Shoulder arthritis

The shoulder joint (glenohumeral joint), is the most mobile joint of the human body and it allows the arm to move in all directions required for the activities of daily living. It is formed by the head (ball) of the humerus on the one side, and glenoid (socket) on the other. Both surfaces are lined with smooth cartilage that minimizes friction during shoulder movement. Similar to all joints, the shoulder joint has a capsule and it contains a small amount of fluid that further minimizes friction.

Arthritis means progressive cartilage damage (“wear and tear”) causing joint pain and stiffness. Shoulder arthritis is not as common as hip and knee arthritis because it is not a weight-bearing joint. There are various types of shoulder arthritis:

Primary osteoarthritis

This type of arthritis has no obvious cause. It is more common in women and patients older than 60 years old. Younger patients can develop osteoarthritis when large loads are frequently placed on the shoulder (manual labour, contact sports, and weight lifting).

Rotator cuff arthritis/arthropathy

The rotator cuff is a group of muscles around the shoulder that keep the humeral head centred against the glenoid (socket) during shoulder movement. Certain rotator cuff tears cause a muscle imbalance around the shoulder leading to upward migration of the humeral head and eventual rotator cuff arthritis.

Inflammatory arthritis

Rheumatoid Arthritis and SLE are auto-immune disorders that cause inflammation of the joint lining (synovium) and progressive cartilage destruction. Gout is another type of inflammatory arthritis characterized by crystals within the joint.

Post-traumatic osteoarthritis

Fractures that involve the shoulder joint can eventually lead to shoulder arthritis especially when they heal in a displaced position.

Post-instability osteoarthritis

Repetitive shoulder dislocations cause progressive cartilage damage and can lead to osteoarthritis.

Post-infective osteoarthritis

Cartilage can be damaged during joint infections (septic arthritis), especially when treatment is delayed.

Osteonecrosis / avascular necrosis

Various conditions can disrupt the blood supply to the humeral head with the subsequent collapse of the dead bone and irregularity of the humeral head causing further osteoarthritis.

Presentation

Patients with shoulder arthritis typically complain of shoulder pain that developed gradually. The pain is deep-seated and occurs with certain shoulder movements. A grinding sensation may be felt when there is bone-on-bone contact.

Pain is also present at night when sleeping on the affected shoulder. Shoulder arthritis leads to progressive shoulder stiffness which eventually causes functional impairment. Patients with inflammatory arthritis can have episodes of warm swollen joints that are intensely painful.

Diagnosis and work-up

The shoulder range of motion is typically reduced and painful at extremes of movement. In advanced cases, a grinding sensation (crepitus) is felt and heard during shoulder movement. Shoulder X-rays show loss of joint space and other signs of arthritis.

An ultrasound scan is performed to assess the rotator cuff tendons. When a shoulder replacement is considered, a CT scan will be performed to assist with surgical planning. Dr Grey uses 3D planning software to assess the bony anatomy of the shoulder and to plan the joint replacement surgery (see image above).

Non-operative management

Patients with mild shoulder arthritis are initially treated conservatively. Treatment is focused on pain management as well as maintenance of shoulder range of motion.

Options include:

• Simple pain-killers
• Anti-inflammatory medication
• Intra-articular cortisone injections: These are best administered under ultrasound guidance to enhance the accuracy of the injections.
• Physiotherapy

Surgical management

Surgery is considered in more advanced cases of shoulder arthritis or in patients with mild osteoarthritis where non-operative treatment failed to improve pain and function. Different surgical options can be considered:

Arthroscopic (key-hole) joint preserving surgery

This is a good option in younger patients with mild osteoarthritis, and in very active patients where shoulder replacement needs to be delayed. The thickened shoulder capsule is removed to improve shoulder movement. The bony prominence (osteophyte) that is typically present below the humeral head is shaved away and any loose bodies that may be present in the shoulder joint are removed.

The biceps tendon (long head of biceps) is usually released (tenotomy) or fastened onto bone (tenodesis) as it is often inflamed or torn and can be a significant source of pain. An acromioplasty is performed if there is evidence of impingement and the end of the collarbone may be shaved away (AC joint excision) if there is pain arising from an arthritic AC joint.

Most patients have significant pain relief and functional improvement following surgery, but the improvement may only be temporary seeing that osteoarthritis is still present after the procedure.

Shoulder replacement surgery

In advanced cases of shoulder arthritis where there is bone-on-bone contact, a shoulder replacement may be required. There are different types of shoulder replacement surgery.

Hemiarthroplasty

This implies that the head of the humerus is replaced but the glenoid (socket) is not. This is sometimes performed in young, very active patients with advanced arthritis, especially when the glenoid is not suitable for an anatomical total shoulder replacement. The problem with hemiarthroplasty is the ongoing erosion of the glenoid by the metal prosthesis.

Anatomical total shoulder replacement (see image)

This is the gold standard shoulder replacement surgery. Both the humeral head and the glenoid are replaced.

It provides better pain relief and shoulder movement than a hemiarthroplasty.

For an anatomical total shoulder replacement to function, the rotator cuff has to be intact. When a rotator cuff tear is present, the shoulder is not balanced, leading to gradual loosening of the glenoid component. In these patients, a reverse shoulder replacement should be considered.

Reverse shoulder replacement (see image)

Both the humeral head and the glenoid are replaced, but the sphere is placed on the glenoid and the socket onto the humerus.

A reverse shoulder replacement relies on the deltoid muscle to function.

This type of shoulder replacement is indicated for patients with rotator cuff arthritis, patients with severe glenoid bone-loss that prevent an anatomical shoulder replacement from being performed, and elderly patients with complex displaced proximal humerus fractures.