Empty Can Test

Empty can test or as it called Jobe Supraspinatus Test is used to check for weakness or insufficiency of the supraspinatus muscle and rotator cuff impingement of the shoulder. It was first described by Christopher M. Jobe, MD, an Orthopedic surgeon in Oroville, California.

How do you perform the empty can test?

Empty can test may be performed with the patient standing or seated, with the examiner stands facing the patient. The examiner hand is placed on the superior portion of the midforearm to resist the motion of abduction in the scapular plane.

With the elbow extended, the patient’s arm is held at 90 degrees of abduction, 30 degrees of horizontal flexion, and in internal rotation. The examiner exerts pressure on the upper arm during the abduction and horizontal flexion motion. It is important to apply pressure gently at first and to increase the pressure only if pain has not been triggered during the course of the test to that point.

Using electromyography EMG, this test enables testing of the supraspinatus muscle largely in isolation.

Although this test isolates the supraspinatus muscle-tendon unit, clinical weakness can be simulated by the presence of significant pain. To alleviate some of this pain and to more directly evaluate supraspinatus strength, the test can be repeated with the thumbs pointed upward (the “full can” position) the so called a full can test.

See Also: Rotator Cuff of the Shoulder

Full Can Test

Full Can Test is done with the patient standing or sitting. Similar to the empty can test, the elbow is extended and the patient’s arm is held at 90° of abduction, 30° of horizontal flexion, and in external rotation. Then the examiner applies a pressure on the examined limb.

A positive test occurs when asymmetric weakness occurs involving the affected shoulder.

This variation of the Jobe test is thought to reduce the pain associated with supraspinatus impingement and may be more sensitive to actual weakness rather than guarding due to impingement.

This maneuver is thought to position the greater tuberosity away from the coracoacromial arch and may therefore decrease the pain associated with mechanical cuff impingement.

What does a positive Empty Can Test mean?

When Jobe Test elicits severe pain and the patient is unable to hold his or her arm abducted 90° against gravity, this is called a positive drop arm sign. If the test elicits pain and the patient is unable to abduct the arm 90° and hold it against gravity, this indicates a tear of the tendon of the supraspinatus muscle, or damage to the suprascapular nerve.

The Empty Can Test may be repeated at only 45° abduction to further differentiate the findings.

The superior portions of the rotator cuff (supraspinatus muscle) are particularly assessed in internal rotation (with the thumb down as when emptying a can), and the anterior portions in external rotation (thumb points upward – full can).

Where the impingement component predominates, there will be less pain and more strength where the tendon is still intact.

The Empty Can Test can yield false-positive results where pathology of the long head of the biceps tendon is present.

Strength in the supraspinatus muscle may not be completely diminished until over two-thirds of the tendon is torn.

Empty Can Test Accuracy

A Cohort Study ¹ by Nitin B Jain found that empty can test had a high sensitivity and specificity for supraspinatus tears as following:

• Sensitivity: 88 %
• Specificity: 62 %

Another study ² found the empty can test to have a high sensitivity of 86% and a low specificity of 50% in diagnosing supraspinatus tendon tears in a series of 55 patients.

The full can test had higher specificity (74% vs. 68%) and an equal sensitivity of 77% when compared with the empty can test in a series of 136 patients ³.

Diagnostic Utility of the Empty Can Test in Identifying Subacromial Impingement:

Population	Reference Standard	Sensitivity	Specificity	+LR	-LR
Pooled estimates from six studies (n = 695)	Impingement syndrome diagnosed by arthroscopy	.69 (.54, .81)	.62 (.38, .81)	1.8	.50
55 patients with shoulder pain	Impingement diagnosed via arthroscopy	.50 (.26, .75)	.87 (.77, .98)	3.9 (1.5, 10.1)	.57 (.35, .95)

Notes

Studies performed by anesthetizing the suprascapular and axillary nerves show that the supraspinatus and deltoid muscles are responsible for abduction of the arm. The supraspinatus muscle, along with the other muscles of the rotator cuff , press the head of the humerus into the socket and abduct the arm for the first 20°, then the deltoid muscle comes into play. Even if the supraspinatus muscle tendon is completely torn, the shoulder is still capable of good range of motion. There is a deficit only at the onset of abduction and then again when the arm reaches 90° and above.

EMG tests show no difference in the EMG activity whether the arm is held in full internal rotation (classic Jobe empty can position), with the thumb pointing to the floor, or with the arm in maximum external rotation (full can position). The strength of the supraspinatus muscle can also be tested with the elbows flexed rather than extended, for the patient, this position requires less holding power and less stress, and is therefore also less painful.

A partial rupture of the supraspinatus tendon will result in abduction that is both weak and painful. A painless weakness with abduction could indicate a complete rupture of the supraspinatus tendon, although the deltoid cannot be ruled out. The tendon of the supraspinatus can be passively stretched by positioning it in adduction and IR to see if this increases the pain.

Eccentricity of the humeral head in the form of superior displacement of the humeral head in a rotator cuff tear causes relative insufficiency of the outer muscles of the shoulder. Small tears that can be functionally compensated for will cause minor loss of function with the same amount of pain. Larger tears are invariably characterized by weakness and loss of function.

The empty can test and full can test are about equally accurate in detecting supraspinatus tears. Because the full can test is less pain provoking of impingement symptoms, its use is recommended. Pain in the absence of weakness does not help detect partial-thickness tears or tendinopathy.

Related Anatomy

There are four rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis muscles).

Supraspinatus muscle originates from Superior scapula and inserts onto Humerus Greater tuberosity. It’s innervated by Suprascapular nerve.

Its action is abducting and externally rotating the arm, providing stability to the shoulder joint.

References

1. Nitin B Jain, Jennifer Luz, Laurence D Higgins, Yan Dong, Jon J P Warner, Elizabeth Matzkin, Jeffrey N Katz. The Diagnostic Accuracy of Special Tests for Rotator Cuff Tear: The ROW Cohort Study.Am J Phys Med Rehabil. 2017 Mar. PMID: 27386812.
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3. Itoi E, Kido T, Sano A, Urayama M, Sato K. Which is more useful, the “full can test” or the “empty can test,” in detecting the torn supraspinatus tendon? Am J Sports Med. 1999 Jan-Feb;27(1):65-8. doi: 10.1177/03635465990270011901. PMID: 9934421.
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