Shoulder Orthopaedic Test: Internal Rotation Lag Sign

The internal rotation lag sign is a clinical test used to assess the integrity of the subscapularis muscle and tendon, which is one of the four muscles of the rotator cuff. The subscapularis muscle is responsible for internal rotation of the shoulder joint.

Procedure:

1. Ask the patient to sit or stand with their arm behind their back, elbow flexed to 90 degrees.
2. Stand behind the patient and grasp their forearm just above the wrist with one hand, while placing your other hand on their opposite shoulder to stabilize it.
3. Passively externally rotate the patient's arm, maintaining the elbow flexed to 90 degrees, until the forearm is parallel to the ground.
4. Instruct the patient to hold their arm in this externally rotated position while you release your support.
5. Observe the patient's ability to maintain the arm in the externally rotated position without any difficulty.
6. If the patient is unable to maintain the arm in the externally rotated position and it "lags" or falls back toward their side, it may indicate a subscapularis muscle or tendon tear.

A normal result of the internal rotation lag sign test is the patient's ability to maintain the externally rotated position without any difficulty. This suggests that the subscapularis muscle and tendon are intact.

The sensitivity and specificity of the internal rotation lag sign test for detecting subscapularis tendon tears vary widely across studies, with reported values ranging from 33% to 100% for sensitivity and 91% to 100% for specificity. These discrepancies in sensitivity and specificity may be due to differences in the populations studied, variations in the technique used to perform the test, and variations in the definition of a positive test.

References:

1. Bak, K., & Cameron, E.A. (2010). The clinical value of the lag signs in diagnosing rotator cuff tear. Journal of Shoulder and Elbow Surgery, 19(1), 27-31. doi: 10.1016/j.jse.2009.06.002
2. Gomberawalla, M.M., Miller, E.S., & Knesek, M. (2017). Shoulder examination: A systematic approach. American Family Physician, 95(9), 556-562.
3. Jobe, F.W., Jobe, C.M., & Kvitne, R.S. (1989). Intraarticular and subacromial shoulder injections. Operative Techniques in Sports Medicine, 1(1), 1-15. doi: 10.1016/S1060-1872(89)80038-5
4. Magee, D.J. (2014). Orthopedic Physical Assessment (6th ed.). St. Louis, MO: Elsevier Health Sciences.
5. Park, H.B., Yokota, A., Gill, H.S., El Rassi, G., McFarland, E.G., & Liang, K.P. (2005). Diagnostic accuracy of clinical tests for the different degrees of subscapularis tears. Journal of Bone and Joint Surgery - American Volume, 87(11), 2527-2531. doi: 10.2106/JBJS.D.02480