Medial Shoulder Syndrome
What is Medial Shoulder Syndrome?
It is a common cause of forelimb lameness in performance, working and active dogs. The shoulders are not unstable, but instead show evidence of sprain and strain injury leading to discomfort and dysfunction. The injury can involve ligament disruption, tendon damage and tears to the shoulder joint capsule.
What are the Presenting Signs?
Signs can range from refusing to take tight turns with little obvious lameness to total weight bearing lameness. Osteoarthritis may develop if treatment is not carried out and the dog then shows the signs of arthritis.
What is the Cause of Medial Shoulder Syndrome?
Medial shoulder syndrome is believed to be related to chronic sprain and strain as a result of repetitive activity or overuse (such as jump-turn combination and running between weave poles during agitity trails) rather than trauma. Slipping on wet surfaces can also contribute to the trauma that affects the shoulder. Such manouvers put the shoulder near its end range of abduction and therefore stress the soft tissue of the medial shoulder complex. This cumulative effect of trauma occurring to the shoulder structures can lead to discomfort, lameness and performance issues. Overuse of the shoulder support structures can lead to degeneration of the tissues of the medial (i.e. inner side) shoulder hence causing reduced strength and support of these tissues which in turn predisposes them to fraying, disruption and eventually complete breakdown. Once instability, subluxation or luxation occurs, the condition is known as medial shoulder instability.
How is the Condition Diagnosed?
Owners will present their dogs due to a history ranging from avoiding tight turns during performance to intermittent front leg lameness that becomes worse with exercise and heavy activity. These dogs usually fail to respond to both rest and non-steroidal anti-inflammatories.
Affected dogs present with lameness of one fore leg which ranges from a mildly shortened stride at a walk to a significant weight-bearing lameness. There is often reduced shoulder extension, and spasm and discomfort on abduction.
The dog is placed in lateral recumbency with the affected shoulder upmost in position when examining the shoulder. A hand is placed on the side of the shoulder and the elbow and shoulder are moved to full extension, and the forelimb is abducted (i.e. bent sideway). Affected dogs show signs of dysfunction, pain and spasm during this test.
Arthroscope allows direct examination of the major inter-articular structures and can provide a definitive diagnosis of medial shoulder syndrome by showing tearing of the affected structures.
Managing Dogs with Medial Shoulder Syndrome
Dogs with medial shoulder syndrome are divided into three categories, depending on the severity of the injury (which is assessed as a result of the lameness examination, abduction angle tests and arthroscopy of the shoulder),
Mild medial shoulder syndrome
There are only mild change to the shoulder which includes inflammation without disruption or laxity of the medial glenohumeral ligament, subscapularis tendon and joint structure (i.e. all structures on the inside of the shoulder). Surgery is not usually required in this case. Affected dogs are placed in a shoulder support system or hobbles and undergo a rehabilitation therapy program.
Moderate medial shoulder syndrome
Most cases occurring in active or working dogs fall into this category. Arthroscopy of these cases shows disruption or fraying of the subscapularis tendon and medial glenohumeral ligament, and disruption or fraying of the joint capsule. Treatment includes radio frequency induced thermal scarring of the joint capsule, surgical scarring of the inner side of the joint capsule, or stabilisation of the inner side of the joint.
The stiffness of the tissue is greatly reduced two weeks after treatment. The mechanical properties return to near normal by 6 to 12 weeks after the tissues have undergone active repair from the surrounding healthy tissue. During the healing phase post surgery the dog is placed in a shoulder support or hobbles for three months while also undergoing a rehabilitation program. A shoulder strengthening program and preventive maintenance program are also carried out to avoid recurrence.
Prescriptions of anti-inflammatories are not recommended as inflammatory reactions are necessary in the healing process.
Severe medial shoulder syndrome
These are normally injuries. Affected dogs show signs of front and inner shoulder laxity with the shoulder joint bending outwards at greater than 65 degrees. On arthroscopy signs of complete tears to the medial glenohumeral ligament and severe disruption of the subscapularis tendon and joint capsule are often seen. In these cases the inner side of the joint requires reconstruction and this can be schieved surgically by various methods. After surgery the dog is placed in a splint for two weeks followed by a shoulder support system for 2 to 3 months. Rehabilitation therapy is required for 4 to 6 months.