Rotator Cuff Injuries
Anatomy of Shoulder
The rotator cuff is a group of muscles and their tendons that act to stabilize the shoulder. The head of the upper arm bone (humeral head) rests in a shallow socket in the shoulder blade called the glenoid that is much smaller than the head of the upper arm bone. A soft, fibrous tissue rim called the labrum surrounds the socket to help stabilize the joint. The rim deepens the socket by up to 50% so that the head of the upper arm bone fits better. In addition, it serves as an attachment site for several ligaments.
The rotator cuff muscles also perform multiple functions, including abduction, internal rotation, and external rotation of the shoulder. This cuff of cartilage makes the shoulder joint much more stable, yet allows for a very wide range of movements, far exceeding any other joint in the body. The tendons at the ends of the rotator cuff muscles can become torn, leading to pain and restricted movement of the arm. A torn rotator cuff can occur following a trauma to the shoulder or it can occur through the “wear and tear” on tendons, most commonly the supraspinatus tendon.
Common Causes of Rotator Cuff injuries
Rotator cuff injuries are commonly associated with motions that require repeated overhead motions or forceful pulling motions. Such injuries are frequently sustained by athletes whose actions include making repetitive motions. Injuries to the tissue rim surrounding the shoulder socket can also occur from acute trauma such as:
- Falling on an outstretched arm
- A direct blow to the shoulder
- A sudden pull, such as when trying to lift a heavy object
- A violent overhead reach, such as when trying to stop a fall or slide
- Throwing athletes or weightlifters can experience glenoid labrum tears as a result of repetitive shoulder motion.
Types of Rotator Cuff Injuries
The labrum is made of a thick collagenous tissue that is susceptible to injury. It also becomes more brittle with age and can fray and tear as part of the aging process.
Symptoms of a labral tear depend on where the tear is located, but may include:
- An aching sensation in the shoulder joint
- Catching of the shoulder with movement
- A sense of instability in the shoulder
- Decreased range of motion
- Loss of strength
SLAP Tears are a type of labral tear most commonly seen in overhead throwing athletes such as baseball players and tennis players. It is also common in weightlifters. The torn labrum seen in a SLAP tear is at the top of the shoulder socket where the biceps tendon attaches to the shoulder. The upper end of the biceps muscle has two tendons that attach it to bones in the shoulder.
Biceps tendon tears.
Many tears do not completely sever the tendon and can be treated with regenerative medical procedures. A complete tear will split the tendon into two pieces. In many cases, torn tendons begin by fraying. As the damage progresses, the tendon can completely tear.
The long head of the biceps tendon is more likely to be injured. This is because it is vulnerable as it travels through the shoulder joint to its attachment point in the socket. Fortunately, the biceps has two attachments at the shoulder. The short head of the biceps rarely tears. Because of this second attachment, many people still use their biceps even after a complete tear of the long head, disguising the need for treatment.
Bankart Tears are a specific type of labral tear sustained when a person dislocates the shoulder. As the shoulder pops out of joint, it often tears the labrum, especially in younger patients. The tear is to part of the labrum called the inferior glenohumeral ligament.
Posterior Labral Tears are less common, but sometimes seen in athletes in a condition called internal impingement. In this syndrome, the rotator cuff and labrum are pinched together in the back of the shoulder.