Page 274 - Canine Lameness

246 15 Shoulder Region

Video 15.3

Infraspinatus contracture – gait comparison before and after surgery.

Palpation shows that the humerus is incapable of internal rotation (pronation) relative to
the scapula, because the contracted infraspinatus prevents medial rotation. This can be evalu-
ated by stabilizing the scapula and attempting internal rotation of the humerus/limb.
Alternatively, one may internally rotate the limb without stabilizing the scapula: a patient that
has a contracted infraspinatus will show elevation of the caudal scapula during this maneuver.
The contralateral limb, when normal, provides a good reference point for what internal rota-
tion capacity should be.

15.8.3 Diagnostics
Physical exam findings with mature contractures are unique enough that diagnosis of infraspinatus
contracture is generally convincing on physical examination. Although further advanced diagnostics
are typically not required specifically for the contracture, advanced imaging is beneficial to assess for
other soft tissue injuries as well. For example, radiographs are a reasonable initial diagnostic tool to
screen for other shoulder pathology, yet are expected to be normal with infraspinatus contracture.
In contrast, acute injury of the infraspinatus can be challenging to identify on physical exam.
Ultrasound or MRI is a necessary diagnostic tool if the clinician is suspicious of early infraspinatus
injury and seeks a diagnosis prior to contracture to attempt preemptive therapy to avoid progression
of dysfunction. Ultrasound is the most affordable and clinically relevant imaging tool to confirm a
diagnosis of infraspinatus contracture. MRI is reported to have 100% agreement and concordance
SHOULDER REGION 15.9 Osteochondrosis Dissecans
with surgical findings of infraspinatus disease (Murphy et al. 2008).

Osteochondrosis is a disorder of the endochondral ossification process of developing animals.
Normal endochondral ossification is the process whereby cartilage transforms into metaphyseal or
epiphyseal bone. In osteochondrosis, the transformation into bone is disrupted, leaving a defect in
the interface between cartilage and subchondral bone. Over time, this defect may allow the forma-
tion of a fissure or flap of cartilage over its surface, known as osteochondrosis dissecans (OCD). This
flap can dissociate, which typically leads to joint effusion, synovitis, lameness, and arthritis
(Ytrehus et al. 2007). The most likely site of OCD in the canine shoulder is the caudal surface of the
humeral head, however, it has been reported infrequently to occur in the glenoid cavity (Lande
et al. 2014; Bilmont et al. 2018). In general, surgical removal of the flap (osteochondroplasty) is
recommended for treatment of shoulder OCD, which is associated with favorable outcomes.

15.9.1 Signalment and History
Given the developmental nature of the disease, most clinical symptoms occur early in the dog’s life,
with most animals presenting between 4 and 8 months of age. Large- and giant-breed dogs are most
commonly affected, and high-protein, high-calorie diets have been implicated as an associated