The shoulder is one of the most mobile joints in the human body, allowing for a remarkable range of motion. This versatility comes at the expense of stability, making the joint susceptible to injury. The shoulder’s ball-and-socket structure relies on surrounding soft tissues to maintain its integrity. A common injury to this stabilizing structure is a tear to the labrum, which can result in pain and functional limitation.
Anatomy of a SLAP Tear
The shoulder joint is formed where the head of the humerus (upper arm bone) meets the glenoid, a shallow socket on the shoulder blade. Surrounding the glenoid is a ring of specialized fibrocartilage called the labrum. This tissue functions to deepen the socket by up to fifty percent, creating a more secure fit for the humeral head and providing an attachment point for various ligaments and tendons.
A SLAP tear affects this cartilaginous rim. The acronym SLAP stands for Superior Labrum Anterior to Posterior, defining the location of the damage. This tear occurs in the superior (top) portion of the labrum and extends from the front (anterior) to the back (posterior) of the socket.
The superior labrum is important because it is where the long head of the biceps tendon attaches to the shoulder joint. A SLAP tear often involves the biceps tendon anchor, which affects the joint’s function and stability. Forces exerted by the biceps muscle are directly transmitted to the torn tissue, often contributing to symptoms.
Mechanisms of Injury
A SLAP tear typically results from two primary forces: acute trauma or repetitive strain. Acute injuries often occur when falling onto an outstretched arm, which drives the humeral head up into the superior labrum, causing a compression injury. Other traumatic events, such as a motor vehicle collision or a sudden, forceful pull, can also lead to an immediate tear.
Repetitive microtrauma is another common cause, particularly in athletes who perform frequent overhead movements, like baseball pitchers or weightlifters. In throwing athletes, the intense external rotation required during the late cocking phase of a throw creates a twisting force on the biceps tendon, known as the “peel-back” mechanism. This torsional stress peels the labrum away from the glenoid bone, leading to a tear.
For middle-aged and older adults, a SLAP tear is often a gradual process rather than a single injury. Over time, the labrum can fray and degenerate as a normal part of aging, making the tissue more susceptible to tearing from minor stresses. These degenerative changes represent a different injury mechanism than the acute trauma seen in younger, athletic populations.
Symptoms and Diagnostic Tools
Patients with a SLAP tear often report a deep, aching pain inside the shoulder joint that is difficult to pinpoint. This discomfort is aggravated by specific movements, especially lifting the arm overhead or reaching across the body. Throwing athletes may complain of a noticeable decrease in pitching velocity or a “dead arm” feeling after activity.
A common mechanical symptom is clicking, popping, or grinding within the shoulder during movement, indicating that the torn labral flap is catching in the joint. Some individuals also experience instability or a feeling that the shoulder is going to slip out of the socket, particularly when the arm is placed in an abducted and externally rotated position.
Diagnosing a SLAP tear begins with a thorough physical examination, where a physician will test the shoulder’s range of motion, strength, and stability. Specific provocative maneuvers, such as the O’Brien’s test, are performed to reproduce the patient’s pain and help isolate the injury to the labrum. The definitive confirmation of a SLAP tear usually requires advanced imaging.
Standard X-rays rule out fractures but cannot visualize the soft tissue of the labrum. The most reliable diagnostic tool is a Magnetic Resonance Imaging (MRI) scan with contrast, known as an MR arthrogram. This procedure involves injecting a dye directly into the joint space, which highlights the tear by seeping into the gap between the torn labrum and the glenoid.
Treatment Options
Initial management for most SLAP tears begins with conservative, non-surgical approaches. This typically involves rest and the use of nonsteroidal anti-inflammatory drugs to reduce pain and inflammation. A structured physical therapy program is fundamental, focusing on restoring full range of motion and strengthening the rotator cuff and periscapular muscles.
Physical therapy aims to compensate for the damaged labrum by improving the dynamic stability of the shoulder. For many patients, especially those with smaller or degenerative tears, symptoms can resolve within three to four months with focused rehabilitation. If conservative treatment fails, surgical intervention may be considered.
Surgery for a SLAP tear is minimally invasive and performed arthroscopically, utilizing small incisions and specialized instruments. The surgical strategy depends on the nature of the tear, the patient’s age, and activity level. For a repairable tear in a young, active patient, the surgeon re-attaches the torn labrum to the glenoid bone using small anchors and sutures.
When the biceps tendon attachment is significantly involved or in older patients, the surgeon may opt for a procedure called a biceps tenodesis. This involves detaching the long head of the biceps tendon from the superior labrum and re-anchoring it to a different location on the humerus. This procedure removes the painful forces pulling on the torn labrum, providing reliable pain relief. Recovery typically takes several months.