Shoulder pain

Definition

Shoulder pain is any pain felt in or around the shoulder joint.

Anatomy
The shoulder is made up of three bones (humerus, scapula and clavicle) which connect with each other on four joint surfaces. The main joint is that between the scapula (shoulder-blade) and the upper arm (humerus) and is called the glenohumeral (GH) joint. Though commonly referred to as the shoulder joint, this is only one of the four joints.

The GH joint has a wide range of mobility, but the anatomy renders it potentially unstable. It is supported by several surrounding muscles and tendons, the main ones being the glenohumeral ligament, and the rotator cuff, comprising four muscles which form a cuff around the top of the humerus, to which they are attached.

As with all major joints, a cushioning bursa protects the tendons from wear and tear.

Causes
 

Shoulder pain may be caused by injury, inflammation or dislocation of any of the joint components. Problems can generally be ascribed to intrinsic or extrinsic causes, and the patient’s age and type of complaint can be diagnostic.

Important extrinsic causes of shoulder pain which may need immediate attention must be ruled out:

• Neurologic problems like nerve compression in the neck (C5,6,7) or a spinal cord lesion;
• Abdominal: liver disease, diaphragm irritants such as a ruptured organ, injury to the spleen, ectopic pregnancy;
   
• Heart attack, axillary vein thrombosis, thoracic outlet syndrome; or
   
• Pulmonary embolus, pneumonia, or lung tumour.

Intrinsic causes usually lead to stiffness, pain caused by a specific movement, weakness and instability, in any combination.

• Rotator cuff problems as a group predominate
  - weakness or rupture/injury can lead to dislocation of the shoulder
  - tendonitis (inflammation)usually due to repetitive use;
   
• Adhesive capsulitis, known as frozen shoulder;
   
• Osteoarthritis, which is more common in the elderly;
   
• Inflammatory disorders, like rheumatoid arthritis or polymyalgia rheumatica tend to affect both shoulders and are also more common in the elderly;
   
• Thryroid disorders are not a common cause, but either hypo- or hyper-thyroidism may cause shoulder pain;
   
• Impingement syndrome: seen in those with rounded shoulders, poor muscle development, or whose work involves much movement above shoulder level.

Diagnosis
 

The patient’s history is significant, and the general examination should give a clear indication of the problem. If there are no conditions demanding urgent attention (see extrinsic causes) then there should be an examination of the joint proceeds, to assess:

• Obvious fractures, bleeding, injury;
   
• Asymmetry or deformity, including muscle wasting;
   
• Tender spots; or
   
• Range of motion.

Findings are then confirmed by either diagnostic tests (like injecting local anaesthetic, which confirms rotator cuff tendonitis), or by imaging studies such as

• Plain X-rays – most useful in suspected trauma;
   
• Ultrasound – useful for tendon and cartilage tears;
   
• MRI scan – this is the best study for suspected rotator cuff injury, but will also show biceps tendon problems, tumours and other problems of bone; and
   
• Arthroscopy to see the inside of the joint may be of use in frozen shoulder, and may even be used to treat the condition at the same session.

Treatment
 

Treatment in the acute phase of all shoulder pain follows the RICE regime
R rest the joint (immobilise)
I ice is applied
C compress the joint
E elevate the limb – not strictly applied to the shoulder joint, which should rather be kept in a neutral, pain-free position
Once the underlying cause is identified, specific treatment is begun.

Extrinisic causes like polymyalgia rheumatica may need referral to suitable specialists for management.

Intrinsic causes may be managed step-wise, starting with conservative medical management.
Biceps and rotator cuff injuries and tendonitis are treated with rest, limiting overhead positioning of the arm, and encouraging specific gentle exercises.
If there is no improvement after two to four weeks, a short course of non-steroidal anti-inflammatories is begun, or an injection of corticosteroids plus local anaesthetic may be tried. Strict aftercare must be followed after such an injection to avoid permanent tendon damage.
Pain persisting beyond three months despite these measures, is an indication for specialist referral, with a view to surgical repair, which may be arthroscopic or open (conventional surgery).
Tendonitis generally responds well to medical treatment.

Frozen shoulder is treated by gentle exercise to restore the normal range of movement. Most (95 percent) of cases respond well to treatment. Any underlying contributory causes are treated on their own merits.

Impingement syndromes need treatment to prevent tendon damage, and this is achieved by gentle stretching exercises, and those to strengthen the muscles supporting the joint and around the shoulder-blade. Ongoing exercises are recommended for a good outcome.

Dislocated or subluxed joints need to be restored, but there is a high recurrence rate. Surgery may be required to help stabilise the joint.

Fractures may need immediate surgery, though some may be managed conservatively, such as an uncomplicated, stable, simple compacted fracture of the upper humerus.

(Dr AG Hall)