Supraspinatus and biceps tendinopathies are two tendon pathologies of the shoulder that often go hand in hand. After doing a Research Refresh (members only) on the impact of extracorporeal shockwave therapy on these two conditions, I decided to delve into the conditions a bit further.

Now I am not sure if you have the new textbook from VAHL, but I am loving it! Apart from the research paper I reviewed, that is where I got the majority of the information for this blog.

Shoulder Anatomy

The shoulder joint is a simple spherical synovial joint between the glenoid cavity of the scapula and the head of the humerus. The joint capsule extends into the bicipital groove and forms a synovial sheath around the tendon of origin of the biceps muscle. The biceps tendon is kept in place by the transverse humeral ligament. The shoulder joint can move in flexion, extension, abduction and adduction through quite a wide range.

The biceps brachii originates in the supraglenoid tubercle of the scapula, passes through the intertubercular groove, and inserts on the medial and proximal aspect of the radius on the radial tuberosity and the ulna. It acts as an extensor of the shoulder and a flexor of the elbow.

The supraspinatus muscle originates in the supraspinatus fossa of the scapula and inserts on the greater tubercle of the humerus, placing it in a position where it can impinge on the biceps brachii. The supraspinatus muscle is responsible for extension and stabilisation of the shoulder joint.

Canine Rehabilitation and Physical Medicine, Fig 5-17, Page 57 

Presentation

These conditions seem to be overrepresented in large-breed dogs that lead an active lifestyle.

A supraspinatus injury often presents as an already chronic injury to the tendon at its insertion on the greater tubercle. There will be pain on direct palpation of the tendinous insertion. It often occurs bilaterally and concurrently with an injury of the biceps tendon, or changes in the elbow joint. While the opposite shoulder is often affected by supraspinatus tendinopathy, it may be asymptomatic. Pain may be elicited through manipulation of the shoulder, especially into shoulder extension.

A biceps tendinopathy will be painful when the shoulder is hyperflexed and the elbow hyperextended. On palpation, the biceps tendon may also be nodular, palpably thickened, or have a spongy feeling. Direct pressure over the tendon will elicit a pain response.

Dogs will generally exhibit a chronic intermittent weightbearing forelimb lameness that worsens with exercise in both of these conditions.

Cause

The exact cause is unknown, but the literature suggests that chronic overuse injuries are the main suspects. The occurrence of this injury in large-breed active or sporting dogs seems to support this.

An initial injury to the supraspinatus tendon can occur as a result of a direct impact over the muscular insertion that fails to heal due to the continuous load bearing nature of the structure. Biceps tendinopathies can be caused by impingement and compression from an enlarged and already pathological supraspinatus tendon.

There may also be an aspect of degeneration of the tendinous insertion due to ageing. Additional factors may include the occurrence of a joint mice entrapment secondary to osteochondritis desicans, and the occurrence of hypoxia secondary to hypovascularity of the affected tendon.

Diagnosis

A diagnosis can be made through a combination of a clinical exam and imaging techniques. Radiography can reveal mineralisation of the supraspinatus or biceps tendon, and active bony changes on the supraglenoid tubercle. Ultrasound can reveal tendon thickening, irregular fibre patterns, effusion of the biceps tendon sheath, and a defect at the insertion site of the biceps tendon. Arthroscopy can help differentiate suprascapular and biceps tendon lesions, and is useful in assessing the biceps tendon. An MRI is considered the gold standard in diagnostics.

Treatment

Conservative treatment with NSAIDs is indicated only in acute case presentations, as chronic cases will lack the necessary signs of inflammation, leaving NSAIDs less effective. Regenerative medicine with PRP or stem cells can be indicated. For biceps tendinopathies, inter-articular cortisone injections can be successful. Shockwave therapy is showing some promise in the treatment of this condition and is being more regularly utilised. Chronic cases can be highly challenging to manage conservatively, with or without physiotherapy, and can carry a poor prognosis.

If conservative management fails, surgical management is the next step, and is aimed at excising the diseased portion of the supraspinatus tendon longitudinally near its insertion on the greater tubercle, or releasing the proximal biceps tendon from its origin on the supraglenoid tubercle.

Drawbacks of Conservative Management

NSAIDs can play a role in management if administered in the acute phase of the injury, when an active inflammatory process is occurring. As most of these cases are presented in the chronic phase, NSAIDs may hold more risk of side effects than benefit for pain relief.

Intra-articular cortisone injections in cases of biceps tendinopathy also carry some risk, as the articular cartilage can be negatively impacted and osteoarthritis accelerated.

Prognosis

Supraspinatus tendinopathies are hard to treat and have a very guarded prognosis. Chronic cases are generally unresponsive to physiotherapy and conservative management.

Biceps tendinopathies have a good long-term prognosis, but a return to full sport can be affected.

Alternative Treatment Modalities

Regenerative medicine with PRP and stem cells, as well as shockwave therapy should be considered. Initial studies on shockwave therapy for these tendinopathies have shown promise, and the therapy should be further investigated and considered as a treatment option for chronic lesions.

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