Shoulder Posterior Stress Test

Posterior Stress Test (or Posterior Apprehension test) of the shoulder is used to test for Posterior Instability.

How to perform Shoulder Posterior Stress Test?

The patient is in a supine or sitting position. The examiner elevates the patient’s shoulder in the plane of the scapula to 90° while stabilizing the scapula with the other hand. The examiner then applies a posterior force on the patient’s elbow. While applying the axial load, the examiner horizontally adducts and medially rotates the arm.

If the test is done with the patient in the sitting position, the scapula must be stabilized

What does a positive Posterior Apprehension test mean?

A positive result is indicated by a look of apprehension or alarm on the patient’s face and the patient’s resistance to further motion or the reproduction of the patient’s symptoms. A positive test indicates a posterior instability or dislocation of the humerus.

Pagnani and Warren reported that pain production is more likely than apprehension in a positive test. They reported that with atraumatic multidirectional (inferior) instability, the test is negative.

Notes

The test should also be performed with the arm in 90° of abduction. The examiner palpates the head of the humerus with one hand while the other hand pushes the head of the humerus posteriorly. Translation of 50% of the humeral head diameter or less is considered normal, although results vary. If the humeral head moves posteriorly more than 50% of its diameter, posterior instability is evident. The movement may be accompanied by a clunk as the humeral head passes over the glenoid rim.

The most characteristic sign for a shoulder posterior dislocation is a loud clunk as the shoulder is moved from a forward flexed position into abduction and external rotation, a positive finding that is often misdiagnosed as an anterior dislocation.

The findings for a posterior dislocation are usually severe pain, limited ER, often to less than 0 degree, and limited elevation to less than 90 degrees.

Patients who have a posterior instability pattern typically report symptoms with the arm in a forward flexed, adducted position, such as when pushing open heavy doors.

There is usually a posterior prominence and rounding of the shoulder as compared to the opposite side, and a flattening of the anterior aspects of the shoulder. Looking down at the patient’s shoulders from behind can best assess these asymmetries.

Reference

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