The Shoulder Labrum: Three Zones of Injury

Function

The shoulder is the most mobile joint in the body. Shaped as a ball and socket, the shoulder or Glenohumeral Joint has two main components, the top of the arm’s Humerus (ball shaped) and the oval shaped concavity of the Glenoid (socket), projecting from the shoulder blade. The labrum is a rubbery-like lining to the Glenoid, similar in configuration to a tire on a wheel. The labrum prevents dislocation of the shoulder, especially in the frontward or anterior direction. The labrum also acts as a dynamic or mobile tensioning device, while serving as the attachment point for the bicep tendon as it travels up the arm and through the shoulder.

 

Labral Injuries can be categorized into three main ‘zones’ which are detailed below:

1.  Anterior Labral Injury – The word anterior is used to refer to the front of the shoulder. Injury to the front of the shoulder’s lining is usually the most obvious type of labral injury to diagnose. Often occurring in the setting of a trauma or shoulder dislocation, patients with this injury tend to feel unstable. They will often complain of apprehension, or the feeling that the shoulder is going to slide out of the socket with certain motions, especially when reaching out to the side, or overhead.

2. Posterior Labral Injury – The antonym of the word ‘anterior,’ posterior labral injury refers to the back of the shoulder’s lining. Injury in this area is much less obvious than anterior injury, because injury to the back of the shoulder rarely, if ever, causes instability. This is due to the presence of large and robust rotator cuff muscles that sit directly behind the posterior labrum, preventing a dislocation, even when the labrum itself is injured. Patients with posterior injury often experience a vague ache or pain which is deep within the shoulder, but also hard to identify. Of the three zones of labral injury, posterior lesions are the most commonly missed, as the symptoms are often non-specific and attributed to general weakness or inflammation.

3. Superior Labral Injury – The superior labrum, or top portion of the shoulder’s lining, is unique in providing an attachment point for the bicep tendon. This area (the biceps attachment) is a common pain generator in patients with shoulder pain. Injury to the top of the labrum commonly occurs in athletes participating in sports involving swinging (golf, tennis) and throwing (baseball/softball). Performing such motions with improper form can result in a front to back injury of the superior labrum, commonly known as a ‘SLAP tear.’ Fortunately, early diagnosis and treatment of improper form will prevent SLAP injury, allowing for pain free return to play.

Author
Elan Golan, MD

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