracture (Siems et al., 1998). The ultrasono
graphic description of a contracted infraspina
tus muscle is that of increased echogenicity
when compared with the normal muscle
(Slatter, 1985; Denny, 1993). MRI may be use
ful for diagnosing the condition in both the
acute and chronic phases.