Author: BrianLowell, MD, CAQSM
Description
- The anatomy of the glenohumeral (GH) joint is complex, and stability is provided from combination of the capsule, tendons, muscles, bones, and the labrum:
- Labrum acts by increasing surface area for humeral head contact.
- Provides attachment site for GH ligament and the tendon of the long head of the biceps
- Composed of fibrocartilage and dense fibrous collagenous tissue
- The superior aspect is more mobile than the inferior portion that is tightly attached to the glenoid rim.
- Multiple anatomic variations exist: congenitally absent portions of the labrum, different anchor sites for the GH ligament, different biceps tendon origins, and superior labral recesses (1).
- There are currently 10 described SLAP lesions (superior labrum anterior-to-posterior), of which the four originally described by Snyder are the most common:
- Type I is degenerative fraying of the labrum.
- Type II is a detached labral/biceps complex.
- Type III is a bucket-handle tear.
- Type IV is a bucket-handle tear with extension into the biceps tendon (2).
- SLAP lesions occur as acute injuries or with chronic degradation.
Epidemiology
- Incidence of SLAP lesions is relatively low, occurring in approximately 3–6% of all arthroscopic shoulder cases.
- Reported to occur in up to 25% of patient with symptomatic shoulder instability
- More common in men than women
- Most commonly seen in individuals in their mid-20s
Etiology and Pathophysiology
- SLAP lesion development consists of an internal rotation deficit, tightening of the posterior capsule, posterior superior GH shift, maximization of external rotation forces at the biceps anchor and superior labral attachment, and “peel back” of the labrum. Alterations in scapular movements (dyskinesis) exacerbate this mechanism (1).
- Mechanisms of injury to the glenoid labrum occur via acute trauma or repetitive microtrauma from overhead motions:
- Acute mechanism of injury:
- Compression due to a fall on an outstretched arm or onto an adducted shoulder
- Traction injury from a swift pull
- Humeral head shearing such as during vehicle accidents from seat belt restraint
- Chronic mechanism of injury:
- Secondary to repetitive motions that result in micro trauma accumulation
- Chronic instability
Risk-Factors
- Repetitive overhead motions (sports or occupational):
- Shoulder instability/trauma
- Anatomic variation or underlying generalized laxity/instability
General Prevention
- There are no definitive guidelines for prevention of SLAP lesions. Generally, physical therapy practices are followed:
- Rotator cuff strengthening
- Scapular stabilizer strengthening
- Posterior capsule stretching
- Limiting internal rotation deficits
- Ensuring proper overhead mechanics
- Additionally, monitoring pitch counts in the youth has been implemented as a preventative technique.
Commonly Associated Conditions
Labral tears are commonly associated with other underlying shoulder problems, as forces that cause labral injuries can cause other pathology. Thus, a high index of suspicion is required when evaluating for SLAP lesion, as other shoulder pathology coexist in approximately 85% of cases (Bankart lesions, GH instability, rotator cuff, and bicipital tendon pathology). This can significantly confound the diagnosis.