The labrum is a fibrocartilagenous ring surrounding the glenoid, or socket. The function of the labrum is similar to the rim of a golf tee. It serves to deepen the socket to help stabilize the ball within the socket. Damage to the labrum may result in instability (looseness) or pain.
The shoulder joint proper is composed of the humeral head (ball) and the glenoid (socket). The humeral head is the top portion of our humerus, or arm bone. The glenoid is the outside portion of our scapula, or shoulder blade. The humeral head is round. The glenoid is flat. Therefore, there is inadequate stability provided to the humeral head by the glenoid proper.
The image to the right shows a shoulder in which the ball, or humeral head, has been removed. The labrum surrounds the entire periphery of the glenoid, or socket. The labrum consists of a form of cartilage called fibrocartilage, or scar cartilage. This durable doughnut of tissue functions like the rim of a golf tee, aiding in providing stability to the humeral head.
Attachments to the Labrum
A number of critical anatomic elements anchor to the labrum. Excessive or repetitive tension to these structures may result in tearing of the labrum.
The long head of the biceps (biceps) originates from the top or superior aspect of the labrum.
Tears involving the long head of the biceps attachment are coined superior labrum or SLAP tears. These tears often develop from falls or overhead sports (swimming, baseball, or volleyball).
Tears of the labrum from the front-top aspect originate from the long head of the biceps or ligaments (superior/middle glenohumeral ligaments (SGHL)). These can occur with falls or sports.
Tears of the labrum from the front-bottom portion of the glenoid typically occur with a dislocated shoulder. This particular tear is coined a Bankart lesion. The major stabilizing ligaments of the shoulder attach to this portion of the labrum, the inferior glenohumeral ligaments (IGHL).
Tears of the posterior labrum can occur either from a dislocation, fall, or overhead sports. Tears cause laxity of the capsule at the top-back portion or the inferior glenohumeral ligament (IGHL) at the bottom-back portion of the shoulder.
Posterior Labral Tear and Instability
Certain dislocations, falls, sports, and repetitive overhead sports can cause a posterior labral tear. Similar to a SLAP tear, a posterior labral tear can be ignored if asymptomatic. Diagnosis is made by history and physical exam. MRI with dye injected into the shoulder is 90% accurate to help confirm the diagnosis.
The success rate of treating isolated symptomatic posterior labral tears without surgery is unknown. Many professional athletes including swimmers and baseball pitchers have large tears and function at a high level without pain. Therefore, most shoulder specialists recommend a trial of rest, ice, activity avoidance, and physical therapy. If pain persists following nonoperative measures, an individual can live with the discomfort or choose to undergo surgical treatment. Individuals continuing to dislocate despite physical therapy should proceed with surgery. The one group of athletes where initial surgical treatment should be contemplated are football lineman.
Surgery is very successful in preventing repeat subluxations and dislocations and eliminating pain. This procedure must be done arthroscopically. The success rate of surgery is approximately 90%.
Following surgery, the arm is maintained in a sling for one month. This allows bone ingrowth into the labrum to take place. Physical therapy begins at one month following the operation to restore motion and regain strength. Contact sports are allowed at six months postoperatively.
Surgery is performed in the following steps.
1) The labral tear and instability is confirmed.
2) The attachment site for the labrum is cleaned of scar tissue so the labrum and bone can grow back together.
3) Anchors are placed in the glenoid. These are bioabsorbable screws with stitches attached.
4) Sutures are looped around the labrum and the capsule. Knots are tied reattaching the labrum to the bony edge of the socket.
There is a final category of individuals with shoulder pain who have loose shoulders yet no labral tears. Typically, this involves a teenager in an overhead sport such as swimming. These individuals have a different tissue composition than "normal" individuals. Teenagers have a higher percentage of Type III collagen than adults. Collagen is the building block of our ligaments, and type III collagen is more elastic than type I, or the normal type. Ligaments and capsule therefore are more elastic than those teenagers that are not hyperlax. The overall volume of the shoulder is much greater than the "normal" individual.
The net effect is individuals with hyperlax ligaments rely on muscles to help provide stability more than normal. Overaggressive training and competition may cause the supporting muscles to fatigue. Since the capsule and ligaments are lax, the shoulder can sublux (slip) and the capsule and/or rotator cuff may get trapped and pinched. This may lead to pain not only with activity, but even with day to day activities.
Diagnosis is made with history and physical examination. MRI examinations usually don't show any major damage. Treatment focuses on relieving pain with normal activities first and foremost, and later the goal is to get the individual back to sport. Initial treatment consists of anti-inflammatories and rest. As this improves, physical therapy focusing on restoring the stabilizing muscles of the shoulder blade and rotator cuff commences. Rarely, corticosteroid injections may be employed. Athletic endeavors are started once pain with simple activities is eliminated and the rotator cuff has regained its protective strength.
The success rate of nonoperative measures to calm down the inflamed shoulders in this scenario is 80%. Individuals continuing to have pain need to make a difficult decision. Those with mild discomfort but good strength and no pain with daily activity can play through without doing permanent damage. Those with pain with simple tasks either need to permanently quit the offending activity or consider operative treatment.
Surgery involves plicating, or suturing, the loose ligaments and capsule. This restores the normal volume of the shoulder. The rotator cuff and shoulder blade muscles therefore don't have to work "overtime" as they did before surgery.
The success rate of surgical treatment for multidirectional instability is between 80-90%. Individuals without a torn labrum have approximately an 80% success rate while those with a torn labrum have closure to a 90% success rate. The hyperlax tissue plicated has a slightly increased propensity to stretch.
Surgery involves rasping the ligaments and capsule to create a bleeding response. Suture anchors then are placed in the socket, and sutures then are fed through the ligaments and capsule.
Knots are tied folding the ligaments and labrum on top of themselves. This is continued until a normal "bumper" and volume of the labrum and capsule has been restored.
Following surgery, the arm is maintained in a sling for one month. This allows the labrum and ligaments to heal in their new shortened position. Physical therapy begins at one month following the operation to restore motion and regain strength. Swimming and other overhead sports begin six months following surgery, but it may take an additional few months to achieve the endurance needed to return to swimming and/or pitching. Other sports or overhead work is allowed at four months following surgery.