Labrum: A Latin word you will hear, here and there, around the hip, and around the shoulder. Did you know that the word “Labrum” means “lip (or lip-like)”? Many individuals with shoulder pain are told that they have a torn labrum, usually based on an imaging study called magnetic resonance (MRI). The tricky part is to figure out if a labrum that looks torn on MRI is actually the culprit. As you will see below, it can be very confusing!
What is the shoulder labrum?
The shoulder joint is formed by the upper round portion of the bone in the arm (a sphere called humeral head) and the socket (glenoid) on the outer part of the shoulder blade. As mentioned when we discussed the Latarjet procedure, the humeral head is much larger than the socket. It has been compared to a golf ball on a golf tee. This discrepancy in size is what allows the shoulder such ample range of motion, but it also makes the shoulder somewhat at risk for the ball to fall out of the socket (i.e., the joint can dislocate).
The labrum is a lip-like structure made up with the same tissue that forms the meniscus of the knee joint: fibrocartilage. It is firm but flexible. The labrum helps maintain the humeral head within the confines of the socket: it makes the socket dish wider and deeper, and also acts as a retaining wall to some extent. The labrum is intimately connected to most of the socket rim (it is like they are glued together). The biceps muscle in the front of the arm has two portions on its shoulder end; one of the portions (called the long head) enters the shoulder joint and melts into the labrum.
How is the labrum torn?
A portion of the labrum can become torn (“unglued”) off of the socket rim. When the front of the labrum is torn (anterior labral tear), it is almost always the consequence of an anterior shoulder dislocation. The back of the labrum can be torn (posterior labral tear) in a posterior shoulder dislocation as well, but it more commonly tears secondary to multiple small injuries that jam the humeral head to the back (this classically happens to defensive linemen that try to block players all day long with the hands in the front). These anterior and posterior tears will be discussed some other time. Today we will focus on tears of the superior labrum (right around the top of the socket, where the long head of the biceps melts into the labrum).
Superior labral tears are also known as SLAP tears (the Superior Labrum tears from Anterior to Posterior). In some individuals, SLAP tears are the result of an accident that drives the humeral head into the superior labrum, such as a fall on the outstretched arm or with the arm forcefully rotated. Some believe that a sudden biceps pull can also rip the labrum (this can happen serving a tennis ball or spiking a volleyball). In older individuals, labrum tears are part of an overall aging and arthritic process involving the shoulder joint; these are called degenerative labral tears. Superior labral tears can be felt as painful episodes of catching. When the labrum is torn, fluid can leak from the joint through the rent and collect in a cyst (paralabral cyst). These cysts can become painful, and even compress an adjacent nerve (the suprascapular nerve). Pressure on this nerve is painful as well and can lead to weakness and atrophy of one or two of the rotator cuff muscles on the top and back of the shoulder.
A SLAP tear? Help me with the diagnosis, please…
Magnetic resonance (MRI) has become the image modality of choice to visualize a tear in the labrum (short of arthroscopic surgery, of course). On MRI, the normal labrum presents a triangular cross-section and looks dark (has low signal). An area of linear brightness at the junction between the labrum and the socket rim is accepted as indicator of a labral tear. However, a couple of problems complicate the diagnosis of a SLAP tear on MRI. The first problem is that these changes on MRI signal can also be due to small normal changes in the structure of the labrum, and not a tear. The second problem is that as we all age, our labrum degenerates along the rest of the joint, making it difficult to know if the torn labrum is truly responsible for pain, or just one more hallmark of arthritis. This is the bottom line: just because your labrum is reported to be torn on MRI, it does not mean a SLAP tear is the reason for your shoulder pain; in fact, your labrum may not even be torn! Hence, you need to have your shoulder examined by a shoulder specialist.
The chances of a labral tear to be the real problem in your shoulder increase if you are younger, if your symptoms clearly started after an accident or injury, if you experience mechanical symptoms (such as catching or locking), if there is weakness or atrophy of your rotator cuff, and if the MRI shows a paralabral cyst in addition to a tear. You can try to self-diagnose yourself using the so-called active compression test (see video below). Place your arm in front of you with your elbow extended, your hand in line with your face, and your thumb pointing down. Use your other hand to try to bring your bad arm down while resisting it. SLAP tears are usually painful on the back of the shoulder with this maneuver, and pain improves if the same maneuver is repeated in exactly the same position, but by with the hand facing up. You can have someone help you by being the one applying force down. As with many other test, the active compression test is not perfect. Your shoulder specialist will perform this and other tests that all together can solve the puzzle and determine if your torn labrum is painful. In some instances, the diagnosis can only be confirmed or excluded with arthroscopic surgery.
What is the treatment?
If the labrum is truly torn and painful, it seldom heals on its own. However, some individuals improve substantially with a steroid injection inside the shoulder joint, and by avoiding aggravating activities. Large cysts can also be aspirated. However, a number of individuals end up needing surgery.
There are two surgical ways to solve the symptoms of a torn superior labrum. If the labrum is torn but otherwise pristine, and the long head of the biceps is absolutely normal, then most surgeons would consider a labral repair. An arthroscopic camera is introduced into the shoulder joint, one or two anchors with sutures are inserted into the socket rim, and the sutures are used to tie down the labrum to the socket. Three to four weeks of immobilization are typically required for the labrum to start healing; therapy starts at that point. If there is a cyst, the liquid filling the cyst can be removed. Occasionally, the suprascapular nerve also needs to be released, but that is a whole other story.
Unfortunately, as we all get older, the risk of stiffness increases if a torn labrum is repaired. This is particularly true for degenerative tears: making the joint tighter will aggravate arthritic symptoms. Another way to solve the symptoms of a torn labrum is to cut the long head of the biceps off the labrum: once the biceps is no longer pulling on the labrum, many patients get better. This is particularly helpful in patients with a labral tear that extends into the biceps, or when the biceps is substantially frayed and inflamed. Simply cutting the biceps (biceps tenotomy) improves pain, but the biceps muscle in the front of the arm will look funny to some extent (pop-eye deformity), and it may occasionally cramp. Alternatively, the cut long head of the biceps can be fixed in a different location in the humerus (biceps tenodesis); this prevents deformity and cramping, but prolongs recovery time. Your shoulder surgeon will discuss what is best for you: a labral repair, a biceps tenotomy or a biceps tenodesis.