What are the initial diagnostic tests for shoulder instability?

Initial Diagnostic Tests for Shoulder Instability

The initial diagnostic evaluation for shoulder instability should include specific provocative maneuvers such as the anterior apprehension test, relocation test, anterior drawer test, load-and-shift test, and sulcus test, followed by plain radiographs in three planes as the first-line imaging modality. 1, 2

Clinical Examination Tests

Primary Provocative Tests

• Anterior Apprehension Test:

  • Most specific test when using apprehension (not pain) as the positive criterion
  • Sensitivity: 72%, Specificity: 96%, Likelihood ratio: 20.2 3
  • Technique: Patient's arm is brought into abduction and external rotation

• Relocation Test:

  • Highly specific follow-up to the apprehension test
  • Sensitivity: 81%, Specificity: 92%, Likelihood ratio: 10.4 3
  • Technique: Posterior force applied to proximal humerus during apprehension test

• Anterior Release/Surprise Test:

  • Demonstrates the best overall sensitivity and specificity 4
  • Technique: Sudden release of stabilizing posterior force during relocation test

Additional Valuable Tests

• Anterior Drawer Test:

  • Can be performed successfully in 87% of patients
  • Sensitivity: 53%, Specificity: 85%, Likelihood ratio: 3.6 3
  • Positive when it reproduces the patient's instability symptoms

• Load-and-Shift Test:

  • Evaluates the amount of translation of the humeral head on the glenoid 2

• Sulcus Test:

  • Specifically useful for identifying inferior instability
  • Important for diagnosing multidirectional instability 2

• Bony Apprehension Test:

  • Screens for significant bony lesions causing instability
  • Positive when apprehension occurs at or below 45° abduction and 45° external rotation
  • Sensitivity: 100%, Specificity: 86% for detecting bony lesions 5

Imaging Studies

Initial Imaging

• Plain Radiographs:
  • Should be obtained in three planes as the first imaging study 1, 6
  • Useful for identifying fractures and bony abnormalities
  • Can detect Hill-Sachs defects and bony Bankart lesions
  • Limited sensitivity (50%) for bony lesions compared to arthroscopy 5

Advanced Imaging (if needed)

• MR Arthrography:

  • Gold standard for diagnosing labral tears
  • Sensitivity: 86-100%
  • Especially valuable in patients under 35 years of age 1

• Standard MRI without contrast:

  • Highly effective with optimized imaging equipment
  • Recommended if radiographs are negative and symptoms persist 1

• CT Arthrography:

  • Third choice, only if MRI is contraindicated
  • Comparable to MR arthrography for Bankart and Hill-Sachs lesions 1

Clinical Pearls and Pitfalls

• Interpretation Pitfall: Using pain rather than apprehension as the criterion for positive apprehension and relocation tests significantly reduces their diagnostic value 3

• Examination Challenge: Pain may limit the ability to perform the anterior drawer test in some patients (13%) 3

• Diagnostic Algorithm:

  1. Start with provocative maneuvers (apprehension, relocation, and release tests)
  2. Proceed to plain radiographs in three planes
  3. If radiographs are negative but clinical suspicion remains high, order MR arthrography
  4. Consider CT arthrography only if MRI is contraindicated

• Direction Assessment: Carefully differentiate between anterior, posterior, or multidirectional instability as treatment approaches differ significantly 6

• Bony Lesion Detection: The bony apprehension test is more sensitive than plain radiographs for detecting significant osseous lesions (100% vs 50%) 5