Acromioclavicular arthritis
X-ray of a healthy shoulder showing the acromioclavicular joint on the top

Definition

Osteoarthritis or arthritis of the acromioclavicular joint is a degenerative condition caused by chronic inflammation, which leads to severe pain and loss of function.

Illustration depicting arthritis of the acromioclavicular joint between the clavicula (collar bone, front) and the acromion (shoulder bone, back

Pathology

Together with the glenohumeral joint, the acromioclavicular joint (AC) is an important joint for the function of the shoulder. The AC joint is situated where the collarbone (clavicle) meets the tip of the shoulder bone (acromion). Various forms of arthritis can affect the AC joint mostly due to wear and tear and chronic inflammation. The pathology of AC arthritis depends on the form of arthritis, which can be divided in three major types:

Osteoarthritis affects ageing adults and is a degenerative condition caused by slow degeneration of the articular cartilage on the bone surface.

Rheumatoid arthritis is a chronic, systemic autoimmune inflammatory disease, which erodes the joint lining or synovium. It usually involves several joints of the body in people of any age.

Post-traumatic arthritis occurs subsequently to an injury to the bone, such as a fracture or dislocation of the shoulder.

Classification

Fractures of the humerus shaft can display various patterns: transverse, oblique, spiral, and comminuted. In addition they are differentiated depending on whether the fracture is displaced or undisplaced, relative to the loss of bone alignment and closed or open fracture. The AO (Arbeitsgemeinschaft für Osteosynthesefragen) Foundation, an international organisation founded in Switzerland, focussing on research and education for the management of orthopaedic injuries), is one of most used systems available to characterise humerus shaft fractures. According to the AO humerus shaft fractures are divided into their level of comminution:

Type A - No comminution

Type B - Presence of butterfly fragment (wedge-shaped fragment of bone

Type C - Comminution

Weight lifting and shoulder overuse is a possible cause of acromioclavicular arthritis

Causes

The main aetiology of AC Arthritis is overuse of the shoulder in ageing individuals and active sportsmen/women. Weightlifters, other athletes or workers who repeatedly lift heavy weight with overhead movement are particularly prone to develop AC arthritis. It can also develop as a degenerative pathology following bone injury. Pre-existing, congenital autoimmune arthritis can include, amongst other joints, the deterioration of the AC joint.

Risk factors

The risk to acquire shoulder osteoarthritis is higher in individuals practicing heavy object lifting, including recreational weight-lifting and professions that involve overhead work . A previous dislocation of the AC joint can also predispose to AC joint arthritis.

Pain when crossing the arm over the chest is typical of an acromioclavicular arthritis

Symptoms

In AC joint arthritis increasing pain progresses over time and is mostly located on the front side of the shoulder joint. It is heightened with the movement of the arm across the chest due to the compression of the joint. It can manifest at rest and during sleep. The range of movement of the shoulder is reduced mostly when lifting the arm over the head. These symptoms can be associated with pain to other joints in rheumatoid arthritis or following major trauma. A bump over the AC joint can also appear. Clicking or snapping noises can be heard during movements.

X-ray showing arthritis of the acromioclavicular joint

Diagnosis

During clinical consultation the medical history of the patient is recorded and followed by the physical investigation. Tests are performed to assess the limitation in the range of movements of the
shoulder by gently pulling the arm of the affected side across the chest. This results in acute pain. Appearance of deformities, swelling, external injuries and tenderness at touch are established. X-ray is the first diagnostic tool to detect cartilage degeneration, presence of bone spurs and associated injuries (fracture of the clavicle or other parts of the shoulder joint). Pain usually disappears when using local anaesthetics.

Treatment

Location of an acromioclavicular joint injection for conservative treatment

Nonoperative treatment

Nonoperative treatment includes rest, application of ice/heat pads, oral administration of NSAIDs and local injection of steroids when the symptoms are significant.

Patient following open surgery for partial resection of the clavicle

Surgical treatment

If conservative treatment is unsuccessful, arthroscopic or open surgery is recommended. Resection arthroplasty aims to remove a fragment of the edge of the clavicle to create more space in the joint and restore mobility.

Temporary immobilisation of the shoulder after surgery

Rehabilitation

Up to four weeks post-surgery, it is advised to use a sling to support the shoulder. Immediately after surgery a gentle physiotherapy can commence to strengthen the muscles around the shoulder and restore joint flexibility. This is followed by tailored exercise program at home.

Shoulder stretching and exercise help preventing acromioclavicular arthritis

Prevention

A number of methods are advised to maintain a healthy shoulder once AC arthritis has been diagnosed and treated. They include the interruption of contact sport activities; restriction of overhead work, weight lifting, and avoidance of extreme arm movements. Prevention is assisted by a regular exercise to keep the muscle tone and shoulder flexibility.