What is the empty can test?

The Empty Can Test: A Clinical Assessment for Supraspinatus Pathology

The empty can test is a clinical examination maneuver used to assess supraspinatus muscle function, but it does not selectively activate the supraspinatus muscle and should be interpreted alongside other clinical findings rather than as a definitive diagnostic test for supraspinatus pathology. 1

Technique and Performance

The empty can test is performed as follows:

• Position the patient's arm at 90 degrees of abduction
• Add 30 degrees of forward flexion (scapular plane)
• Internally rotate the shoulder fully (thumb pointing downward, as if emptying a can)
• Apply downward resistance while the patient attempts to maintain the position

Diagnostic Value

Sensitivity and Specificity

• The empty can test demonstrates high sensitivity (81%) for detecting supraspinatus tears 2
• However, it has limited specificity compared to other tests like the drop-arm test or Patte test 2
• The test shows a low negative predictive value (0.58), meaning a negative test doesn't reliably rule out pathology 2

Electromyographic Evidence

• EMG studies show that the empty can test does not selectively activate the supraspinatus muscle 1, 3
• During the test, significant activation occurs in:
  • Supraspinatus
  • Infraspinatus
  • Middle deltoid
  • Multiple other shoulder muscles 1

Comparison with Other Tests

• The "full can" test (same position but with thumb up) is an alternative that may cause less impingement pain 4
• The hug-up test has demonstrated higher sensitivity (94.1%) with comparable specificity (76.6%) for supraspinatus tears 5
• For optimal diagnostic value, combining tests improves accuracy - the Neer sign combined with the drop-arm test shows the best diagnostic odds ratio (12.92) 2

Clinical Application

Optimal Use

• Most effective when positive for both pain AND weakness (diagnostic odds ratio of 10.45) 2
• Should be used as part of a comprehensive shoulder examination rather than in isolation
• Most valuable when combined with other clinical tests and imaging when appropriate

Limitations

• Does not satisfy basic criteria to be a valid diagnostic tool for supraspinatus pathology when used alone 1
• Activation of multiple shoulder muscles limits its specificity 3
• Muscle activation patterns are influenced by arm position and elevation plane 4

Practical Considerations

• The test may be beneficial during shoulder muscle strengthening programs despite diagnostic limitations 1
• When evaluating rotator cuff pathology, consider using multiple tests rather than relying on a single maneuver
• The test's high sensitivity makes it useful as a screening tool, but positive results should be confirmed with additional testing or imaging

For accurate diagnosis of supraspinatus tears, clinicians should consider combining the empty can test with other physical examination maneuvers and correlating findings with appropriate imaging studies when indicated.