What is Posterior Labral Tear?
A posterior labral tear is also known as reverse bankart lesion is a very rare shoulder condition that has a high occurrence rate in individuals involved in sports such as football, swimming, wrestling, weight lifting, or manual labour.
Unlike anterior shoulder injuries, posterior-related injuries account for only a fraction of the shoulder related injuries.
When there is repeated exposure to the posterior region of the shoulder from shear forces from the outside, the head of the humerus causes the posterior to move out of the glenoid, causing a tear in the fibrous tissue known as the labrum. This also affects the structures surrounding it such as the glenohumeral ligament and the adjacent capsular.
What causes posterior labral tear?
The most common mechanism resulting in posterior labral tear is repetitive microtrauma to the posterior capsulolabral complex. Shear force to the posterior region of the shoulder when the arm is flexed and internally rotated and adducted is a very likely cause.
Glenoid retroversion due to bony defects can result in instability and recurrent dislocation can disrupt the inherent static and dynamic stabilizers of the glenohumeral joint is also a plausible cause.
What are the symptoms of a posterior labral tear?
Generally, a labral tear is very painful and causes swelling. Other symptoms include:
- Unable to perform overhead motions like serving a tennis ball
- Popping or clicking in the shoulder when performing overhead motions
- Weakness in the shoulder, lifting objects may seem like a challenging task
- Limited range of motion and instability in the shoulder
- Feeling as if the bone may pop out of the socket when flexed and abducted
- Unable to perform high-velocity movements resulting in a subpar performance in sports
- Discomfort in sleeping due to the constant pain in the posterior region
Usually, a posterior labral tear always occurs with other shoulder injuries such as dislocated shoulders, rotator cuff injuries, or torn biceps tendons.
Diagnosis of posterior labral tear
A posterior labral tear can be a bit difficult to diagnose as it sometimes presents itself with other shoulder injuries. Therefore, the doctor will thoroughly look into the medical history of the patients and the activities involved.
This will be followed by a detailed physical examination of the injured shoulder to assess the pain and swelling. The doctor will also conduct tests to come to a clear diagnosis. These tests include:
- Posterior Apprehension Test: In this test, the doctor will flex the patient’s elbow to 90 degrees and abduct the patient’s shoulder to 90 degrees maintaining neutral rotation. The doctor will then slowly apply external rotation force to the arm to 90 degrees. If the patient shows an unwillingness to move the arm the test result comes out as positive. The patient’s apprehensiveness and not pain are considered positive result.
- Posterior Load and Shift Test: In this test, the doctor stabilizes the scapula with one hand and places the other hand on the posterior glenohumeral joint line, humeral head, and the space across the patient’s acromion. The index finger is on the glenohumeral joint. Now the doctor will apply a load and shift of the humeral head in the posterior direction to assess posterior instability.
- Jerk Test: While stabilizing the scapula with one hand and holding the affected arm at 90 degrees abduction and internal rotation, the doctor will grasp the elbow and axially load the humerus in the proximal direction moving the arm horizontally across the body. If a sudden clunk sound is heard as the humeral head slides off the back of the glenoid, the result is positive.
- Kim Test: In this test, the doctor will stabilize the scapula and slowly abduct the arm at 90 degrees, and forward flex it to 45 degrees. Then the doctor will apply force posteriorly and inferiorly. If the patient experiences pain, the result is positive. This test is highly sensitive and is specifically made for a posterior labral tear.
The next step will be X-rays and MRI scans. X-rays hardly show any damage caused to tissues but show posterior shoulder dislocations and help rule out the possibilities of other shoulder related problems. MRI scans help in detecting the damage caused to the labrum and the glenohumeral ligaments.
Treatment for a posterior labral tear
The initial line of treatment for posterior labral tear is often non-surgical. This includes:
- Sufficient rest and avoiding activities that may aggravate the pain should be avoided.
- Non-steroidal anti-inflammatory medicines as prescribed by the doctor should be taken.
- Physical Therapy focusing on strengthening and flexibility of the shoulder should be performed under the expert guidance of the therapist.
If non-surgical methods fail to provide satisfactory results arthroscopic surgery by the doctor is likely to be performed.