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.
SLAP (Superior Labral) Tears
Our biceps muscle has two tendon origins. One is from a portion of the shoulder blade called the coracoid, and the other is confluent with the superior labrum. Tearing of the superior labrum can occur from falls or overhead sports. Repetitive pull on the biceps from throwing, swimming, or hitting may cause the top portion of the labrum to pull away from the glenoid.
There are no known long-term consequences from having a superior labral tear. If one has a SLAP tear, yet no pain and no limitation of function, then it would be advisable to live with the tear. Symptomatic tears can present with either pain with overhead sports (swim, throw, etc.), pain with lifting objects, or frank instability. Rotator cuff tendonitis and/or tears often may coexist with a SLAP tear.
Diagnosis of a SLAP tear is not straightforward. History and physical exam approximately are 70% accurate in diagnosing a SLAP tear. MRI exams without contrast (dye) are 50-70% effective in diagnosing a tear while those with an injection in the shoulder (arthrogram) are 70-90% accurate. Many times SLAP tears are found incidentally at the time of surgery for other labral repair procedures or rotator cuff surgery.
The success rate of treating isolated symptomatic SLAP tears 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. Occasionally, anti-inflammatories in the form of pills and/or corticosteroid shots are used. The treatment rationale is to relieve discomfort from a rotator cuff tendonitis and improve shoulder mechanics, shoulder stability, and tight tissue with physical therapy. If pain persists following nonoperative measures, an individual can live with the discomfort or choose to undergo surgical treatment.
Arthroscopic surgery to fix a SLAP tear is performed as an outpatient procedure.
1) A general anesthetic is given. Occasionally an interscalene block is given to numb the nerves supplying pain sensation to the shoulder and the arm. A standard shoulder arthroscopy is performed.
2) The labral tear is identified. The arm is placed in a position to determine if the biceps will pull the labrum away from the socket. A probe confirms the labral tear.
3) Soft tissue from the labral attachment site is removed. Bone from the socket therefore is exposed. This allows the bone and labrum to grow together.
4) Anchors are placed in the glenoid underneath the cartilage. An anchor is comprised of a bioabsorbable screw with suture material. The screw component is placed deep to the cartilage surface.
5) Sutures are looped around and underneath the torn labrum.
6) Knots are tied plastering the torn labrum against the prepared socket.
Following surgery, the arm is maintained in a sling for one month. This allows bone ingrowth from the socket into the labrum to take place. Physical therapy begins at one month following the operation to restore motion and regain strength. Sport specific therapy (i.e. swimming and throwing) begins at four 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 four months following surgery. Surgery is 90-95% successful in restoring normal function and minimizing pain, however overhead athletes may only have a 80% success rate returning to the previous level of sport.