Page 262 - Canine Lameness

234 15 Shoulder Region

15.4.3 Diagnostics
As mentioned above, the shoulder abduction test may result in a tentative diagnosis of MSI, but
advanced imaging is necessary to confirm this diagnosis. The diagnostic modalities of choice
include ultrasound, magnetic resonance imaging (MRI), and arthroscopy, or a combination of
these. Radiographs and CT can be used to rule out other diseases.
Currently, orthogonal survey radiographs of the shoulder are mainly recommended to rule out
diseases that are easily detected radiographically (such as primary bone tumors). Dogs with MSI
frequently show no radiographic abnormalities and therefore radiographs are not very sensitive to
help diagnose MSI (or other soft tissue pathology of the shoulder). Notably, one study in particular
found up to 45% of shoulder radiographs to be normal despite severe intra-articular or periarticular
disease, such as synovitis, MGL disease, SST inflammation, or tears (Bardet 1998). The most com-
monly seen radiographic abnormality in dogs with MSI is mild osteoarthritis (Figure 15.8). On the
other hand, radiographs have recently been suggested as a more objective means of measuring
shoulder abduction angles. One cadaveric study described a technique aiming to provide a stand-
ardized radiographic measurement for shoulder abduction angles, using a specific positioning and
a restraint device (Livet et al. 2018). Clinical evaluation of this technique has not been described
yet but it may become a clinically valuable tool to help diagnose MSI in the future. Because of the
low sensitivity of radiographs to detect MSI, advanced imaging such as musculoskeletal ultra-
sound and/or MRI should be considered to establish a diagnosis.
Magnetic resonance imaging is a sensitive imaging modality for canine shoulder conditions that
allows for evaluation of the entire joint and surrounding structures. Unfortunately, MRI typically
requires full anesthesia, is time-consuming, and is costly. Recent developments in MRI technology
will likely facilitate the development of shorter protocols that can be performed under sedation but
currently, MRI is not a routine diagnostic for detection of MSI at the authors’ institutions. However,
particularly in diagnostically challenging cases or if involvement of the spinal cord, regional
nerves, and the brachial plexus is suspected, MRI is strongly recommended.
SHOULDER REGION lateral muscles and tendons which are easily accessible. The medial compartment of the shoulder
Ultrasound is frequently used to assess the soft tissue structures of the shoulder, particularly the

(C)
(A)
(B)
(D)

(E)

Figure 15.8 Diagnostic imaging techniques of a dog diagnosed with medial shoulder instability (MSI):
(A) lateral radiograph showing minimal osteoarthritic changes; (B) MRI (sequence: Dorsal Proton Density)
illustrating typical thickening along the medial aspect of the shoulder joint (white arrow), at the
attachment of the medial glenohumeral ligament (MGHL) and subscapularis; (C) a normal shoulder MRI of
a different patient for comparison; (D) ultrasound images showing thickening and ill-defined MGHL and
subscapularis (white arrow); and (E) arthroscopic image showing tearing of the MGHL (black arrow).