The shoulder joint is the most mobile joint in the body and is therefore the one most prone to instability.
Types of instability are:
Subluxation: Partial dislocation of the joint. The ball slides partially out of the socket, but never truly dislocates. Dislocation: Complete displacement of the ball out of the socket.
Direction of Instability
Anterior: This is the most common form of instability, and means that the shoulder comes out the front. This accounts for 95% of all instability.
This means that all of the shoulder ligaments are loose, and the joint is unstable in more than one direction. Typically, the shoulder will be unstable anteriorly (front) and inferiorly (down), but a posterior direction may also be involved. This type of instability is sometimes seen in swimmers and other upper extremity repetitive motion athletes. Posterior: Out the back. This type of instability is most rare, and typically occurs with seizure disorders, or unusual trauma.
Patients with subtle forms of instability will only occasionally complain of a feeling of instability. More often the subluxation episodes cause pain or a feeling of numbness in the arm. Diagnosis depends on the history and physical examination by a shoulder expert. Cases of complete dislocation are easier to diagnose. Typically the patient will have had to go to an emergency room to have the shoulder reduced, and an x-ray will be taken which confirms the shoulder having come out of socket. These patients complain primarily of instability, particularly with the arm in the overhead position.
Treatment depends on the severity of the instability and the age of the patient. The younger the patient, the more likely the shoulder will continue to redislocate. Repeated dislocations can severely limit activities and are thought to lead to possible degeneration of the joint. Studies have shown that immobilization and strengthening have minimal influence on the prognosis. The only way to predictably limit the risk of recurrent dislocation is surgical. Current recommendations are to repair the torn ligaments for recurrent dislocations, and to consider surgery even for the first time dislocation in the very young athletic population.
Arthroscopic Bankart Repair
Almost all types of instability can currently be treated arthroscopically. If the ligaments are completely torn, they can be reattached using small tacks placed arthroscopically, without a need for an incision (Bankart Repair). Current methods have been shown to provide approximately a 90% success rate in preventing redislocation.
If the ligaments are stretched, but not torn, there are several exciting new arthroscopic methods for tightening these ligaments. Either sutures can be placed to tighten the ligaments, or the ligaments are heated, which shrinks the tissue causing the ligaments to tighten. Both methods are performed arthroscopically without incisions.
A sling is worn for three weeks. Early range of motion is begun. Over shoulder reaching is limited for 6 weeks. Strengthening is progressive, including a slow return to throwing activities. Full return to contact sports is not allowed for 6 months.
Without surgical treatment most patients will continue to suffer episodes of instability. With surgery, 90% of patients will never redislocate and will be able to return to all sports activities.