A dislocation occurs when the shoulder ball and socket joint is twisted apart. Usually the head of the humerus dislocates forwards but it can dislocate in other directions. A subluxation occurs if the head only partially slips out and then slips back in. Commonly, dislocations occur after a significant injury in young, active people usually under 30 years old. It is very common in contact sports such as rugby. In older patients, dislocation usually accompanies other injuries such as fractures or rotator cuff tears. One group of patients have abnormally loose shoulders and can dislocate without a significant injury. All of the above conditions can be grouped together as examples of instability.
Most
anterior dislocations happen when the arm is in the throwing position
and a violent force pushes the arm further backwards. It can also happen following a fall onto the shoulder. In
young patients, dislocations usually result in ligaments at the front of
the shoulder being torn off the bone. The point were the ligaments
attach is called the labrum. It
is unusual for this labrum to heal back in its origin site. Poor healing
of a labral tear is the commonest cause for a patient to go on to have
further dislocation. Thus further dislocations occur often after only
minor trauma. Sometimes an injury can result in a small labral tear which does not result in instability but can cause pain and clicking.
When the shoulder dislocates, it should be reduced as soon as possible. Considerable damage to the joint surfaces can occur while the head is out of place. With each further dislocation more damage can happen. Once a patient has had a further dislocation they are highly likely to go on to get more instability. Thus at the Upper Limb Centre it is recommend that patients with recurrent dislocations have surgery to reattach torn ligaments and to repair bankart lesions.
The ligaments and labral tears can be repaired either arthroscopically or by open surgery. The arthroscope is a small telescope that can be placed in the shoulder joint to allow the surgeon to see the structures inside. While watching, the surgeon can place stitches in the torn ligaments and then reattach them back to the bone using mini-anchors inserted into the bone. In some patients, the ligaments are too badly damaged for arthroscopic repair and then an open repair using conventional surgical techniques is recommended. Studies have shown a slightly greater risk of recurrence of the dislocation with arthroscopic repair. The benefits of arthroscopy include reduced scaring; little pain; early discharge; better range of movement and reduced risk of infection.
Whether surgery is open or arthroscopic the patient is kept in a sling for 2 to 3 weeks as per the surgeons instructions. Elbow, wrist and hand exercises are started immediately to prevent secondary stiffness. Gentle range of movement exercises are started from 3 weeks. At six weeks, active movement against resistance is started. More athletic activities can restart after 3 months.
If the shoulder becomes unstable again, it is likely the repaired structures will have stretched out again. In this circumstance open surgery is recommended to re-achieve stability. This open surgery often results in a loss of movement due to shortening of ligaments, tendons and muscles.
