Page 260 - Canine Lameness

232 15 Shoulder Region

rehabilitation, Velpeau slings, or the use of a shoulder stabilization system (“shoulder hobbles”) that
prevent abduction (Henderson et al. 2015). Severe instability such as subluxation and complete luxa-
tion typically require surgery. Surgical options reported comprise thermal capsulorrhaphy, intra-
articular reconstruction, and arthroscopically assisted or open placement of prosthetic ligaments.

15.4.1 Signalment and History

MSI is most commonly seen in middle-aged working dogs with hunting, field trial, or competitive
agility dogs seemingly predisposed. Agility dogs must overcome jumps and A-frames, pass weave
poles, and perform quick turns, which is believed to result in damage to the medial shoulder stabi-
lizers. The reported mean age of affected dogs is four to five years (Cook et al. 2005b; O’Donnell
et al. 2017).
History and clinical signs with MSI consist of varying degrees of lameness and depend on the
severity and time since injury. Clinical signs may be very mild and only noted during performance.
Owners may observe a shortened stride and reduced level of performance, avoiding certain activi-
ties such as quick turns. However, particularly with high-grade MSI, dogs may also show more
severe symptoms such as non-weight-bearing lameness. Typically, lameness is worse after exercise
or heavy work. Further, despite rest and administration of nonsteroidal anti-inflammatories, these
signs often do not improve and return quickly once activity levels are increased.

15.4.2 Physical Exam
Pain and muscle spasm upon regional palpation, atrophy of the shoulder muscles, and restricted
ROM (particularly in extension) are frequently noted upon examination of patients with MSI.
Discomfort upon abduction and increased abduction angles (as identified during the abduction
test; Figure 15.7) are also common but may not always be present.
The abduction test quantifies the degree of abduction of the shoulder. This assessment should be
SHOULDER REGION performed with the patient awake as well as sedated. Although sedation provides the most accu-
rate measurement, evaluating the patient while awake allows the clinician to assess the degree of
discomfort. The latter can be performed with the dog standing or in lateral recumbency. To prop-
erly perform the abduction test, the elbow and shoulder are extended so that the humerus and
spine of the scapula are axially aligned. The center of the goniometer is located over the shoulder
joint. One limb of the goniometer is aligned with the spine of the scapula and the other extends
over the lateral aspect of the antebrachium, placed parallel to the humerus. One hand holds the
antebrachium at the level of the elbow and abducts the shoulder while the other hand holds the
shoulder joint/spine of the scapula. This allows the clinician to ascertain that the shoulder and
elbow joints are both extended; allowing for flexion of either joint will result in an abnormally high
value (Figure 15.7). Abduction is performed until resistance by the soft tissues is detected. The
measured goniometer value (considering straight would be 0) at that point is reported. To avoid
variations based on improper technique, it is important to always perform the abduction test fol-
lowing the same protocol. The frequently referenced normal values are based on a previous study
that evaluated 33 medium to large-breed dogs with clinical MSI and 26 control dogs. The authors
reported mean abduction angles of ~54° in the MSI group and ~33° in the control group (Cook
et al. 2005a). While these values are still used as a general reference, recent work suggests that
there are likely breed variations as well as significant variability between observers (Devitt et al.
2007; George et al. 2017). For example, a recent study in sled dogs (n = 130 shoulders) reported a
median shoulder abduction angle of ~45° in clinically normal dogs (George et al. 2017). This dis-