Clean Run Magazine - November 2007 - 74

Focus on Canine Sports Medicine Rotator Cuff Injury in Performance Dogs By Sherman O. Canapp, Jr., DVM, MS, Diplomate ACVS and Ria Acciani, MPT O © DIANELEWISPHOTOGRAPHY.COM ne of the most common forelimb conditions that presents to VOSM in our canine patients is medial shoulder instability (MSI). This condition may be considered similar to a rotator cuff injury in people. Signs of MSI may be as subtle as performance-related problems (such as refusing tight turns) or be as severe as a weight-bearing lameness. MSI involves multiple components of the shoulder joint and requires a thorough orthopedic evaluation and diagnostic tests to confirm the condition. It is important to identify and treat this condition early to obtain the best long-term results and prevent further shoulder instability and osteoarthritic progression. The recommended diagnostic test for this condition is a shoulder arthroscopy. This minimally invasive procedure allows for complete evaluation of the shoulder joint while performing dynamic testing. Most importantly, if MSI is identified during the evaluation, it can be treated at the same time arthroscopically. If arthroscopic treatment is performed, dogs will be placed in a shoulder protection device (hobbles or sling, depending on the severity) to protect the shoulder as it heals. Dogs are then placed in a rehabilitation therapy program over the next few months. Recovery following MSI treatment ranges from four to five months with dogs returning to competition by approximately six months. Anatomy Anatomically, the canine shoulder joint is the least stable joint, relying on soft tissue structures for stability and function. In dogs the glenohumeral joint (shoulder) has the widest range of motion and is capable of movements in any direction, but its primary movements during ambulation are flexion and extension. The glenohumeral joint relies heavily on capsuloligamentous support to provide stability because its anatomic conformation does not provide a stable socket. The humeral head and glenoid cavity of the scapula make up the ball and socket of the shoulder joint. The glenoid provides little coverage of the humeral head. The joint capsule, ligaments, and surrounding muscles and tendons all contribute to the stability of the shoulder. Insult or injury to any portion of the capsuloligamentous support structures can potentially cause shoulder joint pathology resulting in pain and dysfunction. The components that are most commonly affected by MSI include the joint capsule, medial glenohumeral ligament, subscapularis tendon, supraspinatus tendon, and less commonly, biceps tendon shown in Figures 1 and 2. Depending on the severity and chronicity of the instability, the cartilage may also be affected. Pathogenesis Currently, the exact cause of MSI in dogs is unknown, although it is suspected to be related to chronic repetitive activity, or overuse rather than trauma. Overuse of the shoulder support structures leads to Clean Run | November 07 74

Clean Run Magazine - November 2007

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