The shoulder joint is a ball (Humeral head) and socket (Glenoid) type of joint. The glenoid (socket) is quite shallow and cannot maintain the humeral head (ball) in place on its own. The glenoid is surrounded by the labrum which deepens the glenoid providing for stability of the shoulder joint. Several ligaments are also attached to the labrum, hence injury to the labrum affects the overall stability of the shoulder joint.
This labrum can be torn as a result of an injury such as a shoulder dislocation or by wear and tear (due to overuse). The anterior labrum is torn in an anterior dislocation and the posterior labrum is torn in a posterior dislocation. Posterior dislocations are more common in electrocution and epileptic seizures.
This can lead to instability of the shoulder where you can feel as if your shoulder is loose and popping out of place. These symptoms are more common in younger individuals who are more active particularly with regard to sports. Repeated dislocation can lead to erosion of the anterior aspect of the glenoid and the posterolateral part of the humeral head (Hill-Sach's lesion) and increases the tendency of the shoulder to dislocate.
A good history and physical examination usually provides a clear cut diagnosis. An apprehension test will be performed whereby the shoulder is placed in a position which causes it to dislocate. A patient who has experience of recurrent dislocations will be apprehensive with this manoeuvre and tries to resist the position. There can also be increased translation of the humeral head in relation to the glenoid.
Most of the times, the cause is unknown, but it can happen in rheumatoid arthritis, hypothyroidism, pregnancy, previous wrist fractures, tumours or cysts within the wrist, infection or burns. It can also occur in diabeticswhich may be due to problems with the nerve as a part of peripheral neuropathy rather than compression of the nerve.
Xrays are of little value in diagnosing this condition unless the labral tear is associated with a small avulsion fracture of the glenoid. An MRI or MR arthrogram can reveal the position and extent of the tear. It can also reveal any other concomitant injuries within the shoulder.
Initial treatment following a shoulder dislocation is to immobilize the shoulder for 3-4 weeks to rest the shoulder and allow the soft tissue to heal. This is then followed by physical therapy to regain shoulder movements and also to strengthen the shoulder musculature.
If inspite of this treatment, the shoulder continues to dislocate, then your doctor will advise you to undergo surgery to help improve the stability of the shoulder. This is in the form a repair of the labrum to the glenoid. This is commonly done nowadays as an arthroscopic procedure, however can also be done by an open technique through a longer incision. The open technique is associated with a longer recovery time. The labrum is repaired using an implant called a suture anchor which is inserted into the bone. The other end contains sutures which are passed through the torn labrum and aids repair. Usually 3 such suture anchors are necessary for a satisfactory repair.
However, if there is significant glenoid erosion and humeral head defect due to recurrent dislocations, then your doctor may recommend an open procedure such as a Latarjet procedure instead. Results of the Latarjet procedure are equally good. Here the coracoid process (another part of the scapula or shoulder blade bone) is detached and reattached to the anterior part of the glenoid using screws. This increases the width of the glenoid and resists the humeral head from slipping out.
Rehabilitation is an extremely important part of treatment especially after surgery. These surgeries are usually followed by a period in sling with only passive range of motion allowed initially for about 4-6 weeks. Active motion is then allowed after this followed by strengthening.