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Shoulder Instability

by dr kalman piper

What Is Shoulder Instability?

The shoulder is a ball and socket joint; however the socket is very shallow, allowing a large range of motion of the shoulder. Shoulder instability is the term used to describe the ball slipping out of the socket, and includes shoulder dislocation treatment (where the ball completely slips out of the socket – and usually stays there), and shoulder subluxation (where the ball partially slips out of the socket – and usually pops back in by itself). Shoulder instability can be anterior (most common), where the humeral head slips out the front of the socket, posterior (out the back of the socket) or multidirectional.

What Causes Shoulder Instability?

Shoulder instability is usually associated with an injury to the shoulder, although some people who are ligamentously lax (“double jointed” or extremely flexible) may have problems associated with shoulder instability, without a history of injury to the shoulder. Shoulder instability is a common sports injury, especially in contact sports such as football; skiing and surfing.

Shoulder Anatomy And Pathology

The shoulder joint ball is called the humeral head, and the socket is called the glenoid. Surrounding the glenoid is a tough ring of fibrous tissue called the labrum. The labrum helps stabilise the shoulder joint and prevent the head dislocating, while still allowing freedom of movement. When shoulder instability occurs, the labrum is often torn from its attachment to the glenoid. This is known as a Bankart lesion. This is a very common finding after any shoulder instability event. Other structures that can be damaged include the joint cartilage, the humeral head (Hill Sacks Fracture), the glenoid, ligaments surrounding the shoulder joint, the rotator cuff tendons, and the nerves that supply the arm.

Can Shoulder Instability Recur?

Recurrent shoulder instability is very common. The risk of recurrence is affected by several factors including age, sex, functional demand (sports), number of previous dislocations and previous treatment received. Also, the greater the greater the damage to the shoulder during the first dislocation, the higher the risk of recurrent shoulder dislocation treatment. Despite advances in physiotherapy and shoulder rehabilitation, recurrence rates in active young males is greater than 80%. Even in patients with lower functional demand, recurrence rates maybe as high as 40%.

How Is Shoulder Instability Assessed?

All cases of shoulder instability should be medically assessed, to quantify the extent of the damage to the shoulder joint and surrounding structures. Assessment includes and clinical examination, x-rays and usually an MRI scan. If there is extensive damage to the bones (glenoid or humeral head) then a CT scan may be required as well. An ultrasound scan is not usually helpful in assessing the shoulder after dislocation.

How Is Instability Treated?

There are several treatment options available for shoulder instability. These include:
The best treatment choice will be determined by several factors including extent of the damage to the shoulder and in particular bone abnormalities, other associated injuries to the shoulder, your functional (sporting) demand and your age. Thorough pre-operative assessment is critical to determine the best treatment option for your shoulder.

What Is The Recovery Time From A Surgery?

Rehabilitation and recovery time will depend on the type of shoulder instability, the extent of the damage and treatment received. Generally, most surgeries require 6 weeks in a sling, which allows time for the labrum to heal back to the bone. During this time passive exercises (movement, without using the shoulder muscles) are performed to prevent excessive shoulder stiffness. After the labrum has healed to the bone, the sling can be removed and active exercises can commence. Exercises should never cause excessive shoulder pain.

What Are The Risks Associated With Surgery?

As with any surgery there are associated risks. The risks also depend on the treatment you have received and the extent of the damage. In general, complications related to shoulder stabilisation include:
  • Post operative shoulder pain and swelling, including bruising down the arm.
  • Shoulder stiffness
    1. Most patients have a period of stiffness after surgery and after 6 weeks in a sling. The stiffness improves with physiotherapy, once it commences. Some patients may notice a loss of external rotation of the shoulder, after the Latarjet procedure; however this will not cause any functional loss.
  • Recurrence of the dislocation.
    1. Shoulder stabilisation reduces the risk of recurrent dislocation, but not to zero.
    2. The risk of recurrent dislocation after Bankart repair may be as high as 15%, in young active males, compared to greater than 80% in non-surgically treated shoulders.
  • Loss of throwing strength and delay or inability to return to sports
    1. In general, it takes 6 months to return to sports, however full throwing strength can often take longer to recover (one year or longer).
  • Shoulder Arthritis
    1. Damage to the cartilage of the shoulder joint which occurs with shoulder dislocation treatment predisposes the shoulder to developing arthritis. Unfortunately, surgery cannot reverse any damage to the shoulder joint cartilage, however stabilizing the shoulder may prevent the cartilage damage from worsening during recurrent dislocations.
  • General Surgical Complications
    1. Nerve injuries – stretching of nerves during the shoulder dislocation treatment (most common) or the surgery may cause numbness or muscle weakness in the arm. Most nerve palsies are temporary.
    2. Infection – very rare with arthroscopic shoulder surgery.
    3. DVT – very rare with surgery of the upper limb.
    4. Allergic reactions to anaesthetic drugs or pain medications.
    5. Anaesthetic Complications – discuss with your anaesthetist.