External Rotation Lag Sign (ERLS) Test

Original Editor - Alan Jit Ho Mak

Top Contributors - Alan Jit Ho Mak, Amanda Ager and Anas Mohamed  

Purpose

This is a shoulder special test which is meant to assess the integrity and tears of the supraspinatus (SSP) and infraspinatus muscles (muscles which collectively contribute to the rotator cuff complex). This test can also be used for the clinical examination of a shoulder impingement syndrome (SIS).  

Another name for this test is the Infraspinatus Spring Back Test.  

This test assesses for the presence of reported pain, weakness and integrity in the infraspinatus and SSP muscles.  

The instructions

Supraspinatus muscle.png
1.    The patient is seated and the elbow is passively flexed to 90 degrees while the shoulder is held at 20 degrees elevation in the scapular plane in a position of near maximum external rotation (i.e., maximum external rotation minus five degrees to avoid an elastic recoil effect). If your patient is able to hold this position, this indicates a negative test. For a positive test howeve;, your patient would not be able to hold this position and their arm may spring back anteriorly, indicating that the teres minor and the infraspinatus are weak or painful.  

2.   The examiner supports the elbow and holds the arm in external rotation at the wrist. 

3.   The patient is asked to hold the position while the examiner supports the elbow but releases the hold at the wrist. 

4.   The degree of movement is estimated and is referred to as the “lag” (i.e., the difference between active and passive ROM). 

Instructional Video

[1]

Sensitivity / Specificity

As a reminder, the sensitivity of a clinical test is its ability to identify individuals with a specific pathology (the ability of the test to rule-in an injury or clinical diagnosis). The specificity of a clinical test is its ability to identify individuals who are not affected by a specific pathology (the ability of the test to rule-out an injury or clinical diagnosis).[2]

A cohort study has concluded that the Lag Sign has a sensitivity of 97% and a specificity of 93% for full thickness tairs of the infraspinatus muscle. A sensitivity of 100% and a specificity of 93% for full thickness tears of the teres minor muscle.[3]

Technique Criticism

The External Rotation Lag Sign (ERLS), described by Hertel et al[4] in 1996, has been widely accepted as a valid test for the diagnosis of tears involving at least the infraspinatus muscle. More recently, the test has been re-evaluated. In a population with a low pre-test probability for supraspinatus tears, the test has been confirmed to be both highly specific and moderately sensitive for an isolated supraspinatus tear, when the surgeon or clinician is looking for small degrees of a lag. 

Some concerns are still present regarding the use of the ERLS in the diagnosis of an isolated supraspinatus tear. The reasons for the skepticism could be found in the relative absence of scientific data and clinical studies to support the use of the ERLS. This may be due to the difficulty in reproducing the ERLS in a laboratory setting.[5]

In a study where 40 participants with rotator cuff pathology, they concluded that ERLS will be negative in patients with hypertrophy of teres minor in the setting of a postero-superior cuff tear. Hence, there is a strong correlation between the presence of a rotator cuff tear and the hypertrophy of the teres minor muscle.[6]  Another study has also concluded that the ERLS is potentially able to detect an isolated SSP tear if the test is performed correctly (20 degrees of abduction). The deltoid and biceps muscles are almost silent during the performing of this clinical test, limiting some potential confounding factors. 

References

  1. External Rotation Lag Sign Available from:https://www.youtube.com/watch?v=AzDQ9s3qipg [last accessed 23/11/2020]
  2. Cochrane UK (2020)https://uk.cochrane.org/news/sensitivity-and-specificity-explained-cochrane-uk-trainees-blog. Accessed: 22 Nov 2020.
  3. Castoldi F, Blonna D, Hertel R. External rotation lag sign revisited: accuracy for diagnosis of full thickness supraspinatus tear. Journal of Shoulder and Elbow Surgery. 2009 Jul 1;18(4):529-34.
  4. Hertel R, Ballmer FT, Lambert SM, Gerber CH. Lag signs in the diagnosis of rotator cuff rupture. Journal of Shoulder and Elbow Surgery. 1996 Jul 1;5(4):307-13.
  5. Blonna D, Cecchetti S, Tellini A, Bonasia DE, Rossi R, Southgate R, Castoldi F. Contribution of the supraspinatus to the external rotator lag sign: kinematic and electromyographic pattern in an in vivo model. Journal of shoulder and elbow surgery. 2010 Apr 1;19(3):392-8.
  6. Vella S, Rao AS. Relation between hypertrophy of teres minor muscle and external rotation lag sign in patients with rotator cuff pathology. Indian journal of orthopaedics. 2019 Jun;53:392-5.