What is Empty Can Test?
Jobe and Moynes originally described the Empty Can Test (ECT). Therefore, it is also known as the Jobe’s test. The empty can test or jobe’s test is used to study, examine or assess the supraspinatus muscle and the supraspinatus tendon located in the shoulder complex. In other words, it is used to determine injury to the supraspinatus muscle or supraspinatus tendon.
The supraspinatus muscle is one of the four muscles of the rotator cuff. A rotator cuff is a group of 4 muscles and their tendons. These muscles include supraspinatus, infraspinatus, teres major and subscapularis.
The main function of the supraspinatus and the deltoid muscle is to perform abduction of the shoulder. Weakness of the shoulder abduction can be attributed to supraspinatus muscle or deltoid muscle injury or pathology. The jobe’s or empty can test isolates the supraspinatus muscles and checks its strength, integrity, and function independent of the deltoid muscle.
How do you perform an Empty Can Test?
Position of the patient
- The patient can be either in a sitting or standing position.
- Both the arms of the patients are raised to 90 degrees in the scapular plane.
- The arms are then fully internally rotated so that the thumbs point towards the floor as if the patient were draining liquid out of a can.
Role of the examiner
- Once rotated, the examiner then applies a downward directed force to the arm, and the patient is instructed to resist this force.
The empty can test is considered positive if there is pain, weakness or both are present during resistance. A positive empty can test indicates a tear in the supraspinatus tendon or muscle or neuropathy of the suprascapular nerve.
Boettcher, ginn showed that the Empty Can Test activates supraspinatus muscle at a level of approximately 90% MVC using normalized EMG. Other shoulder muscles were also activated at similar levels, including the upper subscapularis and infraspinatus, scapular positioning muscles (upper, lower and middle trapezius and serratus anterior), and abduction producing muscles (anterior and middle and posterior deltoid). All these muscles were activated to the same levels.
Researches reveal that the best position for the maximal isolation of the supraspinatus muscle is best achieved when the scapula is elevated or raised to 90° in the scapular plane and +45° external rotation of the humerus (full can position).
However, as explained above, the EMG studies show that the supraspinatus muscle is not adequately isolated in the empty can tested position (fully internal rotation) due to the high activation of the many other shoulder muscles simultaneously. Therefore, a question arises on the validity of the empty can test for the diagnosis of the supraspinatus pathology.
The empty can test has a sensitivity ranging from 74% to 88% and specificity ranging from 30% to 58%.