Page 251 - Canine Lameness

223

15

Shoulder Region

1
Kristina M. Kiefer and Dirsko J.F. von Pfeil 2,3
1 Veterinary Surgery and Sports Medicine Assistance, Research and Tutelage, St. Paul, MN, USA
2 Small Animal Surgery Locum, PLLC, Dallas, TX, USA
3 Sirius Veterinary Orthopedic Center, Omaha, NE, USA

15.1 Introduction and Common Differential Diagnoses

Shoulder disease is becoming a more frequently recognized cause of thoracic limb lameness.
Shoulder pathology can be difficult to localize and distinguishing between elbow and shoulder
pain is a challenge that can frustrate even the most seasoned orthopedists. Osteochondrosis is one
example of a common shoulder disease that is easily identified diagnostically, as radiographs are
frequently sufficient to establish a diagnosis. However, many sources of shoulder pain arise from
soft tissue injuries and show no radiographic pathology. As such, other types of diagnostic imaging
are frequently a component in evaluation of shoulder lameness. If the clinician is struggling to
identify a painful reaction in a dog with a thoracic limb lameness, a neurologic examination
evaluating cervical pain, brachial plexus palpation, and neuromuscular reflexes should also be
evaluated, as root signatures of the thoracic limb are not an uncommon finding.
Figure 15.1 and Table 15.1 outline common differential diagnoses and diagnostic steps for this SHOULDER REGION
region.

15.2 Normal Anatomy and Osteoarthritis

The joint surfaces of the canine shoulder comprise the concave glenoid cavity of the scapula and
the convex surface of the humeral head (Figure 15.2). Shoulder stability depends on a complex
interaction between numerous structures, which can be divided into passive (i.e. static compo-
nents that are unable to contract) and active (i.e. dynamic components that can actively contract)
stabilizers. Passive shoulder stability is provided through appropriate synovial fluid volume, the
concave and convex joint surfaces of the glenoid and humeral head, and the medial and lateral
glenohumeral ligaments (MGL and LGL, respectively; Figures 15.3 and 15.4). These ligaments are
intra-articular structures and act as collateral ligaments of the shoulder joint. Another passive
stabilizer is the joint capsule, which travels from the scapular glenoid to the humeral head. Active
shoulder-stabilizing structures include some of the so-called “(rotator) cuff muscles,” such as the

Canine Lameness, First Edition. Edited by Felix Michael Duerr.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/duerr/lameness