Disorders of the Shoulder in Horses
Shoulder lameness in horses is less common than many owners expect. Although cases are often described as having a typical gait (reduced protraction/cranial phase, wearing of the toe, a swinging lameness), they are still difficult to diagnose simply from analysis of the animal’s walk or trot. However, almost all cases have atrophy of the proximal limb muscles (especially supraspinatus, infraspinatus, the cranial shoulder muscles, and muscles of the cranial antebrachium) beyond that which would normally be expected for lameness caused by distal limb disease. This is associated not with shoulder pathology per se, but is a general feature of proximal limb lameness. Intra-articular anesthesia, medication, and centesis can be accomplished by passing a 90-mm spinal needle between the cranial and caudal parts of the lateral tuberosity of the humerus, angling caudodistally, from above; an ultrasound-guided technique is also described. Radiography is limited to the mediolateral projection, with the limb extended, and in some cases oblique projections (usually caudolateral-craniomedial or proximocranial-proximodistal). Ultrasonography is essential for full assessment of the shoulder region, particularly the soft tissues.