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Special Test

External Rotation Lag Sign

External Rotation Lag Sign is used to check for the integrity of the supraspinatus and infraspinatus tendons of the rotator cuff of the shoulder.

How do you perform External Rotation Lag Sign?

  • The patient is seated with his or her back to the examiner.
  • The elbow is passively flexed to 90 degrees, and the shoulder is held at 20° of abduction and near maximal external rotation (maximal external rotation minus 5 degrees to avoid elastic recoil in the shoulder) by the examiner.
  • The patient is asked to maintain the position of external rotation actively as the examiner releases the wrist, while maintaining support of the arm at the elbow.
  • The same test can be repeated with the arm abducted to 90°, which specifically tests the infraspinatus and teres minor muscles.

What does a positive External Rotation Lag Sign mean?

  • External Rotation Lag Sign is positive when a lag, or angular drop, occurs.
  • If the patient cannot hold the arm in the position into  which it was passively placed (submaximal external rotation with slight abduction) and it reverts to the internally rotated position, then this indicates a lesion of the supraspinatus tendon.
  • If the position cannot be held at 90° abduction, the test is highly sensitive and specific for a lesion of the teres minor muscle.

Sensitivity & Specificity

A comparative study by Filippo Castoldi1 to reassessed the sensitivity and the specificity of the external rotator lag sign (ERLS) for diagnosis of supraspinatus tears in a large cohort of patients. He found that the External Rotation Lag Sign is highly specific and acceptably sensitive for diagnosis of full-thickness tears of the rotator cuff, even in case of an isolated tear of the supraspinatus tendon:

  • Sensitivity: 56 %
  • Specificity: 98 %

A study on 37 patients with shoulder pain (Supraspinatus or infraspinatus tear diagnosed via ultrasound), the External Rotation Lag Sign has a sensitivity of 46% and a specificity of 94%, while the Drop Arm Test has a sensitivity of 73% and a specificity of 77%.

Another study by Hertel et al.2 reported 70% Sensitivity and 100% Specificity with this test , but the study had a potential for bias.

Notes

A study by Davide Blonna3 concludes that the External Rotation Lag Sign is potentially able to diagnose an isolated supraspinatus tendon tear if the test is performed correctly (20 degrees of abduction). The deltoid and biceps muscles are almost silent during the test, limiting confounding factors.

Related Anatomy

Supraspinatus Muscle:

  • The Supraspinatus Muscle originates from the superior scapula and inserts onto Greater tuberosity of the humerus.
  • It’s action include Abducting and externally rotating arm, providing stability to the shoulder joint.
  • Its innervation comes from the Suprascapular nerve.

Infraspinatus Muscle:

  • The infraspinatus Muscle originates from the Dorsal scapula and inserts onto Greater tuberosity of the humerus.
  • It’s action include Providing stability to the shoulder joint and externally rotating the arm.
  • Its innervation comes from the Suprascapular nerve.
Rotator Cuff muscles
Rotator Cuff muscles

Reference

  1. Filippo Castoldi, Davide Blonna, Ralph Hertel: External rotation lag sign revisited: accuracy for diagnosis of full thickness supraspinatus tear. J Shoulder Elbow Surg . Jul-Aug 2009;18(4):529-34. PMID: 19223205.
  2. Hertel R, Ballmer FT, Lombert SM, et al: Lag signs in the diagnosis of rotator cuff rupture. J Elbow Shoulder Surg Am 5:307–313, 1996.
  3. Blonna D, Cecchetti S, Tellini A, et al. Contribution of the supraspinatus to the external rotator lag sign: kinemtic and electromyographic pattern in an in vivo model. J Shoulder Elbow Surg 2010;19(3):392–398. PMID: 20056454.
  4. Miller CA, Forrester GA, Lewis JS. The validity of the lag signs in diagnosing full-thickness tears of the rotator cuff: a preliminary investigation. Arch Phys Med Rehabil. 2008;89:1162-1168.
  5. Clinical Tests for the Musculoskeletal System 3rd Edition.
  6. Dutton’s Orthopaedic Examination, Evaluation, And Intervention 3rd Edition.
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