Shoulder Instability
The shoulder is a ball and socket joint. The ball (head of the humerus) sits in the socket (the glenoid fossa).
The socket is surrounded by a ring of soft-tissue called the labrum; the labrum functions to deepen the socket and thus stabilize the humeral head in the socket.
In addition, a series of ligaments, which also serve to help stabilize the shoulder, attach to the labrum.
Shoulder instability occurs when the head of the humerus slips either partially out of the socket (this is called subluxation), or comes completely out of the socket (this is called a dislocation). Shoulder instability usually initially occurs secondary to a sudden traumatic episode involving the shoulder. The shoulder sometimes slides back into the socket spontaneously, but occasionally it must be put back into the socket (also called “reduced”) by the patient himself or by another person, such as an emergency room physician.
During an instability episode (either a subluxation or dislocation) a variety of structures may be damaged in the shoulder. Typically a tear of the labrum occurs (this tear is called a Bankart lesion); often the stabilizing ligaments are stretched or torn; and occasionally a fracture of the bone of either the ball and/or socket may occur. In older patients (> age 40), tears of the rotator cuff may also occur (see Rotator Cuff Tear).
Signs & Symptoms:
During the actual dislocation episode, the patient usually experiences severe pain. Often there is an obvious deformity of the shoulder region. Once the shoulder is reduced into position the pain usually subsides. Patients may notice numbness and tingling in parts of their hand or shoulder after a shoulder dislocation.
Once the pain from the initial episode resolves, many patients can gradually return to activities with no difficulties. Some patients, however, report fear or apprehension with the shoulder in a certain position, such as if one is cocking the arm and preparing to throw a ball. Other patients have episodes in which the shoulder dislocates again intermittently.
Diagnosis:
The diagnosis of shoulder instability is typically made by the patient’s history and the findings on physical examination. The structural damage to the shoulder is then further defined by a combination of x-rays and additional imaging studies, such as a CT scan and/or an MRI scan.
Treatment:
The treatment of shoulder instability typically depends on the age of the patient and the number of dislocations sustained. Young patients and patients involved in contact or competitive sports may benefit from surgery after the first dislocation episode to stabilize the shoulder.
For most other patients, non-operative treatment is recommended after the first instability episode. This usually includes a sling with a short period of rest, followed by a course of physical therapy, and gradual return to activities. If additional dislocation or subluxation episodes are experienced, these patients also benefit from surgery to stabilize the shoulder.
