Page 271 - Canine Lameness

15.8 nfraspinatus Disease 243

history. Dogs frequently are reported to have failed medical management therapy and have chronic
intermittent or waxing and waning lameness.

15.7.2 Physical Exam

Patients generally present with a weight-bearing lameness. Pain on direct palpation of the
supraspinatus may be found. Dogs commonly have pain on flexion of the shoulder, since this
stretches the muscle. The entire muscle should be palpated starting with the origin in the supraspi-
natus fossa to the insertion on the greater tubercle. This palpation should be performed while the
shoulder is flexed. Direct palpation of the muscle insertion (i.e. the most common location of
pathology) can be difficult to differentiate from biceps pathology, given their close proximity.
Differentiation between the two conditions may be possible by adding elbow extension to the
manipulation. This maneuver stretches the biceps, which crosses both joints, whereas the
supraspinatus crosses only the shoulder, and thus extension of the elbow should not change the
pain response for supraspinatus pathology.

15.7.3 Diagnostics

Radiographic identification of supraspinatus tendinopathy is only apparent when calcification is
present. In some cases, it can be challenging to determine if the calcification is supraspinatus or
biceps tendon; however, supraspinatus calcification is generally identified more cranial and lateral
than biceps calcification (Figure 15.12). In a recent case series, supraspinatus calcification was
identified in 13% of the cases (Canapp et al. 2016). Radiographs are also useful to rule out other
disease processes such as osseous neoplasia.
Similar to biceps brachii tendinopathy, other modalities used in identifying supraspinatus ten-
dinopathy are ultrasound, MRI, and CT. Ultrasound is the most practical and cost-effective imag-
ing modality. It allows distinction of supraspinatus disease from biceps disease and detects cases
with minor calcification (Mistieri et al. 2012). Ultrasound findings may include increased diam-
eter of the supraspinatus tendon, increased fluid content, and displacement of the biceps tendon
medially (LaFuente et al. 2009; Mistieri et al. 2012). MRI is also an effective means of diagnosing SHOULDER REGION
supraspinatus tendinopathy, with similar abnormalities identified as ultrasound. Tendon volume
can be measured and was consistently found to be larger in affected than normal supraspinatus
tendons (Spall et al. 2016). CT has not been as thoroughly described for this particular disease but
may be useful to rule out other disease processes. Since the supraspinatus is an extra-articular
structure, arthroscopy is generally not considered a primary diagnostic methodology. However,
intra- articular compression of the biceps tendon, termed a supraspinatus bulge, may be observed
(Canapp et al. 2016).

15.8 Infraspinatus Disease

Infraspinatus disease is an uncommon cause of thoracic limb lameness, generally referred to as
infraspinatus contracture, the result of permanent shortening (i.e. contracture not contraction) of
the muscle. The condition manifests in two phases, the acute phase when the muscle is injured and
the chronic phase once contracture has matured. The latter causes a mechanical lameness that
results in a pathognomonic gait (Video 15.2). Animals are generally presented during the chronic
phase. However, this may change with advances in diagnostic capabilities and knowledge about
the disease progression.