Canine Shoulder Disease

      The canine shoulder is a complex joint, with numerous passive and active soft tissue stabilizing components.  Both traumatic and chronic overuse resulting in soft tissue injuries of the shoulder are common causes of lameness, particularly in sporting and hunting breeds.  Determining the specific causes of shoulder lameness is often challenging; standard radiographs provide only limited diagnostic information.  Magnetic resonance imaging (MRI), however, can provide a more complete look at important canine soft tissue shoulder structures.  MRI is a non-invasive diagnostic modality that provides a high contrast, multi-planar depiction of joint associated anatomy. Superior soft tissue image resolution, along with the ability to image in multiple planes, has made MR imaging the diagnostic modality of choice for numerous joint pathologies in human medicine.  We are interested in evaluating the effectiveness of MR imaging in identifying tendon and ligament injuries in the dog shoulder.  We have developed an atlas of the normal structures seen in the dog’s shoulder with MRI and have begun to directly apply this information to our clinical cases.  

Figure 1 is from the MRI atlas of dog shoulder anatomy.  Figure 2 shows the MR image of a clinical patient with contrast material in the joint.  This technique allows us to more closely evaluate the integrity of specific ligaments and tendons.  MRI demonstrated that this patient had a tear in the medial glenohumeral ligament (#3). This was surgically repaired.

Figure 1.  Canine shoulder in the sagittal plane.  (A) T1- weighted, T2*- weighted gradient echo (GE), Proton Density Fat Saturation (PD) and gross pathology section.  (B) Proton Density Fat Saturation MRI and diagram depicting slice locations.  Slice location A refers to the images in Figure 1A; slice location B refers to the images in Figure 1B. 1. Supraspinatus tendon,  2. Biceps tendon,  3.  Humerus,  4. Scapula,  5. Infraspinatus tendon,  6. Acromion,  7. Scapular spine.

Figure 2. Gross pathological section from a normal cadaver and MRI arthrogram of a clinical patient  Both shoulders are seen in the cranial-caudal plane.  The MR image is a T1-weighted fat saturation sequence. 1. Scapula, 2. Subscapularis tendon, 3. Medial glenohumeral ligament,  4. Humeral head,  5. Lateral glenohumeral ligament, 6. Acromion,   7. Infraspinatus tendon.  In image B the medial glenohumeral ligament is torn as evident by its undulating pattern.  This was confirmed with arthroscopy.