Challenging forelimb lameness: the shoulder (Proceedings)
Diagnosing and treating forelimb conditions in dogs can be very challenging. Many dogs present with a similar history including minimal responsive to rest and non-steroidal anti-inflammatory drugs and increased lameness following exercise and heavy activity. It can be difficult to localize the lesion on palpation as many dogs may show increased sensitivity in the shoulder and elbow from referred pain and compensation. To further challenge the veterinarian it is not uncommon for diagnostics such as radiology to be within normal limits due to the soft tissue nature of these injuries (tendon, ligament, and cartilage). Fortunately, with the availability of advanced diagnostics (arthroscopy, MRI, CT scan, ultrasound, etc) the definitive diagnosis can be determined and an appropriate treatment plan created. Depending on the diagnosis (tendon, ligament, cartilage lesions, etc) treatment options may include arthroscopic treatments, stem cell therapy (SCT), platelet rich plasma (PRP), rehabilitation therapy and medical management.
In humans and dogs, several degenerative disorders in the insertion of the supraspinatus tendon have been identified, including rotator cuff tears, calcifying tendonitis or tendinosis, and tendinosis as a result of overuse. Degeneration of the supraspinatus tendon has been suggested to be a factor in the development of rotator cuff tears in humans. Overuse injury has been suggested as the cause of this disorder, and the role of overuse in the pathogenesis has been supported by findings of experimental studies. Histologically, affected tendons contain discontinuous and disorganized collage fibers. Typically, no inflammatory cells are detected. In chronic cases, a proliferative nodule develops which can cause biceps brachii tendon displacement and pain.Dogs commonly present with a history of a chronic unilateral weight-bearing lameness that is exacerbated with activity and often refractory to treatments. Supraspinatus atrophy may be noted and discomfort may be elicited by direct palpation over the tendon and during flexion of the shoulder. It is not uncommon to identify concurrent BT or medial shoulder instability (MSI), therefore a thorough shoulder exam including biceps test and abduction angles are required.
Enhanced imaging using MRI is able to readily visualize the condition in the acute phase. Plain radiography and CT Scan may reveal mineralization just cranial to the greater tubercle in chronic cases. Ultrasound may also a useful modality for diagnosing this condition. Arthroscopic exploration may identify "impingement" of the biceps tendon secondary to supraspinatus tendon swelling as well as possible MSI pathology.
Depending on the severity, treatment options may include rehabilitation therapy (manual therapy, modalities, therapeutic exercise, etc), platelet rich plasma (PRP), and stem cell therapy. In chronic cases, it is necessary to re-initiate the inflammatory process to stimulate the healing response.
Surgical treatment is warranted for those that do not respond to conservative medical management and rehabilitation therapy. Surgical treatment should include arthroscopic exploration to identify and treat concurrent BT and/or MSI if noted, or resection of abnormal tissue through an open approach. Surgery has been considered the treatment of last resort in humans with tendinosis because of the small reported difference in treatment success between surgical intervention and conservative management.
Another common shoulder condition seen in active dogs is bicipital tenosynovitis (BT), which involves the biceps brachii muscle and its tendon that crosses the shoulder joint. The biceps flexes the elbow and extends and stabilizes the shoulder joint during standing or during the weight-bearing phase of locomotion.
The cause of injury in performance dogs appears to be related to repeated strain injury. This includes two-on/two-off contacts, landing vertically on the forelimbs from a misjudged jump, overstretching of the muscle, quick turns, and repetitive contractions of the muscle with the shoulder flexed and/or the elbow extended. Injury to the tendon can occur in a number of ways including strain from overloading, degeneration, or disruption. A single less than maximum load may injure some of the fibers without complete failure of the tendon, but the blood supply to the tendon proper is poor, leading to a longer healing time. Repetitive strain injury may initiate actual degeneration of the tendon. As the area continues to be reinjured, the tendon may weaken sufficiently for inflammation and/or microtears (tendinopathies) in the connective tissue in or around other tendons to form, ultimately leading to shoulder joint instability.
Performance dogs with BT commonly have difficulty with quick turning to the affected side and are reluctant to jump. Agility dogs may also have issues performing two-on/two-off contacts and knocking bars with their forelimbs. On gait analysis, dogs with BT often have a shortened stride and a weight-bearing lameness (subtle to severe) that becomes worse with activity. Pain may be elicited by direct palpation over the biceps tendon. Pain and spasm may be noted when flexing the shoulder while at the same time extending the elbow. Radiographs are of minimal assistance when the injury is in its acute phase, but may reveal mineralization of the tendon when the condition is chronic. MRI (magnetic resonance imaging) and ultrasound may be used to identify the condition in acute and chronic situations. Shoulder arthroscopy is recognized as superior to other diagnostic procedures for diagnosis of bicipital tenosynovitis.