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 below 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.
Anterior Labral Tears/Anterior Shoulder Dislocations and Instability
Shoulder dislocations can result from a fall from a height or from a strong hit during an athletic event. Typically, a fair bit of force is required to initially dislocate the shoulder. As our arm is brought backwards with regards to the body, the ball can dislocate in an anterior-inferior (front-bottom) direction. The anterior labrum pulls away from the socket. The ligaments anchoring into the labrum remain loose.
In the figure below, a camera is looking directly onto the socket from the top looking at the bottom. The labrum and ligaments typically are intimately attached to the socket. With a dislocation, the labrum pulls away from the socket and heals in an inappropriate position resulting in lax ligaments.
The back portion of the humeral head (ball) remains lodged on the front-bottom portion of the glenoid (socket) while the shoulder is dislocated. This potentially can cause damage to the back/top portion of our humeral head; this is called a Hill-Sachs deformity.
Occasionally, other injuries can accompany an initial dislocation. Injuries include damage to the rotator cuff, fractures to either the socket or humeral head, or nerve damage. Additional diagnostic tests may be needed to determine these injuries.
The biggest concern following an initial dislocation is the redislocation rate. The most critical determination of this is someones age. Teenagers have a higher percentage of loose tissue than do adults. Therefore the redislocation rate for a teenager is at least 50% while that of an adult is probably 25-30%. A teenager involved in a contact sport (football, hockey, wrestling, etc.) has a redislocation rate of 90%.
Most orthopaedic surgeons agree that nonoperative treatment is appropriate for an adult engaging in noncontact activities. However, there is debate regarding the appropriate course of action for a contact athlete or teenager dislocating their shoulder for the first time. Repeated dislocations have to potential to cause the following:
Further tearing of the labrum
Further stretching of the ligaments and capsule
Enlarge or create a Hill-Sachs lesion.
Development of arthritis
The shoulder increasingly becomes likely to redislocate even with trivial activity as more dislocations occur. Aggressive or overhead sports therefore will be avoided to prevent further dislocations and/or subluxations.
Surgery is recommended for recurrent dislocators or individuals at high risk following their first time. The likelihood of these people redislocating approach 80-90%. High-risk individuals include the following:
Thirteen to sixteen year old without loose, or hyperlax, tissue
Teenager playing a contact sport
High-level contact athlete (Collegiate or professional)
Nonsurgical treatment involves a two to three week period of resting the shoulder in a sling. Physical therapy focusing on strengthening the shoulder blade and rotator cuff muscles begins. Return to full athletic endeavors is allowed when adequate motion and strength have been achieved.
Surgery involves the following steps.
1) The labral tear is identified. The labral tear is freed up and all scar tissue is removed. The attachment site on the glenoid is freshened.
2) Anchors are placed in the glenoid. These are bioabsorbable screws with stitches attached.
3) Sutures are looped under the labrum.
4) Knots are tied fastening the labrum to the socket. The labrum and ligaments are retensioned. Over the next few months the labrum and the bone from the socket grow back together.
Surgery is very successful in preventing repeat dislocations and restoring motion. Arthroscopic surgery (repair through poke holes) has the advantage of providing stability with minimizing loss of rotation often seen with an open procedure. The success rate of surgery after a single dislocation is approximately 95% while that after numerous dislocations drops to at least 90-95%. As previously mentioned, repeated dislocations cause further stretching of the ligaments and capsule. This makes it more difficult to restore the tension of the shoulder surgically, and repairs have a slightly higher propensity to stretch out excessively. An extremely large Hill-Sachs lesion (or worn away bone on the humeral head) makes the success rate of an arthroscopic procedure significantly less than that of an open procedure, and in certain instances an open procedure (formal large incision) may be advisable.
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.